Systematic Survey on Digital Still Cameras

2
Motokazu Ohkawa

 Abstract
Imaging is a culture that only humans can freely make use of as a means of communicating information, andfrom ancient times – even prior to the birth of civilization – we have exchanged, communicated, and recorded
information by means of images.
The camera was invented and has evolved as a tool for recording images easily and accurately.
Although the origin of the camera goes back to the camera obscura, which was used to draw a picture by tracing
an image focused on a screen in a dark box through a pinhole or a lens, since the advent of the Daguerreotype, thefirst real camera, which was announced in 1839, until the early 2000s, cameras have developed as tools forrecording images using a photochemical reaction technique.
It was during 1981 that an electronic camera was announced that converted captured images to electronic signals
by means of an image sensor and recorded them to a dedicated floppy disk. Known as the “Floppy Camera,” thiswas the first camera to record images using a method other than the photochemical reaction technology employedwith conventional silver halide cameras.
However, the still images grabbed from the analog video signal by the Floppy Camera, which appropriated thetechnologies employed in existing video cameras to view images on a TV screen, was unable to produce images ofsufficient quality to replace conventional cameras.
At almost the same time, Toshiba announced a prototype that recorded images digitally, and unlike the traditional
analog technology used in electronic cameras, which suffered from dropout in the recording and reproduction
stages, the digital signal processing techniques employed actually improved image quality. However, as image
playback was slow due to the recording media (audio cassette tape) and poor image compression technology
employed, and the fact that images were displayed on a TV screen, it was of no real practical use.
In the late 1980s, flash memory, a type of large-capacity non-volatile semiconductor storage, was developed anda digital still camera (DSC) that electronically recorded digital image signals on such media was announced.
However, this too was unable to replace silver halide cameras due to poor image compression efficiency, theextremely high cost (1 million+ JPY), and image quality that was still just enough for viewing on a TV screen andnot high enough for printing purposes.
JPEG, a high-efficiency/high-performance image compression technology, was established as an international
standard in 1992, the same year that Japan proposed its use as a standard for consumer DSCs. At the same time, theprice of memory dropped and Casio's launch of the QV-10 at a price of 65,000 JPY in 1995, followed by the
QV-10A at 49,800 JPY in 1996, triggered the expansion of the consumer DSC market.
During the mid-1990s, with the rapid popularization of the personal computer and the advent of the internet,
exchanging images electronically became more common, and the development of digital electronic appliances, suchas DTVs and DVDs, brought on the Digital Information Age.
The DSC is not simply a device that records images electronically rather than using the photochemical method
employed with conventional silver halide cameras, but has established itself as an image-capturing peripheral in adigital environment that is capable of interacting with computers, the internet and printers. Furthermore, as DSCs
are designed to work with PCs rather than being confined to working with TVs, restrictions in terms of image size
have been removed, and image quality has remarkably improved to the extent that DSCs have quickly come toreplace silver halide cameras, with total annual sales and production exceeding those of silver halide cameras in2000 and 2002 respectively. Today, DSCs boast annual sales in excess of 1 trillion JPY and the technologies andformats developed for DSCs have already been transferred into mobile phones, opening up yet another new market:
image communication devices.
It should be noted that the DSC, which was born in Japan and has gone on to conquer world markets, was made a
reality by the various technologies developed by Japanese industries. Furthermore, as Japanese electronics
manufacturers pioneered this field, they have made it possible for Japan to maintain leadership in this market, andwith the standardization of DSC specifications, consumers will no longer put off buying products for reasons of
future incompatibility, and DSC manufacturers are free to concentrate on improving their technology within an
established framework.

 Profile
Motokazu Ohkawa
Chief Researcher, Center of the History of JapaneseIndustrial Technology, National Museum of Natureand Science

1
2
3
4

1962

5
6
7

1988
1991

1995
2000
2007

2

 Contents

Graduated from the Physics Department of
Tohoku University's Faculty of Science andthe same year joined Tokyo Shibaura ElectricCo., Ltd. (now known as Toshiba
Corporation), where he was engaged in the
research of acoustics at the company's Central
Research Laboratory. After that he wasengaged in the development of CATV, etc., at
the Consumer Electronics Research Center.
Engaged in digital camera development.
Digital Camera Technology Committee
Chairman of JEITA (Japan Electronics andInformation Technology Industries
Association) (originally JEIDA: Japan
Electronic Industries Development
Association). ISO TC42 expert.
Relocated to the High-tech Visual Promotion
Center.
Camera & Imaging Products Association(CIPA) technical adviser.
Resigned from CIPA. Chief Survey Officer,
Center of the History of Japanese Industrial
Technology, National Museum of Nature andScience until stepping down at the end of
March 2008.
Chairman of the Japan Color Standardization
Committee (JSA) during that time.

Introduction .................................................... 3
The History of Image Culture ........................ 5
Digital and Fourier Transform ....................... 8
The History of the Camera ........................... 13

DSC Structure .............................................. 25
DSC Characteristics ..................................... 31
DSC-Related Technology and
Systematization ............................................ 36
8 Image Compression and Formats ................. 53
9 Standardization of DSCs .............................. 65
10 The Future of DSCs ..................................... 68
11 Discussion and Acknowledgements ............. 74
DSC Genealogy .................................................. 77
Appendix 1. List of significant models. ............. 78
Appendix 2. Chronology .................................... 79

National Museum of Nature and Science Technology Systematization Survey Report Vol.10 2008.March

1 Introduction
Only humans use images as a means ofcommunicating
information,andcommunicating information by means ofimages is something that is unique to humanculture. Thirty thousand or more years ago,
our ancestors created an image culture toconvey information through images and toleave a record of their feelings. Over the
centuries, humans have devised anddeveloped ways of more easily and accurately
creating and saving images.
As a result of such efforts, while on one
hand this led to the birth of the “pictorial art
culture,” which sought to be more artistic, on
the other hand it led to the advent of the“camera culture,” which sought a greater
degree of accuracy.
The history of cameras is said to havebegun approximately 170 years ago with theannouncement of the Daguerreotype in 1839.
Since then, over the course of more than 150
years, using the silver halide photochemical
reaction, cameras have been the means bywhich images of subjects have been recorded;in other words, they have gone throughvarious technological revolutions as the silver
halide film camera. During the early 1980s,
however, electronic cameras appeared thatelectronically recorded images, and by theend of the 1980s, digital still cameras (DSCs)
had been announced that recorded images asdigital signals in semiconductor memory.
Characteristics of early DSCs included thefact that they were instant, that there was no
deterioration in quality when transferring or
copying images, and that they had few
moving parts. They were designed for
displaying images on TV screens and image
quality was by no means comparable withthat of existing silver halide film cameras.
However, one of the features of DSCs isthat they handle images as digital information,
which means that images are easy to use on
computers and peripheral devices. As society
quickly embraced the personal computer andtechnological infrastructure was developed
making things such as digitization and theinternet a reality, the market for IT-related

electronic devices rapidly expanded andconsumer-level digital appliances, such as
DSCs, flourished. Moreover, DSCs fusedwith mobile phones to create newcommunication tools, resulting in thedramatic advancements in image-based
communications.
In addition to the abovementioned
development of the digital information
environment, the background to the rapid
development of DSCs included technologicalinnovations such as memory and image
sensor-related semiconductor technology andimage processing technology, such as the
JPEG format. However, special mention
needs to be made of the fact that DSC
development originated in Japan, that thestandardization of international standards was
carried out at the initiative of Japan, and thatJapan basically held a monopoly on themarket. There are very few such examples in
the consumer equipment market.
Furthermore, the camera market, which had
been monopolized by the traditional camera
manufacturers as the conventional precision
machinery industry, became the launching
pad for electronic equipment manufacturers,
who were experts in electronics and softwaredevelopment, to launch out into the DSC
market in quick succession. On account of
this, the camera market, where up until thattime product cycles had been long, withflagship models being used in some cases for
decades, saw a shortening of product cycles,
which forced camera manufacturers toshorten development time, resulting in a pricewar. Therefore, radical reform was requiredon the part of camera manufacturers
producing conventional silver halide film
cameras. In light of this, it could be said that
DSCs caused an industrial revolution in thecamera industry.
In this document, we will focus on DSCs asa modern hit product developed withJapanese initiative. In Chapter 2 we will
examine history leading up to thedevelopment of the camera, while in Chapter
3 we will look at digital technologies.
Systematic Survey on Digital Still Cameras

3

Continuing on in Chapter 4, we will examine
the historical flow leading up to thedevelopment of the DSC, followed by asimple explanation of DSCs in Chapter 5, andin Chapter 6 we will look at thecharacteristics of DSCs.
In Chapter 7, I will mention DSC-related
technology from the perspective of thesystematization of technology. Chapter 8 willdeal with the compression standards andformats that are characteristic of DSCs.
I will explain the present state of DSC
standardization in Chapter 9 and look at
possible future directions for DSCs in
Chapter 10 and systematically explain thehistory of the changes in technologicaldevelopment and product development led

4mainly by Japan, with the intention of leaving
it as a record for future generations.
In this document I have used the word
“image” to refer to a recorded visualization of
a subject. Although some publications use theterms “image” to refer to pictures and “video”
to refer to movies, where it is necessary todifferentiate in this document, I refer topictures as “still images” and movies as“video.”Furthermore, while conventional cameras
utilizing roll film are referred to in manydifferent ways, such as “still cameras,”“ silver halide film cameras,” “film cameras”
and “SH (Silver Halide) cameras,” etc., inthis document they will be referred to as“silver halide cameras.”

National Museum of Nature and Science Technology Systematization Survey Report Vol.10 2008.March

2 The History of Image Culture
2.1

Image Culture as a Basic
Human Desire

From the time that humans first appearedon the earth, they have created various
tangible and intangible cultures. Among these,
imaging cultures that use images to exchange,
communicate and record information are
noteworthy cultures and nothing similar isobserved with any of the animals. The historyof the development and evolution of thecamera is the history of the technologicalprogress that has supported the history ofimaging cultures.
Unlike words and sentences, images, which
directly appeal to the visual senses, are themost accurate way to communicate
information. As mentioned in 62–60 B.C. byGeneral Zhao Chongguo in The Book of Han,
“Seeing once is better than hearing a hundred
times,” and mankind has known from ancient
times that images can communicate much
more information than any other means [1].
The fact that, for example, the stereo data on
a music CD is only 176.4 kB (each channel is
44.1kHz 16-bit), while the data on a digital
VTR (D2) is approximately 16 MB, meansthat image data is approximately 100 times aslarge as sound data, a fact that can be provenscientifically.
Only humans can use this image data as ameans of communicating information andeven if animals could communicate visually
by expressing actions and expressions, they
are not capable of communicating using
image data by means such as drawing
pictures. In this way we can see that cultureusing images in data communications is anadvanced culture unique to mankind.

2.2

What theRepresent

Caveincluding Jean-Marie Chauvet. Referred to
now as the cave paintings of the
Chauvet-Pont-d'Arc Cave, these cave
paintings, which number in excess of 300 andare thought to have been painted during theUpper Paleolithic period, are estimated to beapproximately 32,000 years old, making themolder than the famous cave paintings of theCave of Altamira in Spain (Fig. 2.2), whichwere previously thought to be the oldest in
the world.
In an age in which it is thought that there
were no letters and language was not as yet
adequately developed as a means ofcommunication, our ancestors are thought tohave used images to describe theirexperiences and other things they wanted toexpress and communicate. Deep inside thecaves, far away from sunlight, these paintings,
which are thought to have been drawn relying
on light from lamps burning animal fat, evennow, tens of thousands of years later, thefeelings of the people who drew them are
adequately communicated to us.

Fig. 2.1. Chauvet Cave wall painting.

Paintings

In 1994, polychrome cave paintings, suchas the one shown in Fig. 2.1, were discovered
in a cave in the département of Ardéche insouthern France by a group of speleologists
Systematic Survey on Digital Still Cameras

5Unlike words and sentences, images, which
directly appeal to the visual senses, are themost accurate form of communicating
information.
When you have seen something or thought
something, although communicating thatthrough gestures, sounds or words issomething that can be seen among the higher
animals other than humans, expressing it
using images is an advanced means of data
communication that only humans are capableof doing.
Communicating in this way using images isa basic human desire and in order to develop
this advanced culture, mankind has developed
many technological innovations in order tomore accurately, more realistically and moreeasily create, communicate and preserve theimages
that
are
their
means
of
communicating information. It could be said
that the pursuit of that desire, together withtechnological development, has supported thewisdom of mankind as an imaging culture,
resulting in the evolution of human society.

2.3

Art and Technology

From ancient times, mankind has createdlandscape paintings and portraits as a meansof passing on image information of existing
people and things to future generations and tocommunicate it to other people. However, notonly does it take time to create pictures toleave such images, but it also requires skill
and proficiency on the part of the people
creating them. Therefore, this gave rise to
specialist artists and repeated technologicalreforms and training to enable more realistic
and more passionate expression. This resulted
in pictures being not simply a means ofleaving images, but developing into

6

Pictures
Camera Obscura

Cave Paintings

Fig. 2.2. Altamira Cave wall painting.

expressions of unique culture.
On the other hand, starting from the camera
obscura, which used the principle of thepinhole camera that had been known before
Christ, photography was invented andevolved as a means of leaving images as
pictures even for people who had no skill.
The English word meaning “photography”
is derived from the Greek words “photos,”
meaning “light,” and “graphein,” meaning “todraw,” being used for the first time by Sir
John F.W. Herschel in 1839 as a word
meaning “to record images using light.”
Photography is a technology for leaving
images as photographs of subjects, and thecamera has developed as a device forphotographing a subject (Fig. 2.3).

Silver Halide Film Camera
Daguerreotype

Cassette Camera
Floppy Camera

Fig. 2.3. Pictures and photographs.
Photographs make it possible to easily andaccurately copy a subject within a shortperiod of time and, compared with the skill
that must be acquired in order to paint a
picture, it is a technique that is easy to learn.
Therefore, it developed as a means ofresponding to the demand for the creation of
accurate images within a short period of time,such as portrait photographs in place of
portrait paintings and landscape photographs
in place of landscape paintings.
As a device for taking photographs,
camerashave
experiencedmanytechnological changes in order to more
simply and accurately produce images withina shorter period of time at a cheaper price.
Advances in photograph were not simply
aimed at taking photographs of subjects moreaccurately, but at developing cameras for
special applications, such as in harshenvironments (high temperature/high pressure,

National Museum of Nature and Science Technology Systematization Survey Report Vol.10 2008.Marchetc.) and underwater.
Furthermore, combining machinery andoptics according to application and purpose
made it possible to produce cameras forapplications such as endoscopes forphotographing the inside of the body where it
is impossible to carry out examinations withthe human eye, and for cameras that can takepanoramic photographs at a wide viewing
angle.
Moreover, advances in technology for use
when taking photographs and in image
processing, such as for recomposing
photographs after taking them and forpost-processing, made it possible to display inphotographic
imagesadegreeofself-expression that it was not possible toobtain simply by photographing a subject,leading to the development of the new fieldof photographic art.
Originally, methods of creating images
with the aim of communicating information
through them were divided into paintings,
which required skill and practice, andphotographs, which were easy for ordinary
people to make, and although the former wereartistically inclined, the latter proceeded in atechnical direction. There were also those
who were technically inclined in terms ofpaintings and computer art, etc., and those
who were artistically inclined in the creationof photographs.
It could be said that mankind has maderepeated advances, from the perspective ofboth skill and technology, with the universal
aim of furthering mankind's imaging culture.
The camera is a device that has been adopted
as a means by which to take part in thisimaging culture.
Note:[1] The Book of Han, General Zhao
Chongguo, “Since seeing once is better
than hearing a hundred times, I would
like to go to the battlefield in person to
draw a map, then bring back some good
advice.”Systematic Survey on Digital Still Cameras

7

3 Digital and Fourier Transform
Before writing more about digital cameras,
let us consider the word “digital” itself.
Although we often hear the word “digital”
used in conjunction with things such as
digital cameras, the first common use of thisword was probably with regard to the digital
watch. Since then, with the popularization ofcomputers, the internet and mobile phones,
etc., the word has come to be part of ourlives.
Generally, it is thought that “digital” is abinary means of expression using “0 or 1,” or“Yes or No,” while by contrast “analog”
expresses phenomena/events continuously.
Furthermore, phrases such as “a digital
person” have also appeared and there is atendency for old-fashioned conservative
things to be referred to as “analog,” while
things that are fresh and innovative arereferred to as “digital.”
The word “digital” is derived from theLatin digitalis, from digitus, meaning “finger,
toe.” It is said to have originally meant“pertaining to the fingers (and/or toes)” in thesense that we count on the fingers and bend
them saying, “one, two, three …” and werefer to the number of “digits.” By contrast,“analog” is derived from the Greek ανάλογος(analogos) meaning “proportional,” andmeans “something that is similar tosomething else in some way.”
For example, “the Caspian Sea has an areaof 371,000 km2” is a digital expression, while“the area of the Caspian Sea is almost thesame as the area of the Japanese Archipelago”
is an analogous expression. While it isdifficult to get a sense of how big it is bysaying that the area is 371,000 km2, sayingthat it is “about the same size as Japan”
means that one can imagine how big it is.
So, while analog is expressed in terms of aphysical quantity, digital is a numericalexpression.
The numerical system that we use in ourdaily lives is the decimal system, which isexpressed using the ten digits 0 to 9. However,the numerical system used by computers isbinary, which consists of the two digits 0 and

81.
Although it is easy for mistakes to occur
due to errors in cases where vague
phenomena are classified in ten categories,classifying them into only two categories iseasy and there are few errors. On account of
this, in the realm of telecommunications, thebinary system is widely used in spite of the
drawbacks of using a large number of digits.
However, as I have already mentioned,
digital originally meant “expression as
discrete values,” and the binary system isnothing more than one type of digital
expression.
Whethertohandlesomethingproportionally or symbolically is not simply amatter of a difference in the means ofexpressing a simple phenomenon, and leads
to a major disparity in human thoughtprocesses and the processes involved inprocessing subject matter.
On one hand, an analog is a physicalquantity, working directly on the humansenses. This is the equivalent of a painted
picture (which is handled as a physicalphenomenon) as opposed to a written
expression. This can also be seen in
Buddhism, where the exterior of things isreferred to as “entity.”On the other hand, a digital expression is an
enumeration of numbers, through which wecannot sense any physical meaning. Only
when we understand the way in which thenumbers are arranged can we for the firsttime understand the meaning of a digital
signal.
With DSCs, as all images and metadata arerecorded as numbers, a system fordetermining what those numbers represent – aformat, in other words – is necessary.
In the same way as sentences written using
letters are incomprehensible unless the letterscan be read, sentences are digital expressions
as opposed to painted pictures. Furthermore,in that it is impossible to judge digital signals
instinctively
(they
are
metaphysicalphenomena), they can be explained as what iscalled “emptiness” in Buddhism (Table 3.1).

National Museum of Nature and Science Technology Systematization Survey Report

Vol.10 2008. MarchTable 3.1. Analog and digital
AnalogPhysical Quantity
Vector quantity
Sense
PicturePhysicalEntityDigital
NumeralScalar quantity
Logic
Sentence
Metaphysical
Emptiness

Furthermore, although one gets theimpression that in many cases analog anddigital are used as continuous and discrete,
the concepts of continuous and discrete do
not reflect the true nature of analog anddigital.
While it is possible to treat analog volume
as a continuous physical quantity, it is a factthat digital information must be described as
finite numerical values.
Let us consider a graphical representationof continuous quantity. When converting
continuous quantity displayed in an
analogous form, such as in column 3 of Fig.
3.1, into a graphical form, representative
points, such as in column 1, are selected andthe value of each representative point is
described digitally as a numerical value incolumn 2.
There is the fixed notion that digital isdiscrete, however, whereas, for example,
image sensor cell size is large as comparedwith the size of film molecules anddiscreteness can be ignored with analog, thisbecomes a problem with digital as
discreteness cannot be ignored.
DigitalAnalogFig. 3.1. Graphical representation ofcontinuous quantity.
For example, supposing that a fine probe isplaced on part of a tape on which an analog
signal of shade is recorded, as in Fig. 3.2, andthe shade data for that point is expressed
numerically as a digital signal, it is possible
to constantly change the position of the probe.
From this we can understand that there is norequirement that being sampled, in otherwords discrete, is not an intrinsic prerequisite
for digital, but in a sufficient condition that isin reality required for operation.

Fig. 3.2. Continuous digital conversion.
With digital, as numerical values that areless than the minimum number described are
not displayed, sampling points that are next toeach other seem to be in no particularsequence. This is due to the fact that the
numbers used to describe them are finite, andif it is possible to have non-terminating
descriptions with continuously moving
sampling points, then continuous digital
expressions become a possibility.
The horizontal axis in Fig. 3.2 is not digitaland has a discrete nature, and digital
information is obtained from the vertical axis.
In this way digital must be consideredseparately from discrete.
The meanings of digital and analog should
be understood as explained above andsuperficial interpretations that consider them
to be simply “different methods of expression”
should be avoided.
For example, the definition of one meter
was determined by the General Conferenceon Weights and Measures and although theanalog representation of a meter was the
distance between two points marked on theinternational prototype of the meter managed
by the International Bureau of Weights andMeasures in Paris, it was difficult to maintain
Systematic Survey on Digital Still Cameras

9its immutability due to factors such astemperature, impact and general wear andtear. Therefore, in 1983 it was amended to thedigital expression “the distance traveled bylight in a vacuum in 1/299,792,458th of asecond.”In light of that, the appearance of DSCs,
which, unlike conventional silver halide
cameras that physically record images, record
images and related information logically as
numerically expressed multimedia data, wasan epoch-making event that brought about achange in human thought processes. That is
to say, it caused a paradigm shift in thecamera industry as it negated the view that in
the same way as electronic cameras up untilthat time, DSCs were merely using electronic
technology as a means of recording images
and that they were an alternative means ofrecording images to the photochemical
process.
In reality, by incorporating digitaltechnology into DSCs it was possible torealize new possibilities that were
unthinkable with the electronic cameras that
had been developed up until that time.
In analog electronic cameras that used
floppy disks as recording media, image
processing consisted of handling still images
that had been taken as a physical quantity andthe physical changes that could be made werelimited to things such as transforming,
projecting, trimming and changing the color,gamma and brightness of images as a whole.
However, with DSCs, images consist of
pixels and by handling data from each pixel
numerically it is possible to process data fromeach individual pixel individually. For
example, in single-plate type image sensors
there is what is referred to as de-mosaicing,which
issignalinterpolation
andcompensation for defective cells.

3.1 Characteristics of Digital
Information
Although physical phenomena exist as
analog values, in order to express them as
digital information, which is logical value, itis necessary to convert analog values todigital values using an A/D converter.

10

Fig. 3.3 Sampling during A/D conversion.
The A/D conversion process is identical tothat shown in Fig. 3.1.
When digitizing continuous physicalquantities expressed as y = f(x) as shown in
Fig. 3.3, firstly a representative point (known
as the “sampling point”) is sought and thevalue of each sampling point is expressed as anumerical value, a process that is known as“sampling.”
With sampling, the next sampling point
after the sampling point xi will be xi + 1,
which is a point separated from xi by adistance dx.
When handling analog information,although in reality dx = 0, when handling
digital information, it is necessary to take dx
as a finite value. In other words, thehorizontal axis in Fig. 3.3 becomes discrete.

Aliasing

Spatial frequency

Fig. 3.4. Aliasing.
In Fig. 3.3, the value between the sampling
point xi and the neighboring sampling point xi+ 1, which is shown in gray, is shown as yi at
xi. In other words, the value yi is maintained
between xi and xi + 1. This is referred to as a“hold.”
However, with film, for example, which is

National Museum of Nature and Science Technology Systematization Survey Report

Vol.10 2008. Marchan analog image record, the photosensitive
materials must become discrete on themolecular level and in reality, even withanalog, it is impossible to make dx = 0.
The fact that sampling of signals withproperties f(x) (in this instance the image
input signal) is carried out at a sampling
frequency fs, is equivalent to modulating thecarrier wave frequency fs of an electricalsignal, and as is shown in Fig. 3.4,
frequencies higher than fs become aliasing
distortion as image noise.
With regard to image compression, which
will be mentioned in more detail below, theJPEG used in Exif [1] in most consumer
DSCs uses discrete cosine transform (DCT),
which is a type of Fourier transform, however,as DCT is a value obtained through discrete
sampling, it is a method of frequency analysis
and can be adopted even without the use ofdigital.

3.2 Fourier Transform
Using the integrable function f (x) defined
as 0 ≤ x ≤ 2 π, with an and bn as coefficientsobtained with the following formulae,

This is shown in Fig. 3.5.

Fig. 3.5. Solitary wave Fourier transform.
From this the output signal provided by theaggregation of the solidary waves distributed
over the surface of the image sensor can beconverted to the aggregation of thecontinuous spectrum inside the image sensor,
making it possible to calculate the signal
value at any designated location even if a cell
is not located in such a location.
Furthermore, applying the discrete Fouriertransform gives N real numbers yi (i =0,1,…N-1), to which by applying the discretecosine transformand with the resulting coefficient

the coefficient f (x) can be transformed as a
Fourier series as follows:
can be used to calculate the transform.
More specifically, the real function f (x)will be converted to a function in thefrequency domain as the sum of a harmoniccomponent, which has a basic frequency of 0
≤ x ≤ 2 π.
The output from the cell of an image sensor
can be handled as a solitary wave with awidth equivalent to either the vertical or
horizontal dimensions of the cell.
If the cell dimensions are 2X0 and cell
output is E, then the Fourier transform of thecell output can be derived using the following
formula.

Although this example is a one-dimensionaltransform, an M × N two-dimensionaltransform can be calculated in the same way.
With a two-dimensional transform, the M × N
frequency coefficient can be sought for fromthe DCT using M × N sampling points.
While DCT can be applied to evenfunctions, the coefficient is a real number andcharacteristically energy is concentrated in
low-order coefficients. This characteristic
whereby energy is concentrated in low-orders
produces non-uniform entropy and by using
this property it is possible to compress data
volumes.
Systematic Survey on Digital Still Cameras

11With the JPEGs used in DSCs, after abilaterally symmetrical image has been added
to the image to make an even function, it isconverted to the frequency domain using
DCT calculation. Furthermore, using thepreviously mentioned non-uniform entropy it
is possible to achieve highly efficient data

12

compression.
Note:[1] “Exchangeable Image File Format,”Standard of Japan Electronics andInformation
Technology
Industries
Association CP-3451, 3451-1.

National Museum of Nature and Science Technology Systematization Survey Report

Vol.10 2008. March4 The History of the Camera
4.1 Overview

4.2

It is said that the Greek philosopher
Aristotle, who lived during the 4th century
BC, knew that an outside scene could be
projected inverted onto the wall of a darkroom through a small hole. Applying thisprinciple of the pinhole camera to image
creation, it was the camera obscura, which
was conceived around the 15th century as adevice for copying the image of a subject
onto paper, that was the launching pad for thecreation of a unique camera culture separate
from image culture that was reliant on theskill of the individual to draw pictures.
The camera obscura was a tool forrecording images by tracing by hand an
image projected on paper and which still
depended on the artistic ability of theindividual. As a result of wanting a means ofretaining images without needing to rely on
individual artistic ability or the help of others,
a way of chemically fixing images wasinvented and subsequently led to the age ofthe silver halide camera, which continued formany years.
It was toward the end of the 20th century in1981 when the camera became computerized
and it was immediately prior to the last ten
years of the 20th century that digitaltechnology was introduced and the digital
camera in its present form was born.
Let us now take a look at the history of thecamera up until the advent of the DSC (Fig.
4.1).

Capturing Images

It is said that around 1250, using theprinciple of the pinhole camera, that the
Italian author and architect Leone Battista
Alberti invented the camera obscura. This
enabled even people with no artistic ability torecord images more accurately in a shorter
period of time.
This device was also used by Leonardo daVinci and is the forerunner of the modern
camera.
In the 16th century, as lenses came to be
used in camera obscuras and they were mademore compact, not only were they used bymany French painters when painting portraits,
which were in great demand at the time, butalso by ordinary people as a tool for painting
landscapes.

Fig. 4.2. A camera obscura [1].

Multimegapixels, high performance, RAW
Magnetic Recording Camera
Autofocus
Electronic Shutter
Single Lens Reflex
Twin Lens Reflex
Roll Film
Dry Plate Cameras
Wet Plate Cameras
Negative/Positive Process
Daguerreotype

Fig. 4.1. Camera development.

Fig. 4.3. Camera obscura structure [2].
An external view of a Camera obscura isshown in Fig. 4.2 while its structure is shownin Fig. 4.3. Incidentally, camera means “room”
and “obscura” means “dark” in Latin.
Systematic Survey on Digital Still Cameras

13

In 1725, the German Johan Heinrich
Schultze discovered the light sensitivity ofsilver nitrate, and the English pottery
manufacturer Wedgewood is said to havebeen the first to use the photographic method
to record images using a chemical reaction to
print pictures on pottery.
In 1824, the Frenchman Joseph Niepce
Nicephore announced the development of
heliography. While this used the phenomenon
whereby dried bitumen derived from asphalt
hardens when photosensitized, it required along exposure time of over six hours. “A Man
Leading a Horse [3],” which was taken by
Niepce in 1825 and is said to be the world's
oldest photograph, is shown in Fig. 4.4.

of the Camera.
Although the Daguerreotype was not able
to duplicate photographs, in 1841, theEnglishman William Henry Fox Talbot
invented the negative/positive process which
not only enabled copies to be made, but
greatly reduced exposure time to two to threeminutes. Furthermore, in 1851, Frederick
Scott Archer invented the wet plate
photographic process, which used a liquidcalled collodion (a solution of nitrocellulose
dissolved in a mixture of ethanol anddiethylether) mixed with soluble iodide that
was applied to a glass plate before being
immersed in silver nitrate to create aphotosensitive film, which was then usedwhile wet to take a photograph. This processfurther shortened exposure time to less thanten seconds.

4.3 Cameras as Optical
Instruments

Fig. 4.4. Niepce's “A Man Leading a Horse.”
The first in the world to be sold as a camera
was the Daguerreotype camera, which was
jointly developed by Niepce and compatriot
Louis Jacques Mande Daguerre, andannounced by Daguerre on March 19, 1839
after the death of Niepce. The Daguerreotype
is shown in Fig. 4.5.

In 1871, in place of the wet plate process,the dry plate process was invented whereby
glass plates were coated with silver halide,and in 1888 the US company Eastman Kodak
released a set consisting of a camera and film
made by coating a celluloid film with silver
halide. From that time the film camera
became the predominant type of camera andas it used silver halide it came to be referred
to as the silver halide camera (SH Camera).
In 1928, the German company Franke und
Heidecke GmbH released the twin-lens reflex
camera the Rolleiflex with an image size of
6×6 cm, and in 1950, the world's firstpentaprism-type single-lens reflex camera,
the CONTAX-S, was released by the German
company Zeiss Ikon.

4.4 The Electronization of
CamerasFig. 4.5. Daguerreotype.
This camera required an exposure time of
30 minutes. Incidentally, the anniversary of
the Daguerreotype is celebrated on March 19
each year as the Anniversary of the Invention

14

In terms of the incorporation of electronics
into silver halide cameras, in addition to
flashes,
electronic
exposure
devices,
motorized zooms and motor drives, although
in 1965 the electronic shutter was announced,
followed by autofocus in 1977, despite thefact that many other devices other than thecamera had been made electronic, theNational Museum of Nature and Science Technology Systematization Survey Report

Vol.10 2008. Marchincorporation of electronics into cameras wascomparatively slow as they require aninternal battery.
Up until that time, as silver halide cameras
were optical devices that used the silver
halide chemical reaction, many film andcamera manufacturer technical personnel had
backgrounds in the fields of chemistry or
precision machinery and it could be said thatthe computerization of the camera involving
electrical/electronic technicians was aimed at
the development of technology to supplement
the picture-taking function of cameras.
It was from 1981 that the photographic
method itself made the transition to electronic,
and the DSC in its present form, using digitaltechnology, was developed in Japan in 1988.

4.5

Electronic Cameras

In 1981, Sony's Mavica electronic camera(Fig. 4.6), which was also known as a floppy
camera, was the world’s first electronic
device made in Japan to use a semiconductor
image pickup device referred to as a CCD(Charge Coupled Device) in place of the film
used in silver halide cameras, which in that
respect made it an epoch-making event.

Fig. 4.6. Floppy Mavica.

image quality was on par with that of video
cameras, it was a far cry from that of silver
halide cameras. However, compared withconventional silver halide cameras it had
characteristics such as the following:
1. Instant image replay.
2. Reusable recording media.
3. The ability to transfer images throughtelecommunications.
Furthermore, it did not require a chemical
process and was enthusiastically welcomedby the news media, etc., as a groundbreaking
camerathat
couldrecordimageselectronically.
This electronic camera was the device that
lifted the curtain on the electronic revolutionthat transformed the camera from achemical-based device to an electronic device,
and it could be said that it boasted a numberof advantages ahead of the DSC that was tosubsequently appear.

4.6

Digital Recording of Still
ImagesIn 1980, a research report from Toshiba
regarding the digitization and recording ofstill images onto cassette tape was submitted
to the Magnetic Recording Committee of theInstitute of Electrical and Electronics
Engineers, Inc. (IEEE) of Japan [4], and in1985 the prototype shown in Fig. 4.7 wasannounced by the Institute of Electrical andElectronics Engineers (IEEE) [5].
This device, which recorded a digitized still
image taken with a video camera andrecorded in onto a C-90 cassette tape installed
in a cassette deck, was able to record
approximately 300 still images. The reason
that a C-90 tape was used as the recording
media was because data dropout was minor
when carrying out digital recording due to thethin nature of the base layer. Although this isthought to have probably been the archetypal
digital still camera, it did not lead to any
product sales.

This electronic camera magneticallyrecorded a single frame from a video movie
camera (camcorder), which were alreadypopular at the time, as an analog signal to a2-inch dedicated floppy disk, and although
Systematic Survey on Digital Still Cameras

15

4.7

The Age of the DSC

4-7-1 Background to the Birth of the DSC
In 1992, the Exif standard incorporating theJPEG data compression format came to be
used in almost all consumer DSCs as a
uniform international standard and became
the driving force behind the growth of themarket.

Production Value(100 million JPY)

Fig. 4.7. Cassette camera.

although there was a rapid drop in the numberof silver halide camera produced, overall
camera production has steadily increased
since 1935. Figures 4.9 and 4.10 showmonthly production in terms of units andvalue for silver halide cameras and DSCs
since 1999 when DSC statistics became
available for the first time. According to thesefigures, recently, while DSC monthly
production has been in excess of 5 million
units with a shipment value in excess ofapproximately 100 billion JPY, silver halide
camera monthly production has dropped to
100,000 units with a shipment value of about
500 million JPY [7].

DSCs
Film

Silver halide film cameras
DSCs

Fig. 4.8. Silver halide film camera and DSC
production volume trends [6].
Furthermore, in addition to the dramatic
improvements in image quality andfunctionality that were realized through manytechnological reforms, riding on the wave ofinfrastructuredevelopment(personal
computers/the internet), and the success of
Casio's QV-10 (65,000 JPY) that was
released in 1995 and QV-10A (49,500 JPY)
that was released the following year, themarket for consumer communication devices
rapidly expanded, with DSCs exceeding
silver halide cameras in terms of production
value in 2000 and production units in 2002 todevelop into an industry with an annual
production value in excess of 1 trillion JPY.
Figure 4.8 shows production trends inJapan for silver halide cameras and DSCs
since 1935 in terms of the number of units
produced. Since the development of DSCs,

16

Production(1 million units)

Fig. 4.9. DSC/silver halide film camera
production value trends.

DSCs
Film

Fig. 4.10. DSC/silver halide film camera
production trends.
4-7-2 The Path to Electronization
Although some are of the opinion that theadvent of DSCs can be attributed to measures
to deal with the depletion of the silver
resources that are essential for silver halide
cameras and environmental problems, wasthat really the case?
Certainly during the period between thelatter half of the 1970s to the first half of the
1980s measures to deal with resource
depletion and control pollution were a major
issue in society. Due to these concerns

National Museum of Nature and Science Technology Systematization Survey Report

Vol.10 2008. Marchregarding the depletion of resources, the priceof silver continued to soar and the US
National Association of Photographic
Manufacturers (NAPM) [8] lobbied thegovernment to abolish one USD coins using
silver, while in Japan, although the silver in
100 JPY coins had already been replaced withnickel silver, the price of old 100 JPY coinsmade of silver had already exceeded 100 JPY
on account of the value of the silver.
The film and photographic paper used withsilver halide cameras used silver andchemicals were used during the developing
process.
However, at the time when DSCs weredeveloped at the end of the 1980s, these
problems had already been solved.
That is to say, the price of silver hadstabilized due to forecasts of long-term stablesupply and the adoption of silver recovery
processes. With monochrome (black andwhite photographs), as silver remains in film
and on prints, minute volumes of silver are, infact, consumed. Nevertheless, with color
photography, only dye called a couplerbonded with silver particles and remained on
film and prints and silver was completely
recovered during the developing process.
Furthermore, strict antipollution laws wereenacted with regard to the use of chemicals
by shops developing, printing and enlarging
photographs, thus completely solving suchenvironmental pollution problems. In thisway, in the silver halide camera industry,
which is in reality a chemical industry,measures regarding resource depletion andenvironmental conservation had already been
introduced and the problems faced by silver
halide photography had already been solved.
However, the sense of uncertainty
regarding resources and demands forenvironmental conservation were generalsocial phenomena and the industry-wide trend
to move from chemical-based technology toelectronics-based technology – which could
be referred to as the second industrial
revolution – had already reared its head andwas gaining traction. In the midst of thistechnological revolution, there were moves tointroduce technological reform into thephotographic industry. As the technologicalenvironment was ripe for change, thesemoves resulted in a time of catastrophic
change within the photographic industry fromwhich a new industrial model emerged.
Fuji Photo Film (now Fujifilm), the top
film manufacturer in Japan, was not only afilm manufacturer, but also sold cameras andsingle-use cameras (QuickSnap) as part of its
imaging business and in 1966 the 8 mm film
movie camera Fujica Single 8 sold in huge
numbers after the airing of the “I can shootmovies, too” commercial.
However, as using the Fuji Single 8 was
expensive due to film and processing costs, it
quickly lost its place to the 8 mm video
camera when it was announced in 1985.
This “replacement drama” was due tofactors such as the instant nature, ease of
playback, and the low cost of the reusable
recording media used in the 8 mm video
camera, which used electronic technology.
Fujifilm currently has a nationwide service
system for printing images taken with DSCs
and the photographs obtained through thisservice use the same chemical reaction as
used in silver halide photographic prints.
In this way we can see that although thechemical industry still emphasizes quality andmass processing capacity in its commercial
business, consumers have welcomed theadvantages of electronics in consumer
products.
Furthermore, in terms of the camera's
relationship with the news media, as they
were in need of a means to send photographs
instantly rather than having to develop andprint them before wiring them, by the time of
the Los Angeles Olympics the media had
already enthusiastically embraced the use ofelectronic cameras. In this way, even in theworld of photographs, the transition fromchemicals to electronics continued as theindustry was swept along by the inevitableflow of technology.
Electronics is the field in which electricalmanufacturers perform the best and they have
many specialist technicians. However, in thelatter half of the 1980s, there were companies
among the camera manufacturers and film
manufacturers, which had been built on thefoundation of precision machinery andchemistry, that strengthened their electronics
capabilities with the aim of further expanding
Systematic Survey on Digital Still Cameras

17their technological capabilities and productrange by following the trend of using
electronics in cameras and they started work
on DSCs.
During the same period, nonvolatilememory that was rewritable electronicallywas developed at Toshiba and they had been
searching for applications that used memory
cards using that technology. Furthermore,they had been making progress on technology
for digitally recording still images and theperformance of semiconductor devices that
supported that technology, such as seen in thepreviously mentioned Toshiba audio cassettetape still image recording device.
Up until that time, the A/D (Analog to
Digital) converter that digitized the images
did not have adequate performance to be able
todigitizeimages
in
real
time,
high-efficiency compression technology with
only low levels of degradation had yet to be
developed, and there was no way to store
digitized images other than SRAM (Static
Random Access Memory), which required
backup power to store them in semiconductor
memory. Therefore, even though it wastheoretically possible to propose a DSC, therealization of the concept was considered tostill be some time away.
Nevertheless, memory was developed using
a new principle that overcame the limitationsof the recording media that existed at thetime.
4-7-3 Early DSCs
In addition to functioning as a camera thatrecords images, as we will see, a DSC is animage information device that simultaneously
records various information associated withimages that are taken.
In 1988, Fujifilm announced the world's
first fully digital camera, the DS-1P (Fig.
4.11), which recorded an image acquired
using a CCD as a digital signal on a memory
card jointly developed with Toshiba, and in
December of the following year, they
released the world's first digital camera(Fujifilm: DS-X; Toshiba: IMC-100) (Fig.
4.12) with the aim of carrying out the world's
first DSC market survey.
In November 1990, the MC-200, which
was the world's first commercially produced

18

DSC, was released by Toshiba.

Fig. 4.11. DS-1P.

Fig. 4.12. DS-X (IMC-100)
These early DSCs, which captured a single
frame (or a single field) in the same way as
an electronic camera or a video movie camera(camcorder), compressed it as a digitizedimage signal and recorded it tosemiconductor memory, and as the aim wasto replay these images on a TV in the same
way as an electronic camera or camcorder,
they had about the same number of pixels(350,000) as displays using the Video
Graphics Array (VGA) standard.
As it is necessary for cameras taking still
images to be able to handle taking them on a
vertical or horizontal angle, although it isdesirable for the image sensor to have asquare pixel aspect, as production lots are
small and special development of image
sensors costs a huge amount of money, inthese early DSCs a single 2/3-inch 400,000
pixel FIT (Frame Interline transfer) CCD
with a non-square pixel aspect ratio for use ina movie camera was used and image
processing was used to create square pixel
data.
Moreover, as at the time there was no
appropriate form of data compression
technology, sub-sampling was used for 2D
compression and ADPCM (Adaptive
Differential Pulse Code Modulation) wasused for signal compression and 6 or 12
images were recorded to 9 Mbit (1.125MB)
or 18 Mbit (2.25MB) SRAM memory cards

National Museum of Nature and Science Technology Systematization Survey Report

Vol.10 2008. Marchrespectively that were backed up by battery.
In terms of image processing circuits, as thenumber required was too small to develop a
dedicated Large Scale Integration (LSI) for
mass production and custom-order parts wereused, the beta unit for market survey purposes
was not only not up to standard in terms of
performance, but the price was expensive at
1.6 million JPY as it included peripherals,
such as a playback device, a DAT recorderand modem.
Therefore, as image quality was nowhere
near as good as that of silver halide cameras
and the high price of early DSCs meant that it
was utterly impossible to even consider
putting on the shelves in stores for sale to thegeneral public as a consumer camera, there
was no option other than to try and findcustomers who valued the features not foundin silver halide cameras; namely their instantnature and the ability to transfer images.
One of the major customers at that time
was an airline who used DSCs at theirmaintenance facility in Hokkaido. Whereas
previously they had wired photos from theirmaintenance facility in Haneda in order toverify areas for repair, using DSCs they wereable to transfer the information over atelephone line and so that repairs could bechecked by both parties. In addition,customers who had previously usedconventionalwire
photos,includingnationwide auction networks, etc., werelimited to certain applications and other R&D
divisions within the same industry who werecarrying out their own DSC development,
meaning that DSCs were never madeavailable to the general public.
As the technological level of early DSCs atthat time could not rank with that of silver
halide cameras in terms of quality or price,
they lacked the ability to develop a consumer
market.
However, in addition to the fact thatelectronic cameras had revolutionized theindustry by taking the camera out of thechemical industry and into the electronics
industry by rendering images electronically,
DSCs had advantages such as the following
over electronic cameras:
1. By changing the recording format fromanalog to digital, they eliminated thedegradation of images transferred or
copied.
2. By recording images electronically tosemiconductor memory rather thanmagnetically to floppy disks, the drive
section of recording media was eliminatedand recording and reading times wereshortened.
However, with early DSCs, even thoughimages were able to be imported into personal
computers (PCs), as image processing
softwarefunctionswere
inadequate,
compatibility with PCs due to the use ofdigital signals was a feature that was not that
remarkable.
Furthermore, as the internet had yet to be
developed throughout the country, eventhough images taken on a DSC could be
imported into a PC, it was not possible tosend and receive them over the internet,
which is almost second-nature to us now, butrather images were sent and received at thattime on the VGA level via TV telephone or
shared through direct PC to PC
communication.
4-7-4 From Viewing on TVs to Viewing
on PCsWith image quality designed for replaying
images on a TV screen, even if images are
printed out they are coarse and scanning lines
are visible, and in terms of image quality, it is
not even as good as disposable silver halide
cameras.
Moreover, as the price of DSCs was inexcess of several hundred thousand yen, atthat time, it was impossible to predict thatthey would ever replace silver halide cameras
as consumer cameras as they have, in fact,
done now.
Although Apple released a consumer DSC,
the Quick Take 100, in 1994, it failed to catchon.

Systematic Survey on Digital Still Cameras

19images for use on websites and images taken
on DSCs being shared over the internet, thishad a major impact on the growth of the DSC
market (Fig. 4.14).
Based on statistics from the Ministry of Internal Affairs and Communications.

Fig. 4.13. PC ownership [9].

20Fig. 4.14. Internet utilization trends [10].
(1 billion JPY)

ICT investment as a proportion of private
sector capital investment

17.1 trillion JPY

Private Sector ICT Investment

At the time, the segment of the market thatwas buying DSCs was mainly the media, whoprized the instantaneous nature of thetechnology and ease of transmitting images,
and in light of this, in 1995 Fujifilm released
the DS-505 (1.4MP), Nikon released the E2S(1.4MP), Canon released the EOS-DCS3(1.3MP), Minolta (now Konica-Minolta)
released the RD-175 (1.75MP), all of whichwere professional DSCs.
Nevertheless, although the household PC
ownership rate (excluding single parent
households) around 1993 was around 10%,from around that time it started to increase(Fig. 4.13).
If the main purpose is to import images intoa PC, then as long as they are compatible
with the image sensor, image limitations are
eliminated and DSC specifications, such as
the number of pixels, image size and aspectratio, can be freely selected and it is possible
to easily create photographs at home using aprinter connected to a PC.
In this way, by changing the aim of the
DSC from replaying images on a TV to
inputting them into a computer, it could besaid that the road into the future was opened
up for DSCs as a consumer device, and thefact that it was Casio that led the way
probably means that it needed a company thatwas not tied to TV or video technology tocome up with that idea.
The household PC ownership rate rose toaround 15% in 1994, exceeded 20% in 1997
and from around 1999 rapidly increased tothe extent that today it is in excess of 70%.
Moreover, internet access was madeavailable in Japan from 1994 and with DSCs
being recommended as tools for creating

Showa

Telecommunications
equipment(Year)

平成元

Computers/auxiliary equipment

Software

ICT investment as a proportion of private sector capital
investment

Fig. 4.15. Real ICT investment trends [11].
Capital investment in ICT, including theinternet, has rapidly increased since 1995
(Fig. 4.15).
It could be said that by skillfully riding the
ICT wave that sales of DSCs rapidly
increased.
4-7-5 The Advent of Consumer DSCs
The fact that the aim of DSCs was changed
from playing images back on a TV toimporting them into a PC was a major turning
point for DSCs. However, at a time when thehousehold PC ownership was less than 20%,
it was impossible to create a market for
consumer DSCs purely from households with
PCs and first it was necessary to reduce theprice and arouse the curiosity of that sectionof the consumer market that liked “newthings.” At Casio, an unofficial project by asmall group of researchers was working todevelop a low-cost DSC.
Although the first units developed were
given the nicknames “Omoko” (“heavy
child”) and “Atsuko” (“hot child”) (Fig. 4.16)
as the former was an extremely heavy
prototype and the latter was a prototype thatgot very hot due to high power consumption,
ultimately the specifications for a consumer

National Museum of Nature and Science Technology Systematization Survey Report

Vol.10 2008. Marchunit were finalized and in 1995 the QV-10(Fig. 4.17) was released at a price of 65,000
JPY.
Moreover, the following year, the QV-10A,
which had basically the same functions, wasreleased at a price of 49,800 JPY. As up untilthat time there had never been a DSC priced
under 100,000 JPY, the release of thesemodels at this price point had a major impact
on the camera manufacturers.

Fig. 4.16. Casio's DSC prototype “Atsuko.”

Fig. 4.17. Casio's QV-10.
However, the QV-10 and QV-10A only had
250,000 pixels and as the image quality of thededicated printer was poor, it could be said
that almost none of the camera manufacturers
expected that the DSC would displace thecamera and that it would become an image
data device that would go even beyond thesilver halide camera. Therefore, the DSC
R&D
departmentsofthecameramanufacturers were mostly full of electronics
technicians, in many cases what they were
doing was away from the mainstream, andfew camera specialists developing optics, etc.,
were involved.
The QV-10 and QV-10A used the Exif
standard, which we will examine in moredetail below, that had already been adopted as

the standard for DSCs in Japan and which
had been proposed as an international
standard.
Exif, which incorporated the JPEG image
compression format that was cutting-edge
technology at the time and which was aninternational standard developed in Japan,
was adopted by all DSC manufacturers. As
all products therefore shared the same
specifications, consumer desire to buy was
not dampened, which made it possible toachieve higher household penetration, leading
to rapid market growth.
In addition to the above, as consumer
appliance manufacturers, who were experts incomputer technology, entered the market thatwas previously the domain of the optical
instrument manufacturers, the shape of thecamera industry, including manufacturing andmarketing structure, was radically changed
with the appearance of DSCs.
The performance of DSCs being sold atpresent surpasses that of silver halide cameras
and they are being sold at a somewhat
cheaper price than equivalent silver halide
cameras.
4-7-6 Digital Single Lens Reflex Cameras(DSLRs)Cameras can be classified into four
different categories according the type offinder they use for verifying the subject prior
to taking the photograph:(1) Viewfinder Cameras
In addition to the lens used for taking
the photograph, these cameras have aninspection window through which thesubject can be verified. As they arecheap, many compact cameras are of thistype.
(2) Single Lens Reflex Cameras (SLRs)
The image of the subject as seen
through the lens used for taking thephotograph is reflected by a mirror onto
a focusing screen so that the subject canbe verified. Only at the moment when
the shutter is released does the mirror
move out of the way to expose thephotosensitive surface (film or an image
sensor). Many high-end cameras use thistype and many feature interchangeable
lenses.
Systematic Survey on Digital Still Cameras

21

(3) Twin-Lens Reflex Cameras
In addition to the lens used for taking
the photograph, this type of camera has
another lens coupled with that lensthrough which the subject can be viewed.
Although the subject can be viewed
when the shutter is pressed, there is the
disadvantage of parallax.
（4）View Cameras
A focusing screen is placed on theimaging surface and after verifying the
subject sheet film or a dry plate, etc., isinserted in its place and the photographtaken. This type of camera is often usedin places such as studios.
Although the structure of an SLR iscomplicated, as we can see from Fig. 4.18, as
it is possible to verify exactly the same image
as that projected onto the photosensitive
surface, this type of viewfinder is used inhigh-end cameras.
Pentaprism

ApertureFilm
MirrorShutterFig. 4.18. SLR structure.
The first SLR is said to have been the
Ihagee Kine-Exakta, which was released in
1884.
However, the first SLR welcomed by themarket was the CONTAX S, which was
released in May 1949. In Japan, Asahi
Optical (now Pentax) released the Asahiflex
in 1952.
With DSCs, from the time that the first
DSCs appeared, although SLR-type DSCs
started to appear in media-related fields, they
did not really catch on.
It was Nikon's D1, which was released in
1999 at a price of 650,000 JPY, and Canon’s
EOS-D30, which used an APS-size image
sensor and was released the following year ata price of 358,000 JPY, that really launched
the digital SLR (D-SLR). Since the D30, thefocal length of interchangeable lens-type
D-SLRs has gained popularity as being “3522mm equivalent.”
With DSCs, as the sensor signal isdisplayed on a monitor screen, such as a
Liquid Crystal Display (LCD), this makes it
possible to verify the picture being taken in
the finder just as it really is.
With regard to the aim of making it
possible to change lenses and verify the
picture using a more detailed image, this too
has been achieved and sales of D-SLRs are
growing, with models for the commercial,professional and high-end amateur markets.
D-SLRs have now become mainstream andoffer not only higher quality images, but also
the traditional advantages of an SLR, such as
interchangeable lenses and the ability toverify the picture using a more detailed
image.
While general consumer DSC image data is
8-bit and this is output with JPEG
compression using the sRGB color space,which is the same color reproduction range asthat used in TV monitors, as most SLRs
striving for high image quality can extract
raw data which is almost identical to the
output signal from the sensor, this allows theuse of a greater bit-depth and a color spacethat is much wider than sRGB.
However, as raw data is output in a format
specific to the image sensor, there is the
disadvantage that proprietary software uniqueto each camera is required in order to obtain(develop) an image.
Consumer DSC image files are recorded inaccordance with the unified Exif standard andas it is possible to process files in a standard
manner in accordance with DCF (design rulefor camera file system) [12], in light of thefact that it is possible to process images in acommon way regardless of the type of camera,
although there were moves to standardize raw
data under an ISO standard, as there is thepossibility that it may lead to the disclosureof the know-how of each company, DSC
manufacturers were loathe to do so.
4-7-7 Camera Phones (CP)The first mobile phone to be equipped witha camera function was manufactured in 1999
by Kyosera and sold by DDI Pocket (now
WILCOM) as the VP-210. Although this wasa PHS phone with a 110,000-pixel

National Museum of Nature and Science Technology Systematization Survey Report

Vol.10 2008. MarchComplementary Metal Oxide Silicon(CMOS) sensor, both the camera and the
LCD screen were on the same side as it was
designed for use as a videophone. In addition
to this, although TUKA and NTT DOCOMO
released a trial model to which a camera
function could be added by means of an
adaptor, it did not catch on.
The first real commercial CP was the
J-SH04 that was jointly developed by
J-Phone (now SoftBank Mobile) and Sharpand brought to market in November 2000.
The ability to send images by mail was
welcomed by the market and J-Phone quickly
gained market share.
After that, the various carriers followed,
with Tuka and Sanyo releasing the TS11 in
2001, joined the following year by au andCasio with the A3012CA and NTT and Sharpwith the SH251i.
Early CPs had few pixels and although theimage taken could be replayed on the screenof the phone, from 2003 the various
companies introduced models with more than
1MP (megapixel), followed in December ofthe same year by models from NTT
DOCOMO, Vodafone and au with 2MP.
Models with 4MP arrived in 2005 and now
there are even models with 5MP, which isabout the same as that of general DSCs.
Mobile phone production trends are shownin Fig. 4.19.
100 million JPY

Foreign Demand
Domestic Demand

FY

Fig. 4.19. Mobile phone production trends[13].
In terms of the technological conceptbehind CPs, they were developed under the
direction of the terminal manufacturers and asthese manufacturers were also DSC
manufacturers,
DSC
technology
wastransferred to CPs. Therefore, Exif, which
was used in DSCs, was adopted as the image

file format for CPs, meaning that image files
could be exchanged between CPs and thatimages taken on a CP were compatible when
saved to a PC.
Considered only in terms of the number ofpixels, CPs compare favorably with DSCs
and although they have other camera features,such as zoom functions, they are by naturesmall, mobile handsets for communication
purposes that as an auxiliary feature have acamera and in terms of lens and image quality,
at present they do not measure up to thecapabilities of dedicated DSCs – and even if
CP camera performance increases, DSC
performance is most likely to already be one
step ahead. However, they are mobile andconvenient, the images taken can betransferred and saved, and CPs with basic
picture-taking capabilities mean that it is notnecessary to carry a camera in addition to amobile phone, they are ideal for snapshots
and in 2003 they outstripped sales of mobile
phones with no camera function to become
mainstream.
While there are legal restrictions regarding
providing DSCs with communication
functions, CPs are positioned as a new
consumer data communications device, themainfunction
of
which
is
telecommunications. By providing mobile
phones with a camera function, if the purpose
is just snapshots and there is no real emphasis
on image quality, then it could be said that
there is no real necessity to carry a DSC in
addition to a mobile phone.
Therefore, it is thought that a major newmarket for CPs as snapshot cameras will becreated in addition to the high-end camera
and compact camera markets.
Notes:[1] Image provided by the Japan Camera
and optical instruments Inspection andtesting Institute (JCII) Camera Museum.
[2] Saturday Magazine, 1838 (Issue No.
unknown).
[3] Although it was previously thought that
“View from the Window at Le Gras”
taken by Niepce in 1826 was the oldest
photograph, “A Man Leading a Horse”
was discovered early this century and is
now said to be the oldest.
Systematic Survey on Digital Still Cameras

23[4] Kageyama et al., “Digital Still Image
Recording Device using a Cassette Deck,”
Magnetic Recording Committee of theIEEE Japan, MR80-25, October, 1980.
[5] S. Kageyama, K. Kudo, M. Tanaka, M.
Ohyama and M. Ohkawa, “Digital Still
Picture Recorder utilizing an Ordinary
Audio
Cassette
Deck,”IEEE
Transactions on Consumer Electronics,
Vol. CE-31, No. 2, pp.96–107, May
1995.
[6] Created based on statistics from the
CameraandImaging
Products
Association (CIPA) and statistics fromthe JCII Camera Museum.
[7] Created based on statistics from the
CameraandImaging
Products
Association (CIPA).
[8] TheNational
Associationof
Photographic Manufacturers (NAPM)
was created in 1946, changed its name in1997 to the Photographic and Imaging
Manufacturers Association (PIMA), andmerged with the DIG (Digital Imaging
Group) to become the International

24

Imaging Industry Association (I3A) in
2001.
[9] Ministry of Public Management, Home
Affairs, Posts and Telecommunications,
Telecommunication Usage Trend Survey
Results (Consumer Edition), 2001
Edition, p.1.
[10] Ministry of Internal Affairs andCommunications,
Information
andCommunications in Japan, 2007 Edition
p.151.
[11] Ministry of Internal Affairs andCommunications,
Information
andCommunications in Japan, 2007 Edition,
p.12.
[12] “Design Rules for Camera File Systems,
DCF 2.0” in Japan Electronics andInformation
Technology
Industries
Association(JEITA)
Standard,
September 2003.
[13] “Forecast of Industrial Electronic
Equipment Demand,” Japan Electronics
and Information Technology Industries
Association(JEITA),p.
16,
FY2006−2009.

National Museum of Nature and Science Technology Systematization Survey Report

Vol.10 2008. March

5 DSC Structure
According to ISO12231 (Vocabulary), a
DSC is defined as a “portable, hand-helddevice which incorporates an image sensor
and which produces a digital signal
representing a still picture,” with a note
stating, “The digital signal is typicallyrecorded on removable memory, such as asolid-state memory card or magnetic disk.”
Aperture

Shutter
External
Devices

Electronics

OpticsAnalogProcessing
Section

DigitalProcessing
SectionImage Sensor

Memory Card

Optical LPF

Power Supply

Display

Fig. 5.1 DSC structure.
In other words, an image sensor is essential
for a DSC, which is a mobile image data
device where the light from the subject forms
an image on the flat surface of the image
sensor with its rows of photoelectrictransducer cells, and the electrical output
from each cell is extracted and converted todigitalandgenerally
recordedon
semiconductor memory or magnetic disk asimage data.
The basic structure of a DSC is shown in
Fig. 5.1. Overall, it is divided into an image
sensor (which converts light into electricalsignals), and optics, electronics, storage(memory card), display (LCD, etc.) andpower supply (battery, etc.) systems.
The optics system consists of a lens, shutter,
iris, optical low-pass filter (LPF) and an
IR-cut filter, etc. In compact DSCs, exposure
time is adjusted electronically and some units
do not have a mechanical shutter.
The electronics system consists of ananalog signal processor, digital signal
processor, controller, and output andrecording sections. The main constituent
elements of DSCs are described in moredetail below.

5.1

Image Sensors

The image pickup devices (image sensors)
used in DSCs can basically be categorized
into two types – CCD and CMOS sensors –depending on how the signal is read fromeach cell and how that signal is amplified.
With
both
types,
extremely
small
photoelectric transducers (photodiodes) only
a few microns in size that use the internal
photoelectric effect of semiconductors(silicon) are arranged in a regular
two-dimensional pattern.
Light

Conduction Band

Photoexcitation

Valence BandP Layer

Depletion Layer

N LayerFig. 5.2. P-N junction photodiode band
structure.
The state when reverse bias is applied to
the P-N junction of a semiconductor made ofsilicon, etc., is shown as an energy band
structure in Fig. 5.2. When light from outside
illuminates this junction, excitation of theelectrons in the valence band occurs on the
conduction band in the depletion layer,
leaving a positive hole in the valence band.
These electrons and positive holes are
attracted to the impressed electrodes to
produce current in proportion to the strength(intensity) of the light over a wide
illumination range. This is the principle of thephotodiode and each cell of the image sensor
extracts output from a photodiode.

Systematic Survey on Digital Still Cameras

25

Photodiode
Color Filter

Transfer
Circuit

Amplifierapart on the subject.

Fig. 5.3. CCD and CMOS sensors.
The typical structure of commonly used
Interline Transfer CCD (IT-CCD) and CMOS
image sensors is shown in Fig. 5.3.
In IT-CCD sensors, cells are formed in agrid pattern on the circuit board and thecharge produced in each cell according to theintensity of the light is transferred
simultaneously to the charge transfer register(bucket) of each cell. The contents of eachbucket are then transferred out in a verticaldirection in turn from the cell above to thecell below, and at the bottom the contents arethen transferred out in a horizontal direction
to the right. This differs from a CMOS sensor
in the sense that the contents of each cell areread out using an address line.
Moreover, with a CCD, in the final stage ofthe bucket relay, a single amplifier amplifies
the signal, while with a CMOS sensor there isan amplifier for each cell.

Fig. 5.4. Subject and image sensor.
A model of the relationship between thesubject and the image sensor is shown in Fig.
5.4. As cells are the smallest units of theimage sensor, the data of incoming lightwithin a solid angle entering each cell is dealt
with as an average value for the data within
the solid angle and it is impossible to further
divide up the data of the subject seen throughthe lens within the solid angle into smallerparts. Therefore, when light emitted from two
points that are extremely close together on thesubject enter into the same cell, it is
impossible to distinguish those two points

26

Fig. 5.5. Schematic depiction of a cell.
That is to say, the subject is recorded as amosaic-like image corresponding with thecell pattern for the subject. Generally, thehigher the number of pixels, the smaller thesolid angle of each cell is expected to be, andthe more detailed the mosaic pattern becomes.
Therefore, each cell must correspond to an
adequately small part of the subject.
When considering image sensors with asquare cell structure arranged in a grid pattern
on a substrate such as shown in Fig. 5.5, asingle direction on the image sensor
corresponds to the horizontal axis x in Fig.
3.3.
In other words, images captured by theimage sensor are spatially discrete, and theoutput signal from each cell is derived as adigital value through later processing.
The total number of cells on an image
sensor is referred to as the gross sensor
resolution. However, not all cells are used toform an image, and the cells on the image
sensor that are used to form an image are
known as effective pixels. The number ofeffective pixels on the image sensor isreferred to as the effective sensor resolution.
In Fig. 5.6, an image on an image sensor isshown. The central grid area is the output
image, while the cells in the surrounding grayarea are cells called ring pixels that are used
for image processing purposes, such as
sharpening and pixel interpolation.

National Museum of Nature and Science Technology Systematization Survey Report

Vol.10 2008. MarchFig. 5.6. The concept of ring pixels.
Although cell data from this area will not
be displayed as an actual image, such data
plays an effective role in improving image
quality, and ring pixels are permitted to be
included when describing the effective sensor
resolution.
The definition of resolution is a physicalquantity that expresses the spatial frequency
response characteristics of a subject, and inorder to measure this, a chart with continuouschanges in spatial frequency, such as thatshown in Fig. 5.7, is photographed to show towhat degree spatial frequencies can be
reproduced, or patterns with changes in black
and white graduations, such as shown in Fig.
5.8, are photographed and the spatial
frequency response (SFR) is sought bycarrying out Fourier analysis of the output
signals.

Fig. 5.7. An example of a resolution
measurement chart.

Fig. 5.8. An example of an SFR measurement
pattern.
In addition to these, various methods ofmeasuring resolution and charts and software
for calculating resolution are proposed anddiscussed in ISO TC42. The chart shown in
Fig. 5.9 is a resolution measurement chart
proposed by Japan (ISO 12233 chart).

Fig. 5.9. An ISO12232 resolution chart.
In many cases it is mistakenly thought that
DSC resolution is primarily determined on
the basis of the number of pixels. Although it
is true that the number of pixels is a factor in
determining resolution, resolution is also
governed by factors other than the number ofpixels, such as image processing methods,
filter structure and optical performance, anddepending on whether image quality is set tofine or normal when shooting, etc.
It is difficult to seek a numerical value toeffectively compare the number of pixels on a
DSC with film as the grains of photosensitive
substances are not arranged in a regularmanner and depending on sensitivity the sizeof such grains varies. It is possible, however,to estimate such a value by measuring spatial
frequency characteristics using ISO charts,
etc. It is therefore said that ISO100 film is theequivalent of 6MP to 10MP, while ISO400
film is the equivalent of 4.5MP to 10MP.
Therefore, strictly in terms of the numberof pixels, it could be said that recent DSCs
are on par with or superior to film cameras.
As they are, the cells on CCD and CMOS
sensors react to the intensity of light and aresimilar in that respect to monochrome film.
Therefore, in order for them to respond tocolor, it is necessary for each cell to have acolor filter. On single-plate image sensors,
the color filter on each cell is arranged in a
mosaic pattern, while three-plate image
sensors use prisms, etc., to direct incoming
light from the subject through color filtersand onto the three image sensors.

Systematic Survey on Digital Still Cameras

27

5.2

Fig. 5.10. Bayer primary color filter.
In terms of color filters, there are primarycolor types, which pass light through thethree primary colors (red, green and blue),and complementary color types, which pass
light through cyan, magenta and yellow
filters.
An example of the primary color filter type
(Bayer type) is shown in Fig. 5.10. Therereason that there are twice as many green
filters as there are red or blue is that thehuman eye is more sensitive to green than it
is to red or blue, and increasing the number ofgreen filters has the effect of increasing visual
resolution.
Each cell on an image sensor is called apixel (pixel = picture element) and thenumber of effective pixels on a DSC image
sensor is described in terms of megapixels,
for example 3MP.
On the other hand, pixel is also used torefer to the smallest constituent element of animage after carrying out image processing,such as the compression of image sensor
output and image correction.
Although the former is a concept for
expressing the smallest physical constituent
element on the image sensor that captures
images and is specific to each image sensor,
the latter is a concept describing the smallest
constituent element of an output image,something that changes due to processing,such as image compression.
In this document we will refer to thesmallest constituent element of an image
sensor on the input side as a cell, whilereferring to the smallest constituent elementon the output image as a pixel.
The number of cells per millimeter is
described as the spatial frequency of theimage sensor.

28

Optics

Optical technologies, such as lens design
and flare countermeasures, have beendeveloped over many years by silver halide
camera manufacturers, and for camera
manufacturers who have established theirown know-how in silver halide cameras, thisis one of the areas where they candemonstrate their expertise the most.
However, in order to design an optimum
lens system it is necessary to consider image
sensordimensions
andphysicalcharacteristics.
As we can see in Fig. 5.11, the size of thephotosensitive surface of 35 mm film is
36×24 mm and it has a diagonal measurementof approximately 43.3 mm. By contrast, while
in some DSCs the size of the image sensor isthe same as that of the photosensitive surfaceof 35 mm film, it is usually smaller and for
D-SLRs is about 24×16 mm (diagonalmeasurement of 28.8 mm), while the 2/3 typeimage sensors used in many fixed-lens DSCs
is 8.8×6.6 mm (diagonal measurement of 11mm) and the 1/3 type is 4.8×3.6 mm (6 mm
diagonally).

Fig. 5.11. Image sensor size and focal length.
If the size of the image sensor is small, thenthe photographable range of the subject(angle of view) is also small, and when theimages taken are played black at the same
size as they were taken, then images with asmall angle of view look like they were takenwith a telephoto lens. In other words, if a 35
mm lens for use with 35 mm film is used on a
DSC with an image sensor where thediagonal length of the image sensor is D(mm), then the apparent focal length of thelens can be obtained using the following
formula:National Museum of Nature and Science Technology Systematization Survey Report

Vol.10 2008. MarchTherefore, when using a 35 mm film lenson an interchangeable lens-type DSLR, thefocal length will be shifted to the telephotorange. So, for users who are used to the 35
mm film focal length, the focal length in theabove equation is displayed as 35 mm.
On the photosensitive surface of the image
sensor, for images with a higher frequency
than the previously mentioned spatial
frequency, or in other words, for images thatare finer than the size of the cells, image data
for more than one image will be input into asingle cell. As a result, images with a spatial
frequency that is higher than that of the cell
spatial frequency will not only playback
badly, but artifacts will be produced. In orderto prevent this, an optical low pass filter(OLPF) is required to block image signals
with a spatial frequency that is higher than
the spatial frequency of the cells by using
crystal birefringence, etc.
Although it is easy to emphasize electronic
technology when talking about devices usingnovel digital technologies, in terms of themain focus of development, the optical design
capabilities inherited from the silver halideera are essential for enhancing the optical
performance of DSCs.

5.3

Electronics

The output from the image sensor itself isan analog signal. After passing through a
Correlated Double Sampling (CDS) circuit toreduce image sensor noise, this output signal
is converted by the A/D converter into a
digital signal. The digital signal in consumer
DSCs is 8-bit (256 colors).
Output data from this A/D converter thathas only been processed for data linearity,
dark current reduction, shading andsensitivity correction, flare removal and whitebalance is referred to as raw data.
In digital image processing, after cell defectand variation correction, de-mosaicing(mentioned later) and sharpness correction
have been carried out, in consumer DSCs theimage file and metadata are then created inaccordance with the Exif image file format.

5.4

RecordingIn most consumer DSCs, memory cards
containing semiconductor memory are used
as recording media.
Although PC cards containing SRAM wereused in early DSCs, a backup battery was
required inside the card and memory size wassmall.
Since the release of flash memory in 1984,
various companies have released newmemory cards, such as CompactFlash, which
was released by SanDisk in 1994,
SmartMedia [4], which was released by
Toshiba in 1995, MMC [5], which was
released by Siemens and SanDisk in 1997,
and Memory Sticks, which were released bySony and SanDisk in 1998.
Not only do these cards come in various
shapes and sizes according to their intended
applications, they use various memory
control and data transfer methods and canhave various other features, such as security.
However, the image files recorded in thesecards all comply with the Exif standard,regardless of what kind of memory card they
may be contained in, and the directory
structures within the cards are all based on
DCF.
Therefore, when using PC-compatible
memory cards, it is possible for image files tobe read from and written to memory cards,
regardless of the type of card.
The creation of an image format
independent of recording media type was oneof the major features of DSCs and preempted
the kind of format wars seen with video
between the VHS and Betamax formats that
only served to confuse the market. This also
resulted in fair competition for all DSCs andwithout a doubt contributed to the rapid
growth of the market.

5.5

Displays

Another feature of DSCs is that the image
taken can be verified on the spot and thephotograph taken again if necessary. The first
consumer DSC model equipped with an LCD
was the Casio QV-10.
When using a film camera, the fixedshooting style is to hold the camera up to the
Systematic Survey on Digital Still Cameras

29face and look through the viewfinder with
one eye. However, with DSCs, despite thefact that most DSCs have an optical
viewfinder, in many cases the shooting styleused is to hold the camera away from the faceby extending the arms to a certain degree inorder to see the LCD screen. In terms of
preventing camera-shake, although it may be
preferable to hold the camera up to the face,being able to verify images while shooting
seems to be the preferred option in terms ofshooting style.
Under the DCF file handling specification30

used by DSCs, devices for replaying images
are called Readers, with devices equippedwith image playback as a secondary function
being referred to as Reader 1 and devices
whose primary function is image playback
being referred to as Reader 2.
As the main function of DSCs is to takephotographs, the display inside the DSC istreated as Reader 1. As will be seen later inTable 8.6, with Reader 1, it is not an essential
requirement to display the main image and areduced size image (a thumbnail) can bedisplayed instead.

National Museum of Nature and Science Technology Systematization Survey Report

Vol.10 2008. March

6 DSC Characteristics
The image sensors in DSCs are theequivalent of film in film cameras. While infilm cameras the amount of light received
determines the degree of chemical changethat occurs to form an image, in DSCs, theamount of light received determines thedegree of charge produced that results in theformation of an image. DSCs arecharacterized by the ability to immediately
view the resulting image and the fact that therecording media can be repeatedly reused. A
general comparison of DSCs and silver halide
cameras is shown in Table 6.1.
Table 6.1. A general comparison of DSCs andsilver halide film cameras
DSCs
Structure

Integrated
optics andimage
processing
Advantages
Instant
Low runningcost.
No chemical
processing
required.
Can be written
directly to aPC.
People can dotheir own
image
processing.
Storage does
not require a
lot of space.
No changeover time.
Disadvantages Camera bodyis expensive.
Battery
consumption.

Silver Halide
Film Cameras
Optics – Camera
Photography –FilmCamera body ischeap.
No equipment isrequired to view
images.
Good color
reproduction.
Wide latitude for
exposure.
Minor
deterioration inquality whenenlarged.

Results are
unknown until
the film isdeveloped.
A separate device
is required for
digitization.

However, the differences between DSCs
and film cameras are not simply limited todifferences in image viewing time.

6.1

Sensitivity Properties

DSCs differ from silver halide cameras in
the sense that with silver halide cameras thedevice for creating images (the camera) andthe recording media (the film) are separate
and that it is possible to select various
different kinds of film to use in a single
camera, while with the vast majority of DSCs
it is the camera itself that is the device fortaking photographs and recording images.
With silver halide cameras, optimum image
exposure is achieved by selecting theF-number, which shows the brightness in the
optics system, and the ISO number, whichindicates the sensitivity of the film. Whensetting the exposure manually, bearing film
sensitivity in mind, the optimum exposure isgiven as a recommended exposure index.
By comparison, with DSCs, as the image
sensor used cannot be changed, the optimum
exposure at the time of taking a photograph isdetermined by the DSC used.
In shooting situations such as studio shoots
where strong lighting is used, when incoming
light is acquired immediately prior to the
DSC image sensor becoming saturated, therecommended exposure index is derived fromthe amount of light saturating the DSC image
sensor.
On the other hand, when shooting subjects
in a comparatively small amount of light,
noise in dark areas becomes a problem andthe recommended exposure index is
calculated from the amount of noise.
Furthermore, in normal shooting situations,the recommended exposure index isdetermined so that the image sensor output isapproximately half of the saturation level on
the basis of the luminous intensity of the
midway point in the illuminance distributionof the subject.
Moreover, depending on differences insensor characteristics, there are fundamental
differences between film cameras and DSCs
Systematic Survey on Digital Still Cameras

31

in terms of design, camera characteristics andstructure.
Film is coated with a silver halide emulsion
containing a pigment called a coupler andwhen it is exposed to light the silver
molecules are deposited together with thecoupler. When the silver particles are
removed during the developing process, only
the coupler remains, which brings out thecolor.
If the exposure value (input) is deemed to
be H and coupler density (output) is deemed
to be D, then over a certain range thefollowing coefficient is produced.
D = γ × log(H)Output

The exposure value maintained by thiscorrelation – in other words the optimum
exposure value – is said to be the latitude.
The sensitivity characteristics of negative
film, reversal film and DSC image sensors
are shown in Fig. 6.1.

Negative Film

Reversal Film
Incoming Light

Fig. 6.1. Schematic depiction of sensitivity.
When γ is large, the difference insensitivity with regard to the difference in
exposure value is large, producing what issaid to be a “hard” image, while conversely if
γ is small, then the broad exposure range isexpressed as a narrow output range,
producing what is referred to as a “soft”
image. In terms of the sensitivity
characteristics of negative film, generally, γ issmall. Moreover, as overall it has an S-shaped
sensitivity curve, it can handle a broader
exposure range. On the other hand, withreversal film, as the near γ = 1 range is used,
this range in exposure – in other words the
optimum exposure range – is also narrower
than that of negative film.

32

Therefore, for standard snapshots, etc.,
negative film is frequently used as it ispossible, to a certain extent, to correct
exposure during processing without having toemphasize optimum exposure, while forprinting and graphical materials whereaccurate output is required corresponding to
the exposure value, reversal film is used.
That is to say, while with negative film theemphasis is on obtaining as much informationas possible regarding the subject, withreversal film, as exposure characteristics are
as close as possible to what is seen by thehuman eye, although it is possible to obtainlight characteristics close to those of naturallight by using projectors, etc., as the optimum
exposure range is narrow, it is not suited toshooting subjects with a wide dynamic range
and in some cases lighting is required in orderto keep the subject within the optimum
exposure range. In this respect, negative filmis scene-oriented, while reversal film is
output-oriented.
With standard consumer DSCs, as theimage sensor output at γ = 1 is 8-bit, theoutput range is 1:256, or approximately 24
dB. This means that with compact DSCs
gamma properties are added electrically inorder to provide image characteristics close to
those of negative film.
Furthermore, as with the Fujifilm Super
Honeycomb SR sensor shown in Fig. 7.8,
there are image sensors that aim to effectively
increase latitude by combining two types ofunit sensors (cells) of different sizes.
As previously mentioned, film is coatedwith an emulsion containing silver halide andthe silver particles are arranged irregularly.
By contrast, as the image sensors used in
DSCs are arranged in a regular manner,modulation occurs between the spatial
frequencies of the input signals (image
signals). This is why an optical low pass filter
is essential in DSCs.

6.2

Shooting Time Lag

With DSCs, generally, focusing is carriedout by half-pressing the shutter release button
after which the shutter itself is activated byfully pressing the shutter button. However,when pressing the shutter button from the

National Museum of Nature and Science Technology Systematization Survey Report

Vol.10 2008. Marchhalf-pressed position, in some cases the
shutter is not immediately activated, resulting
in a delay in taking the photograph. In manycases this delay is obvious, especially when
there is a lack of light in the surrounding area.
When the shutter release button ishalf-pressed in a DSC, image sensor output issent to a circuit separate from that used forimage processing and used to measurefocusing distance, meaning that as a result,the optimum focusing distance obtained is
combined mechanically with the optics
system. The image sensor signal used formeasuring distance must be completely
eliminated prior to fully pressing the shutter
release button. Thanks to technicalimprovements, the delay produced throughthis action has gradually been reduced.

6.3

Smear

CCD image sensors use a bucket relay
system to initially transfer the electricalcharge generated in each cell in response to
the intensity of incoming light to a verticalregister, after which it is transferred to ahorizontal register. At that time, if a single
cell is exposed to excessive incoming light, incases where the electrical charge produced is
not able to be fully absorbed by the cell, theexcess electrical charge is superimposed
successively onto other cells in a verticaldirection, resulting in a white linear pattern
appearing on the image. This is known as asmear and is one of the characteristics ofcharge relay-type CCDs. In order to prevent
this, a mechanical shutter is used to blockexcess incoming light.

6.4

Color Filters

There are two types of color filter used in
DSCs, primary color filters (red, green, blue:
RGB) and complementary color filters (cyan,
magenta, yellow and green: CMYG). Primarycolor filters are used where the emphasis ison compatibility with devices using primarycolor signals, such as PCs, etc., and mostconsumer DSCs use primary color filters. On
the other hand, complementary color filters
use a green signal, which is highly visible tohumans, to improve apparent resolution.

Either way, it is possible to change thedisplayed color gamut depending on output
signal calculations, and it is also possible toconvert different color display systems.
Therefore, on many DSCs, it is possible toadjust the white balance by adjusting theoutput signal. This is a function that film
cameras were not capable of.

6.5

Image Stabilization

Most DSCs have an LCD display on theback and in many cases the camera is held at
arm's length in order to be able to see thedisplay when shooting, which means it iseasy for camera-shake to occur. Although
there are even film cameras with image
stabilization, many models of DSC are
equipped with this function.
There are two types of image stabilization,
the electronic type and the optical type.
Electronic image stabilization is unique to
DSCs and camera-shake is removed from theoutput of each cell on the image sensor
through interpolation processing. On theother hand, optical image stabilization uses
signals from devices such as gyros forreference to optically control and maintain aspecific light path, driving the optical systemitself or controlling the light path using things
such as polarizing plates.

6.6

Making Cameras ThinnerWith film cameras, it is not possible to
make camera bodies thinner than the
thickness of the film magazine (the container
holding the film). On the other hand, with
DSCs, as there is nothing to limit thickness, it
is possible to make cameras thinner by
carefully locating the image sensor andbending the light pathway using means suchas a reflective mirror.
With the Minolta Dimage X, which was
released in 2002, it was possible to reduce thethickness of the camera to 20 mm by bending
the light path 90-degrees using a prism. This
made it possible to make a DSC thin enoughthat it could be kept in a shirt pocket,
something that was unthinkable with a film
camera.

Systematic Survey on Digital Still Cameras

33

6.7

Fixed Lens SLRs

With DSLRs, the image sensor input signal
is formed in the finder as a real image using amirror. With this method, there is the
disadvantage of the image in the finder
disappearing at the instant the shutter ispressed because the light path of incoming
light is changed to the sensor. With methods
such as that developed by Fujifilm, the image
from a small CCD is displayed in an
SLR-type viewfinder. Although optically it is
not the real image that is viewed, andresolution is not as good as with a focusing
screen, it is characterized by the fact that theimage does not disappear at the instant the
shutter is pressed.

6.8

Power Consumption

Even with recent film cameras, functions
such as autofocus, zoom, exposureadjustment and flash have been computerized,
and cameras with a continuous shooting
function use electronics to wind on the film,
meaning that in all cases batteries are
required. However, DSCs require more power
because in addition to the various functions offilm cameras, they need to power the image
sensor, image-processing LSI and read andwrite images to and from memory. In order tosolve this problem, efforts have been made to
make low-power electronic circuits andlong-life batteries.

6.9

Autofocus

With autofocus in film cameras, there is theactive type, whereby an ultrasound or infrared
signal is sent from the camera to the subject
and the distance determined on the basis of
the time taken to receive the reflected signal
from the subject, and the passive type, which
adjusts focus optically. The world's firstpassive type autofocusing was developed byKonica Minolta (for compact cameras by theformer Konica and for SLRs by the former
Minolta), and this solved the problem that
active-type autofocus had of not being able tofocus through glass.

34

Fig. 6.2. The principle of autofocus.
As we can see in Fig. 6.2, the response to
the spatial frequency of the subject is at its
highest when the subject is in focus and drops
when it is out of focus. Using this principle,
the position where the spatial frequency
response is highest is sought by moving thelens to obtain optimum focus. However, forsubjects where it is not possible to determine
a spatial frequency, such as a monochromaticwall, it is difficult to obtain an accurate focus
point.
Although a sensor is necessary for focusingwith film cameras, with DSCs, as the output
from the image sensor can be used forfocusing, a dedicated focusing sensor is not
required.

6.10 Digital Zoom
With DSCs, in addition to zooming bychanging the focal length of the lensmechanically, it is possible to use anelectronic zoom function to obtain a telephotoeffect by electronically enlarging the central
part of the image formed on the image sensor.
For example, by enlarging the 1MP area inthe middle of a 4MP image sensor it ispossible to obtain an image twice the size togive an image with a field of view the sameas if it were taken using a lens with a focal
length twice as long. With this electronic
zoom function it became possible to realize a
far wider zoom range with a DSC than would
be possible using a silver halide camera.

National Museum of Nature and Science Technology Systematization Survey Report

Fig. 6.3. Digital zoom.

Vol.10 2008. March

However, the greater the magnification ofthis telescopic effect, the fewer the number ofpixels that are used on the image sensor,
meaning that mosaic patterns in the image
become more significant if left as they are.
In the case of Fig. 6.3, by enlarging anddisplaying the signal for cell E on the image
sensor as four separate image signals (E1, E2,
E3, E4) the image becomes jagged and coarse.
In order to improve this, image interpolation
technology is used to seek signals for
positions equivalent to E1 through to E4 bycalculating using signals from cell E and cells
A, B, C, D, F, G, H and I which border it.
However, if the enlargement ratio is toohigher, then as the number of original source
pixels will decrease, there will be a major
deterioration in image quality with telephoto

images produced electronically as comparedwith telephoto images produced using an
optical zoom.
When using the digital zoom function orchanging image size in DSCs it is necessary
to continually change the number of pixels
that form the image. This also uses digital
filter technology whereby new pixel location
data is interpolated on top of a new image
from the original image. This makes it
possible to reduce the jagged nature ofimages when they are enlarged.
So, with DSCs, we can see that in addition
to zooming by changing the focal length ofthe lens, it is possible to use an electronic
zoom function by electronically enlarging thecentral part of the image formed in the image
sensor to obtain a telescopic effect.

Systematic Survey on Digital Still Cameras

35

7 DSC-Related Technology and
Systematization
Size indicates image quality.

CPs

Contributes mostly to image quality.

High ← Price → Low

Contributes mainly to price.
Contributes mainly to functionality.
Compact DSCs
First
Consumer
Model

Multi-Megapixel
SensorMass
Production
FloppyCameraMemorySensorSensorInternet
Standardization

OpticsColor
Management

Computerization

Megapixels

Digital SLRs

First DSC

Low ← Functionality → High

Fig. 7.1. DSC development.
Technologies that contributed to thedevelopment of DSCs include:
1. Semiconductor Technology(1) Memory(2) Image pickup devices(3) Dedicated LSIs
2. Digital Signal Processing Technology(1) Image processing(2) Image compression(3) Computer OS/image processing
software
3. Color Reproduction Management
Technology
4. PCs and peripherals, such as printers
Optical technologies, such as lens design, andprecision machinery technology, that havebeen developed over many years by
conventional
silverhalidecameramanufacturers, have come to be used in DSCs.
We will now look at some of the maintechnologies involved (Fig. 7.1).

36

7.1

Image Sensors

Among the various technologies that havecontributed to the development of DSCs, themost noteworthy has been the development ofsemiconductors. Image pickup devices andmemory in particular have made a major
contribution to the development of consumer
DSCs. Firstly we shall look at thetechnological progress made in terms ofimage pickup devices.
7-1-1 Multipixels
The DS-1P, the first DSC trialed in 1988,
and the first commercially sold DSC, theDS-X (IMC-100), both used a 400,000 pixel
CCD.
As the purpose of these DSCs was toplayback images on TVs, the design conceptbehind them was that the 307,200 pixels (640× 480) of VGA would be adequate.
Although the Casio QV-10, which was
released in 1995 and pioneered the consumer

National Museum of Nature and Science Technology Systematization Survey Report

Vol.10 2008. Marchmarket, and the QV-10A that was released
the following year were both designed toreplay images on a PC display, they only had
250,000 pixels.
However, when replaying on a PC monitor,
it is possible to replay images using standards
that have a higher resolution, such as SVGA
(Super VGA = 800×600 pixels), XGA(eXtended Graphic Array = 1,024×768
pixels), SXGA (Super XGA = 1,280×1,024
pixels) or UXGA (Ultra XGA = 1,600×1,200
pixels) and to display multiple or enlarged
images through the use of image processing
without being limited by the number ofpixels.
However, when printing out images,
TV-quality images are inadequate and an
image the size of a business card requires
approximately 1 million pixels.
In line with such demands, DSCs featuring
CCDs with more than 1 million pixels werereleased in 1997, such as the Fujix DS-300(Fujifilm), Camedia C-1400 (Olympus) andthe Konica Q-M100 (Konica), followed in1998 by DSCs with more than 2 million
pixels, such as the EOS D2000 (Canon),Dimage RD3000 (Minolta), FinePix700(Fujifilm) and Nikon D2 (Nikon).
After that, the number of pixels continued
to increase and as of 2007 there are models
with more than 10 megapixels (10MP).

However, if the size of the individual cells
is reduced, as the charge produced per cell in
response to the same amount of light isreduced, unless noise produced by darkcurrents when there is no incoming light isreduced, the signal to noise ratio (S/N ratio)
drops, producing images with a lot of noise.
Furthermore, if the size of the image sensor
itself is increased, then the yield rate at which
absolutely defect-free sensors can beproduced drops. In 1992, the Society for
Imaging Science & Technology (IS&T)
announced that sensor yield rate wasinversely proportional to size cubed, and as
yield rate drops to 1/8 if sensor size isdoubled, this led some to believe that thecommercialization of large image sensors
would not succeed.
What made large image sensors possible
was the fact that the signal from a defective
cell could be corrected by image interpolation
technology using the signals of surrounding
cells, meaning that an image sensor could still
be used even if it had a certain number ofdefective cells. This made the production of
low-cost image sensors a reality.
According to statistics regarding DSC
image sensor pixel numbers released by
CIPA, although in 2000 it ranged from under
1MP, to 1MP–2MP, to 2MP or more, from2006 this changed dramatically, ranging fromunder 6MP, to 6MP–8MP, to 8MP or more.
Those trends are shown in Fig. 7.2.
(Unit: 1,000 JPY)

Fig. 7.2. The trend toward higher pixels
numbers [1].
There are two conceivable ways to increase
the number of pixels:
1. Decrease the dimensions of individual
cells, or
2. Increase the overall size of the image
sensor.

Fig. 7.3. Trends in the number of pixels(Megapixels) [2].
Figure 7.3 shows average price trends for
DSCs according to the effective number ofpixels on the image sensor. While the price of
DSCs with the same number of pixels is
dropping each year, by making new products
Systematic Survey on Digital Still Cameras

37with more pixels the main focus, such models
are supporting the DSC market overall.
7-1-2 Proprietary DSC Image Sensor
Development
A single image is divided into minute
pixels and the signal from each pixel is output
consecutively. The process of outputting thisdata is called scanning and as we can see
from Fig. 7.4, there is interlaced scanning(left hand side) and progressive scanning(right hand side).

Fig. 7.4. Interlaced (left) and progressive(right) scanning.
Movies and videos are recognized as
moving images by the human eye by
consecutively presenting still images. One of
the characteristics of the human eye is thatthe shorter the interval between the still
images presented, the more the movement isperceived as being fluid with little flicker.
The point at which that occurs is 1/50th of asecond. Therefore, with an emphasis on
improving flicker on consumer video movie
cameras, interlaced scanning was adopted. As
can be seen on the left in Fig. 7.4, withinterlaced scanning, scanning is first carriedout at approximately 1/60th of a second, as
shown by the solid lines, followed byscanning at approximately 1/60th of a second
as shown by the dotted lines. This is referred
to as odd scanning and even scanning, and theimages obtained are referred to as odd fields
and even fields.
When interlaced scanning is carried out, theimages are perceived to be more fluid, withless flicker, than progressively scanned
images, where entire frames are scanned
consecutively and presented approximately
every 1/30th of a second, as shown on theright in Fig. 7.4,.

38

Fig.7.5 Movement shot with interlaced
scanning.
Incidentally, with interlaced scanning, as atime difference arises when scanning odd andeven fields, if a moving subject is shot as
exaggerated and shown in Fig. 7.5, then adiscrepancy (smear) in the image will be
produced.
With the first DSCs, as the performance of
CMOS sensors was poor, as we will see later,interlaced scan-type CCDs (IT-CCD) forvideo movie cameras were used. However, if
IT-CCDs are used as they are for recording
still images, then the above-mentioned
problem will occur.
In terms of CCDs for DSCs, in order to
exclude this kind of defect, although the
Frame Interline Transfer CCD (FIT-CCD)
was developed that placed a frame-likestorage area around the charge transfer
register, this resulted in a more complex
structure with the disadvantage of reduced
sensitivity as compared with an IT-CCD of
the same size.
Therefore, with compact DSCs using a
CCD, either a FIT-CCD or an IT-CCD with amechanical shutter is used, and after all cells
have been exposed to light, they are read andinterlaced.
With video cameras, although the camera isnever used on its side to shoot footage, with
DSCs, sometimes the camera is turned on its
side to take photographs, such as when taking
portraits. The aspect ratio of video camera
image sensors (the width-height ratio of asingle cell) uses non-square pixels for ease of
signal processing.
As mentioned in Chapter 3, image sensor
output, which is the aggregation of solitary
waves, can be converted by Fourier transformto the aggregation of the continuous
frequency spectrum inside the image sensor.
Therefore, after converting the output fromeach cell on the image sensor arranged atinterval T1 (as shown in Fig. 7.6) to a

National Museum of Nature and Science Technology Systematization Survey Report

Vol.10 2008. Marchcontinuous signal, it is possible to treat it in
the same was as when using an image sensor
with square pixels by resampling it at thesame interval T2 in a vertical direction andhorizontal direction.
This works by passing the signal, which has
been read at a set time interval t1 from eachcell on the image sensor, through a low-passfilter and then capturing it at a common timeinterval t2 vertically and horizontally.
However, while it is possible in this way touse an image sensor with non-square pixels tocreate a signal equivalent to one obtained
from an image sensor with square pixels, insuch a case the maximum vertical andhorizontal spatial frequencies are different
and the resolution is different vertically fromwhat it is horizontally.

Fig. 7.6. Cell output resampling.
Therefore, with DSCs, it is preferable thatthe image sensor cells are square and that allcells are configured in such a way that they
are exposed to light simultaneously. Given
this need, it was necessary to independently
develop image sensors for use with DSCs,
despite the fact that in the early 1990s when
the DSC market had yet to take off it wasdifficult to develop new image sensors
intended only for use with DSCs.
7-1-3 Commercialization of CMOS
Image Sensors
With CMOS sensors, as it was possible toform the CMOS logic section on the sameboard, the power supply was more simple
than for a CCD, and the smear produced with
CCDs (when bright light produces a chargethat overloads the charge storing section it
bleeds to adjacent cells, resulting in a straightline of light being formed on the image) did

not occur, it was hoped that they could be
used as elements in multipixel image sensors.
However, with CMOS, as each element isread individually, when shooting a moving
subject the time at which each cell is readdiffers, meaning that distortion will be
produced. In order to prevent this, it isessential to use a mechanical shutter.
Furthermore, as mentioned in the previous
chapter, with CCDs, during the final stage ofthe bucket relay the signal is amplified by asingle amplifier, while with CMOS sensors
each cell has its own amplifier, meaning that
it was difficult to suppress variation on acell-by-cell basis. This is why CCDs havebeen used for so long despite disadvantages
such as high power consumption, the need for
multiple power supplies and difficulties withincreasing speed.
On the other hand, Canon developed theirown proprietary CMOS sensors and byimproving the manufacturing process andreducing noise by storing dark currents fromeach cell in an image processor theysucceeding in commercializing CMOS sensors,
using an APS-size CMOS sensor in the EOS
D30 released in 2000.
Since then, on the basis of the merits
outlined above, CMOS sensors have come tobe widely used in multipixel DSCs such as
DSLRs.
7-1-4 Special Configuration Image
Sensor Development
Fujifilm developed the Super Honeycomb
CCD in 2000 and released the FinePix 4700Z,
with the equivalent of 4.32MP, into the
2.4MP CCD market. As can be seen in Fig.
7.7, this Super Honeycomb CCD ischaracterizedbyphotodiodes
withoctagonal-shaped openings arranged in acheckered pattern.

Fig. 7.7. Honeycomb CCD [3].
Systematic Survey on Digital Still Cameras

39

Although the accumulated signal charge issequentially transferred through the verticaltransfer register in the same way as with an
IT-CCD, these vertical transfer registers arearranged in a zigzag pattern between thephotodiodes.
As a result, compared with conventional
IT-CCDs, the Super Honeycomb CCD,
highly sensitive due to the large area of its
photodiodes,
has
1.4
times
the
horizontal/vertical resolution of IT-CCDs dueto the fact that horizontal/vertical pixel pitch
is 0.71 times that of IT-CCDs. Furthermore,as in the natural world there are manyhorizontal and vertical edges, and in terms ofhuman optical characteristics we are moresensitive to horizontal and vertical directions
than we are to diagonals, this type of CCD
also provides more of a sense of highresolution visually.
In 2003, Fujifilm developed fourth
generation Super CCD Honeycomb sensors,which were called the Super CCD
Honeycomb HR and the Super Honeycomb
SR, with the former being used in the FinePix
F410 and the latter being used in the FinePix
F700.
Figure 7.8 shows the Super Honeycomb
SR II. This featured a honeycomb
arrangement with two different types of cellsof different area: highly-sensitive S cells andR cells to increase the dynamic range.
This was similar to the structure of the film
used in silver halide cameras, where
highly-sensitive large silver halide particles
and low-sensitivity fine silver halide particles
that became light-sensitive when exposed tohigh-intensity light were combined into thecoating.

S pixelsaturation point

S pixel photoelectric conversion characteristics
R pixelsaturation point

R pixel photoelectric
conversion characteristics

Signal range used to reproduce image at ISO100

Fig. 7.9. Super CCD SRII characteristics [5].
In other words, as can be seen in Fig. 7.9,
while improving sensitivity using S cells, R
cells dealt with high-intensity light thatover-saturated S cells, meaning that overall
the sensor was designed to work with a broad
range of incoming light and had a dynamic
range that was four times greater thanFujifilm's previous models.
On the other hand, Foveon, Inc. developed
the Foveon X3 image sensor (Fig. 7.10) that
improved resolution by using a multilayer
structure consisting of three sensor layers,
each corresponding to one of the three
primary colors, releasing the first model withthis sensor, the Sigma SD9, in 2002.
This sensor was similar in structure to thecolor film used in silver halide cameras in thesense that the cells comprising each layer
corresponded with a single color.

Fig. 7.10. Foveon X3 structure [6].

7.2

S pixelR pixelFig. 7.8. Super CCD SR II structure [4].

40

The Invention of Flash
MemoryEarly DSCs, such as the DS-1P and the
DS-X, used memory cards with SRAM chips
as recording media that required a small
battery. Not only did this mean that a backup
battery was required, but that storage capacity
was limited to approximately 2MB, which isextremely small and capacity was limited to

National Museum of Nature and Science Technology Systematization Survey Report

Vol.10 2008. Marchabout ten images. Toshiba then invented flash
memory, which is compact, long-lasting,easily rewritable and does not require a powersource. As large-capacity memory became
available at a cheap price, the position of
DSCs was further strengthened in terms of
their economy and instant nature.
It would be certainly no exaggeration to saythat the single greatest driving force behind
DSCs that has allowed them to develop into
what they are today has been flash memory.
Flash memory is a type of Electronically
Erasable Programmable Read-Only Memory(EEPROM) and as each chip is comprised ofa single element, the area of each unit is small,which makes it possible to manufacture
large-capacity memory chips.
This flash memory was invented by Dr.
Fujio Masuoka (presently Professor Emeritus
at Tohoku University) while researching
semiconductors at Toshiba during the 1980s.
Featuring a novel structure whereby charge
accumulated in a floating gate using quantum
tunneling, this invention was widely
acclaimed both within Japan and throughout
the world.
A model of the structure of flash memory is
shown in Fig. 7.11.
Control gate
Floating gate
Drain

SourceFig. 7.11. Flash Memory structure [7].
When writing (W) to flash memory, there is
0V on the source, 18V in the drain and an
18V electric potential is applied to the control
gate, exciting electrons in the vicinity of thechannel causing hot electrons, which are
acquired by the floating gate through themetal oxide film by means of quantum
tunneling. As these electrons are insulated
from their surroundings, they are trapped
semipermanently.

Control gate

Control gate

Drain

Floating gate
SourceFloating
gate
SourceInitial state.

Drain

Written state.

VD=ConstantInitial state.

Written state.

Shift

Fig. 7.12. The principle of writing to andreading from flash memory [8].
The principle behind reading from flash
memory (R) is shown in Fig. 7.12. The
horizontal axis of the graph represents thevoltage applied to the control gate, while thevertical axis represents the current that flows
between the source and the drain at that time.
When there is no charge on the floating gate,
such as shown on the left, and a voltage of 1Vor more is applied to the control gate, thencurrent flows. This is referred to as having athreshold voltage of 1V.
On the other hand, when electrons aretrapped in the floating gate, such as shown in
the top right graphic of Fig. 7.12, as thevoltage applied to the control gate is initially
captured by the charge of the floating gate
and does not affect the channel, the only
current to flow between the source and thedrain is when a voltage of 6V or more isapplied to the control gate. Therefore, byapplying a voltage of between 1V and 6V tothe control gate and checking whether or notthere is any current, it is possible to readwhether the signal written in the control gate
is a 0 or a 1.
When erasing data (E), as shown in Fig.
7.13, a high-voltage positive charge is applied
to the erasing gate, pulling the electron off thefloating gate.
As writing and erasing is carried out using
tunnel currents, less power is consumed thanSystematic Survey on Digital Still Cameras

41with the SRAM used previously, meaningthat flash memory uses only about 1/10 of thepower used by Hard Disk Drives (HDDs) of
the same capacity.
Control gate

Floating gate
Erasing gate

Si substrate

Fig. 7.13. Erasing flash memory [9].
Dr. Masuoka came up with the concept forthe structure of flash memory around 1980
and in June 1984 presented papers regarding
it at the IEEE's International Electron Devices
Meeting(IEDM)andInternational
Solid-State Circuits Conference (ISSCC).
Although Dr. Masuoka saw flash memory
as a recording media to replace HDDs, he
was assisted in his research by the divisionthat was developing DSCs within thecompany and together they were able tocreate prototype 4MB NAND flash memory
in February 1983, release it in December
1984 and present it at the International Solid
State Circuits Conference (ISCC) in San
Francisco in February 1985.
There are two main types of flash memorythat use memory with 1-byte (8-bit) units:
NOR and NAND.
Dr. Masuoka described it thus: NOR is likehouses with individual entrances, while
NAND is like an apartment building with acommon entrance.

MemoryMemoryMemoryMemoryMemoryMemoryMemoryMemoryMemoryMemoryFig. 7.14. NOR structure [10].
As shown in Fig. 7.14, NOR memory
consists of a single memory cell connected
between a bit line B and an earth.
If there is a charge between any one of the42

memory cells that are connected to a single
bit line, then the electrical potential drops,
meaning that all of the connected memory
cells do not operate. In order to operate theselected memory cell, all that is required is tomake all of the bit lines other than the bit line
connected to that memory cell charged and tocontrol the write line (W) of the memory cell.
On the other hand, as we can see from Fig.
7.15, NAND has series-connected memory
cells.
When reading from (R) or writing to (W) aselected memory cell, an electrical potentialof 0V is applied to the gate of that memory
cell while an electrical potential of 5V isapplied to the gates of other memory cells.
This causes all of the memory cells other thanthe one selected to be in a state of conduction.
When reading from a memory cell, if theselected memory cell is 0, then the bit line is
non-conductive, while if it is 1 then it isconductive. When erasing, the electrons are
displaced from all of the floating gates and allbits are in the 1 state.
Although random access is not possible
with this NAND EEPROM like it is with
NOR, it can be compact with a large capacity
and low power consumption, and it is ideallysuited to writing large blocks of data at a time,such as image data.
BL bit line

Fig. 7.15. NAND structure [11].

7.3

Memory Cards

7-3-1 PC Cards
In 1985, an IC memory card technology
expert committee was established in JEIDA[12] and discussions began regarding the

National Museum of Nature and Science Technology Systematization Survey Report

Vol.10 2008. March

1. CF: CompactFlash cards were proposed by
SanDisk Corporation in 1994 and thespecifications were determined by theCompactFlash Association (CFA). The
block diagram of a CF card is shown in Fig.
7.16.
As external input/output is based on the
ATA standard, a CF card can be treated in
the same was as an HDD by the host. The
properties of the internal memory are

Reset IC

Oscillator
Controller

Flash
Memory Bus
Flash
MemoryControl
SignalFig. 7.16. CF card block diagram [14].
2. SM (SSFDC＝Solid State Floppy Disc):
Smart Media is a postage stamp-sizedcompact, thin NAND type of flash memory
card announced by Toshiba in 1995 andhas dimensions of 37 (W) × 45 (L) × 0.76
(T) mm, a capacity of between 2MB and
128MB and uses a common 22-pin
interface regardless of capacity. As isshown in Fig. 7.17, this interface is an I/Ointerface comprised of an 8-bit parallel bus
and is able to be controlled by assigning
two I/O addresses [4].

Single Chip

I/O read, I/O write

Smart Media Connector

7-3-2 The Birth of Various Memory
Cards
Flash memory came to be used in memory
cards in place of conventional SRAM. At thesame time, in addition to the PC cards that
had mainly come to be the standard type ofcard used in laptop PCs, various othermemory cards were introduced, such as the
CF card in 1994, the SM card in 1995, theMMC card in 1997 and the MS card in 1998.
Of these memory cards, CF cards had alarge capacity and were ATA compatible, SM
cards were thin and contained only memory,and MS cards had a serial I/O interface,
meaning that each had their merits and thevarious DSC manufacturers selected them foruse in DSCs in light of those merits.
I will now provide an overview of the maintypes of memory card used in DSCs since thelatter half of the 1990s, which include CF,
SM and MS cards.

absorbed in the controller, meaning they do
not influence the host. Furthermore, as it ispossible to internalize large-capacity
memory, they can be connected to a PC
card slot by means of a simple passive
adapter.
The external dimensions are 42.8 (W) ×36.4 (L) mm and Type I cards have athickness of 3.3 mm, while Type II cards
have a thickness of 5 mm.

Address Decoder

creation of a memory card standard. In 1989,
the Personal Computer Memory Card
International Association (PCMCIA) [13]was established in the US and although thesame kind of matters were considered, theJapanese extended an invitation and in 1990
the decision was made to work on the issue
together, resulting in the establishment of
unified PC card standards in 1993.
With early DSCs, PC cards with SRAM
memory elements were used as recording
media for images. As SRAM requires anexternal voltage to be applied in order tomaintain recorded data, a small battery wasbuilt into these PC cards for backup. As thestorage capacity of SRAM was small, thestorage capacity of PC cards wasapproximately 2MB, which is extremely
small.

SoftwareApprox. 40 kB

Fig. 7.17. Smart media interface [15].
One of the characteristics of SmartMedia
was that the cards were extremely thin, but
prompted by calls for expanded capacity
Systematic Survey on Digital Still Cameras

43and improved security, Toshiba announced
the successor to SM card, the xD card, andalso announced the Secure Digital (SD)card, which they developed in cooperation
with Panasonic.
3. MS: The Memory Stick was announced bySony in 1998. One of the characteristics
was that it had a bus state controller-typeserial interface to interface with the host.
The MS block diagram is shown in Fig.
7.18.

individual merits, such as whether or not it
has internal memory controllers or security
features, etc. At present, there are models on
the market with a capacity on par with that of
HDDs, and when used for DSCs, even though
the various cards may be different, the datastored on them is the same, regardless of whatkind of memory card is used.
The main memory cards being used as of2008 are shown in Table 7.1.
Table 7.1. The main types of memory card
Major Types

Controller

Product

FlashRegisterPage Buffer

Flash
IF
Sequencer

Reset

Fig. 7.18. Memory stick block diagram [16].
The Memory Stick family included theMemory Stick PRO, which made large
capacity high-speed data transfer possible,
the small Memory Stick Duo and the evensmaller Memory Stick Micro (M2).
A situation where image format differs
according to the type of recording media
wouldinconvenience
DSC
users.
Furthermore, should unnecessary disputes
arise regarding which type of recording
media and format is better, consumers would
refrain from making purchases.
In order to avoid such a situation, Japanproposed the Exif and DCF formats, which
are not reliant on recording media, and has
succeeded in having most of the consumer
DSCs in the world at present use theseformats.
Not only are all of these memory cards
different in terms of external dimensions andfunction, but the formats in which DSC
images are formed and stored are also
different, depending on the memory cardused.
On the other hand, in addition todifferences among the memory chips used,
there are at present a number of different
types of recording media on the market, suchas the various types of memory cards, witheach being used on account of its own

44

7.4

Digital Signal
Technology

Processing

It is possible to perform various kinds ofsignal processing on DSC image sensor
outputs that have been converted into digital
signals by the internal A/D converter using
the digital properties of the signal.
Because DSCs could digitize and thenutilize such data, it was possible to carry out
image processing within the camera thatwould have been difficult with silver halide
photographs. This made it possible toimprove image quality, reduce the price of
DSCs and provide new features.
While early DSCs had a single
multipurpose central processing unit (CPU)referred to as a single-chip microcomputerthat carried out such processing, with the

National Museum of Nature and Science Technology Systematization Survey Report

Vol.10 2008. Marchmass production of DSCs, such processing
has come to be handled by a special LSI
called an image processing engine, or is
performed within the DSC by the CPU. The
target of such processing and the algorithms,
etc., involved are the know-how of thevarious companies and are one of the things
that differentiate their various DSCs from one
another, and each of the companies is also
involved in developing their own proprietary
LSIs.
We will now look at a number of thetechnologies that have been employed indigital signal processing. Only after digital
signal processing became a reality were thesetechnologies able to be commercialized andthey are what have clearly distinguished
DSCs from earlier electronic cameras.
7-4-1 Image Effect Processing
As shown in Fig. 7.19, the Spatial
Frequency Response (SFR) of DSCs drops as
the spatial frequency of the subject increases
and is 0 at the cutoff frequency (fc).
Although response characteristics once
again appear with spatial frequencies of fc
and above, this is due to intermodulation andas this becomes a source of noise called
artifacts it must be removed. Therefore, DSCs
are equipped with an optical low pass filter
that uses crystal birefringence, etc., to shutout the spatial frequency components of fc
and above.

Fig. 7.19. Frequency response characteristics.
On the other hand, if the high frequency
component in spatial frequency response
characteristics is sharply cut off at fc, theoutline of the subject will not be clear andvisually the image will seem “soft.” In order
to correct this, in many cases edge
enhancement is employed to raise spatial
frequency response characteristics in thevicinity of fc using a digital filter. However,as excessive edge enhancement will appear
unnatural, just how such edge enhancement iscarried out comes down the know-how ofeach individual company.
This kind of image processing is carried out
using the unique algorithms in the proprietaryprocessors of each company. These
processors are also used for pixel
interpolation (as mentioned in greater detailbelow), meaning that even if there are anumber of defective pixels on an image
sensor, defective pixels can be compensatedfor before output images are displayed,something that has greatly contributed to theimprovement of yield rates in the
manufacture of image sensors.
7-4-2 Image Sensor Defect Correction
While it is necessary for each cell on animage sensor to have uniform characteristics,
the yield rate for large image sensors that are
free from defects in all cells and with evencharacteristics is extremely low and it was notthought to be commercial viable from amanufacturing perspective.
If when shooting still images using ananalog signal there were any defects in thecells of the image sensor, then corresponding
areas in the output image would be missing,and the sensor would therefore have been
considered to be defective.
However, if the signals from the cell are
stored as digital data, by interpolating datafrom the cells surrounding the defective cell it
is possible to use image sensors withdefective cells that would have previously
been considered to be defective, somethingthat has greatly contributed towards reducing
the costs of DSCs.
Generally, a filter with the following
properties is used for this pixel interpolation:sin(x)/xIn this way, based on pixel data fromneighboring cells, data for the location of thedefective cell can be interpolated. This is atechnology that was impossible withconventional VTRs and because thistechnology was first commercialized only
after digital technology had been introduced,
it is no exaggeration to say that it made a
Systematic Survey on Digital Still Cameras

45

major contribution to reducing the price ofDSCs.
7-4-3 De-mosaicing
Normal DSCs use a single-plate image
sensor and have a color filter on the surfaceof each cell on the image sensor, allowing
only a certain color to pass through primarycolors (RGB) or complementary colors(CMY). For example, cells with an R filter
only reproduce an R signal.
Therefore, in a DSC with, for example, a
4MP single-plate primary color image sensor,
there will generally be 1MP of R pixels, 1MP
of B pixels and 2MP of G pixels.
However, when carrying out image
compression, in situations such as outputting
to an external device, data for all three
primary colors in each cell location is sought.
Therefore, in a DSC, the G and B signal for
an R cell is interpolated and reproduced using
digital filter technology from neighboring G
and B signals.
Furthermore, by using pixel interpolation,
while, for example, data from a 3MP CCD
can be output as 4MP recording pixel data, it
is important to remember that pixel
interpolation does not create new data, but isa technology that converts the original image
data into the necessary format without data
loss.

7.5

Optical Technology for DSCs

Lens design and flare countermeasures are
optical technologies that have been developed
over many years by silver halide camera
manufacturers. Philipp Ludwig von Seidel
grouped spherical lens aberrations into fivedifferent categories: spherical aberration,coma, astigmatism, curvature of field, anddistortion, in addition to chromatic aberration.
How to suppress these is one of the important
themes of lens design.
Furthermore, with an ideal lens, when thesubject is a light source, the image is formedon the image pickup device in the position
where it is completely in focus, and if thelight source is move backwards or forwards,
then the image goes out of focus. However, in
reality, even if the light source is moved
backwards or forwards, there is a certain46

degree of tolerance with regard to where theimage can be formed and still be in focus.
The permissible range of the light source atthat time is called the depth of field. Depth offield is reliant on the size of the image pickup
device and the smaller the image pickup
device, the greater the depth of field.
In DSCs with an image pickup device
smaller than 35 mm film size, as the depth offield will be greater than that of a 35 mm
silver halide camera, there is the disadvantage
of it being difficult to create nice bokeh effect(out-of-focus background blur) in situations
such as shooting close-ups. This problem has
been solved in recent DSLR cameras, where
the image pickup device used is equivalent to
the 35 mm size.
In many cases, the development of early
DSCs was carried out by the video camera
development departments of consumer
electronic
manufacturers,orby
non-mainstream electronic technicians in thevarious camera manufacturers. Therefore, as
it was difficult to design dedicated optics forearly DSCs, in some cases existing lenssystems were cannibalized with relay lenses
to convert the light path.
The optics of the IMC-100 developed by
Toshiba were reliant on Fuji Photo Film Co.,
Ltd., while for the optics of the IMC-200
Toshiba was unable to gain the cooperation of
specialized optics companies within the
Toshiba group, and instead had to contract
them out to a specialized lens manufacturer.
When it was clear that the DSC market was
rapidly growing while the market for silver
halide cameras was dramatically shrinking,the various companies hired outstanding
optical technicians to work on the design of
optics for DSCs and the performance of
DSCs notably improved.
7-5-1 Oblique Incident Light
Film comprises stacked photosensitive
layers for the various colors, so that even if
there is a problem with color shift due tooblique incident light, it has little influenceon photosensitive efficiency.
On the other hand, the photoelectrictransducers of semiconductor image sensors
have a layered structure, as seen in Fig. 7.20
and each individual photodiode (cell), which

National Museum of Nature and Science Technology Systematization Survey Report

Vol.10 2008. Marchis the photosensitive element, is located in
the bottom of a well formed in thesemiconductor substrate.
On account of this, if incident light isanything other than perpendicular, then theamount of light will decrease. Furthermore,as the color filter mounted on each cell isefficient at receiving incident perpendicular
light, and is designed to operate as an
accurate color filter, not only will
photoelectric conversion efficiency drop withoblique incident light, but it is feared that it
will impede accurate color reproduction.
Moreover, with small-aperture lenses, as
incident light diverges from the perpendicularin the area around the image sensor to
become oblique incident light, the error
increases.

Microlens

7.6

Color Reproduction
Management

Electromagnetic waves fill the environment
in which we exist and the wavelengths thatare visible to the human eye are extremely
limited, ranging from 360–400 nm (1 nm =1/106 mm) on the shortwave end to 760–830
nm on the long-wave end (Fig. 7.21).
As shown in Fig. 7.22, the human retina
consists of two types of visual cells,
rod-shaped cells that detect only the intensityof comparatively weak incident light, andcone-shaped cells that detect the chrominanceof comparatively stronger incident light.
There are three different types of cones thatreact to red (R), green (G) and blue (B) andwhich exist on a ratio of approximately
32:16:1. While there are approximately 100
million rods, there are only about 7 million
cones, which are concentrated around thecentral area of the visual axis called the fovea
centralis, as shown in Fig. 7.23.
Wavelength (mm)Black-out Film

Frequency (Hz)Cosmicrays

Color Filter

PhotodiodeFig. 7.20. Oblique incidence.
Therefore, lenses for DSCs are designed tohave a larger aperture the closer they are to
the image sensor in the interest of making thelight coming into the sensor as perpendicular
to the sensor as possible.

Vacuumultraviolet

VioletIndigo
藍

Gamma
ray

Ultraviolet
X-rays

Blue

Green

Light
Visiblelight

Scattering
measurement

Light
rays

Yellow
OrangeInfraredRadarRed

7-5-2 Flare
While it is desirable that the inside of thecamera itself be completely dark, some of thelight passing through the lens is reflected
when it hits the film or image sensor
positioned on the focal plane, leaking into theinside of the camera. This is a phenomenon
known as flare and as the surface ofsemiconductor image sensors has a higher
degree of reflectance than the surface of film,
countermeasures, such as surface treatments,
are required to suppress the flare.

Near
infrared

Television
WirelessRadio

Far-infrared

Low-frequency

Fig. 7.21. Electromagnetic radiation
wavelengths [17].

Systematic Survey on Digital Still Cameras

47

Pyramidal cell

Rod cells

Outer segment

Inner segment
Photoreceptor cells

Horizontal cell
Bipolar cell

Amacrine cellFig. 7.24. Brightness estimation [20].

Ganglion cell

Light

Fig. 7.22. Structure of the retina [18].
In other words, while the large number ofrods is used for overall sight, color
differentiation is mainly carried out by conesin the central area of the visual axis.
The diameter of the rods and cones in theouter segment shown in Fig. 7.22 is 1–2 µm
and 1–5 µm respectively. Incidentally, thediameter of the silver halide used in silver
halide photographs is 0.05–3 µm. The densityof the visual cells in the vicinity of the fovea
is approximately 60,000/1 mm2, meaning that
there are more of them than theapproximately 15,000 (12MP, 35 mm size)
pixels used in DSCs and the approximately
30,000 grains used in color film photographs.

Visual cell density (mm−2)

Blind spot

Ear

Fovea

Nose

Fig. 7.23. Rod and cone distribution [19].

48

As shown in Fig. 7.24, illuminance in thenatural world ranges from direct light on the
coast during mid-summer to starlight at night,
ranging from 105 lx to 10-3 lx or less, which isactually eight decimal places or 160 dB or
more.
The human eye is capable of adapting tothis wide range of brightness by adjusting theamount of light via the pupillary light reflex
and using cone cells that are sensitive inbright light and rod cells that are sensitive in
dim light.
By contrast, consumer DSCs are 8-bit; inother words, when used as they are they have256 colors and a dynamic range of only
approximately 48 dB. With DSCs, theaperture is adjusted to optimize exposure andcope with changes in lighting conditions.
In order to accommodate the brightness
range of the subject, there is the choice ofeither capturing an encoded image with the
dynamic range compressed in a non-linear
fashion for a wide brightness range, or
capturing an image with the range limited tothe appropriate level.
In the case of the former, even if optimum
exposure is not set, it can to a certain degree
be compensated for, but there will be adiscrepancy in the value used non-linearlyand noise will be produced. On the other hand,with the latter, although the linearity of color
reproduction is outstanding, it results inimages that are impossible to repair when the
optimum exposure is not set.
On the other hand, because perception ofcolor by the human eye is carried out by thethree types of cone cells as already mentioned
above, this three primary color theory is
widely used in DSCs and other imaging
fields.

National Museum of Nature and Science Technology Systematization Survey Report

Vol.10 2008. MarchWhen recording in recording media ascompressed images, these color values arerecorded as they are and converted into RGB
when rendered on a PC display.
Moreover, when images are printed on a
printer, color must be converted to CMYK
values (the subtractive CMY values withblack (K) added). This process is depicted inFig. 7.26.
Fig. 7.25. Color matching in the RGB color
space [21].
In 1931, the International Commission on
Illumination(CIE:
Commission
Internationale d'Eclairage) [21] introduced
the CIE 1931 RGB color space, which wasdemonstrated to be able to approximate anycolor by color matching the three primarycolors – R (700.0 nm), G (546.1 nm) and B(435.8 nm) – which are called the reference
stimuli.
However, as shown in Fig. 7.25, between
435.8 nm and 546.1 nm, R must be negative.
This represents adding R to the subject color
to make a mixture of G and B to match it. As
negative color does not actually exist, it is notpossible to make colors in this fashion. For
this reason, the theoretical reference stimuli X,
Y and Z, were introduced as the XYZ color
space to avoid negative RGB values.
Although color-matching functions in thisxyz color space are represented by x, y and z,
generally
x+y+z=1
and the two-dimensional x and y coordinates
are used to express chromacity.
PCs and other IT devices commonly use the
RGB color model, but television signals
reproduce color using the YCbCr color spacewith luminance (Y) and chrominance (Cb andCr) signals.
Color information in DSCs is reproducedwith the three primary colors in the same way
as with the human eye.
Although DSC image sensors use filterswith the three primary colors (RGB), or theircomplementary colors cyan, magenta andyellow (CMY), as JPEG is compatible withcomposite signals, RGB signals are converted
to and stored as YCbCr values.

Fig. 7.26. DSC system color display
overview.
Exif adopted the sRGB color space that was
initially determined by the International
Electrotechnical Commission (IEC)'s TC100
as IEC 61966-2-1. This sRGB color space wasfor color management on CRT displays, and is
optimized for that purpose. On the other hand,printers and other peripherals can reproduce awider range of colors than CRT displays, andit was suggested that color management wasinadequate with sRGB. Consequently, DCF
2.0 added support for Adobe RGB, a color
space often used in desktop publishing (DTP),
etc., that has a wider gamut than sRGB.
DSCs capture images of physicalphenomena (subjects) in the form of digital
data, accumulate them in the logical realm,
and output them as digital signals to displays,
printers and PCs, etc. after image processing,etc.
During that process, such physicalinformation only becomes visible whenviewed on a display, such as a DSC LCD.
In other words, as depicted in Fig. 7.27,
image data in DSCs is handled in the logicalrealm, and can be perceived as physicalinformation via interfaces such as printersand displays.
For us, only when this physical information
is made visible via these interfaces can we
Systematic Survey on Digital Still Cameras

49perceive digital images.

Perceptual domain

Exif data

RAW data

Data after image
processing
Logical realm

Fig. 7.27. Perceptual realm/logical realm
image flow.
In terms of the concept of color
management, which involves the handling ofchromacity, saturation and luminance, color
encodings based on faithfully taking the colorof the subject and reproducing it on the basisof the subject are thought of as being
input-referred, while color encodings
designed for color reproducibility on thedevice that reproduces the exposed image arethought of as being output-referred. This
concept as it applies to images is known as
image state (Table 7.2).
Table 7.2. Image state

Like with a photocopy, etc., when it ispossible to evaluate equivalence if an output
image is in the same form as the subject, it ispossible to carry out color management basedon the “subject color.” Requirements change,
however, depending on illuminating light andother environmental factors that influenceviewing conditions when images on
two-dimensional media such as paper or PC
are used to display subjects that are naturalobjects (existing in three-dimensional space
like the DSC itself). When this happens, color
reproduction management is standardized to“remembered color” or “pleasant color.”
If a color is within the realm of
reproducibility, it is possible for that color to
be changed via mathematical operations.
There are many software programs on themarket for changing the color of and applying
effects to DSC images.
Although the range of color that can be
captured by DSCs is determined by thecharacteristics of the filters used in them,even DSCs using sRGB for a color space arecapable of taking a wider gamut of color thanis possible to reproduce within the confines ofthe sRGB color space. However, when thecolor signal output of DSCs is written using
the sRGB color space, colors outside of thesRGB gamut are “clipped” (thrown away).

Input Referred
Scene Referred • • • DSC
Original Referred • • • Copy, CG
Subject-oriented color rendering
Output Referred
Output device-based color rendering

Although this concept of image state wasborn from within the International
Standardization Committee ISO/TC 42(Photography), it is also extremely valid
when connecting with other devices andtransferring image data.
Furthermore, when attempting to achieve
optimum color reproduction of images
received through various interfaces, theoptions in terms of foundational standardsare:
1. Subject color
2. Remembered color
3. Pleasant color.

50

Fig. 7.28. Gamut mapping.
As a consequence, a color such as Point A
in Fig. 7.28 would be saturated at Point A2C
in sRGB, and even in Adobe RGB it would
be saturated at Point A1C, while in the caseof Adobe RGB, for example, the color
difference between Point A and Point A1C
would not be able to be expressed. In order to

National Museum of Nature and Science Technology Systematization Survey Report

Vol.10 2008. Marchavoid this, gamut mapping is carried via
mathematical color conversion (for example
Point A would be moved to Point A1 in
Adobe RGB, and point A2 in sRGB).
Figure 7.29 shows the image processing
flow that happens in DSCs in accordancewith ISO 17321.
Image sensor output passes through theA/D converter and becomes raw data
possessing the characteristics of the image
sensor. After this raw data is corrected interms of exposure, white balance and image
sensorcharacterizationcompensation,
scene-referred editing is carried out.

As it is unknown what device the data will
be output with, data is processed up to thispoint on the input side with no regard forwhat the output will be, which is known as
scene-referred editing.
In the case of paper scanners and computer
graphics, this is called original-referred
editing, and together they are known as
input-referred editing.
Data that has been through this process ispassed through color rendering, where things
such as tonality correction are carried out by
PCs, etc.

Fig. 7.29. Image processing flowchart.

Systematic Survey on Digital Still Cameras

51

Notes.
[1], [2] From CIPA statistics.
[3]
Provided by Masafumi Inuiya of
Fujifilm.
[4], [5] “Development of a Wide Dynamic
Range Image Sensor for SLR, Super
CCD SR II,” Fujifilm Research andDevelopment, No. 50, 2005.
(provided by Masafumi Inuiya) and“Design Rule for Camera File
System,” Standard of Japan
Electronics and Information
Technology Industries Association
CP-3461.
[6]
From a Sigma press releases.
[7], [8], [9], [10], [11]F. Masuoka, “Rapidly-Advancing
Flash Memory,” Kogyo Chosakai
Publishing Co., Ltd.
[12]The Japan Electronic Industries
Development Association (JEIDA)
merged with the Electronic
Industries Association of Japan(EIAJ) to form the Japan

52

Electronics and Information
Technology Industries Association(JEITA).
[13]
Personal Computer Memory Card
International Association[14]“Fine Imaging and Digital
Photography,” Corona PublishingCo., Ltd., p. 174.
[15]
“Fine Imaging and Digital
Photography,” Corona PublishingCo., Ltd., p. 190“Guidelines for Physics, Electricity,
Physical Formats, Logical Formats,Interface Design” and “Guidelines
for Voltage Capacity Notation,” inSmartMedia specifications (SSFDC
Forum Publishing, 1999 Edition).
[16]“Fine Imaging and Digital
Photography,” Corona PublishingCo., Ltd., p. 180.
[17], [18], [19], [20], [21]“Color Engineering,” Tokyo Denki
University Press.

National Museum of Nature and Science Technology Systematization Survey Report

Vol.10 2008. March

8 Image Compression and Formats
8.1 Image Compression and JPEG
A simple calculation of the output data
volume from a DSC with a 1MP image
sensor where the output from each cell is 1
byte shows that it is 1MB. This means that
only about 64 images can be recorded on a
64MB card. As there was a great demand to
be able to record more images on memory
cards with limited storage capacity, in
response, methods of efficiently reducing
image data volume with minimum
deterioration in image quality weredeveloped.
Image compression methods include spatial
compression, temporal compression andentropy compression. Of these, spatial
compression and entropy compression areused in DSCs for handling still images. In
early DSCs, ADPCM, which is a form ofentropy compression, was employed. Using
the fact that there is little difference between
signals from adjacent pixels, after digitizing
each pixel, the signal for a third pixel ispredicted on the basis of the signals from thefirst and second pixels and the difference
between the actual and predicted signals is
used.
Other compression methods that have been
considered for still images include cosign
transform (DCT for digital), which is a typeof Fourier transform that breaks up data into
spatial frequency components, wavelet
transform (localized Fourier transform) andfractal transform, which breaks up data into
cyclic patterns. Furthermore, entropy
compression,which
minimizes
theredundancy of data after encoding, is anefficient means of improving communication
and recording efficiency.
In 1986, with the aim of internationallystandardizing image compression methods,
ISO TC7 SC2 WG8 and the International

Telegram and Telephone Consultative
Committee (CCITT) SC VIII were combined
to form the Joint Photographic Experts Group(JPEG) under ISO/IEC JTC1 SC2 WG8.
Initially, although there was fierce debate
regarding the DCT method proposed by
Europe, the Vector Quantization (VQ)
method proposed by Japan and the arithmeticcoding proposed by the US, it was Hiroshi
Yasuda of the NTT Musashino Central
Research Center, who was the chairman of
WG8 at the time, who resolved the issue.
Under the direction of Mr. Yasuda, the still
image
compression
format(DigitalCompression
andCodingofContinuous-Tone Still Images) was created in
1992 and introduced in 1994 as ISO 10918-1,
taking on the name of the group that created
it: JPEG. This group is currently engaged inworking on JPEG 2000 and JPEG XR as
ISO/IEC JTC1 SC29 WG1.
Lossless(Spatial prediction encoding)

Used by
Exif
JPEG
FormatOriginal image quality iscompletely maintained

Baseline
Lossy(DCT Format)
Extended
Original image quality is notcompletely maintained

Fig. 8.1. JPEG structure.
As shown in Fig. 8.1, JPEG uses spatial
prediction, which is lossless and makes
lossless compression possible by means ofspatial prediction encoding, and DCT
encoding, which is lossy and uses Adaptive
Discrete Cosine Transform (ADCT) to
analyze spatial frequencies and encode image
data, in combination with entropy
compression.
With the lossless method, although if data
is restored after compression then it ispossible to recreate the original image quality,
Systematic Survey on Digital Still Cameras53

it is not possible to increase the compression
ratio. On the other hand, with the lossy
method, although part of the data from theoriginal image will be lost due tocompression, it is possible to carry out image
compression of 10:1 or more without any real
deterioration in image quality.
Table 8.1. JPEG baseline and extended
methods

amount of data and if it were to be decoded as
it is, then it could be recreated with nodeterioration in the quality of the source
image.
This DCT coefficient is shown in Fig. 8.3.
The coefficient in the top left (0, 0) is the DC
component, while the coefficient in thebottom right is the high-frequency component.
DCT characteristics include the concentrationof components in the low-frequency domain,
and as human visual characteristics include a
reduction in sensitivity in the high-frequency
domain, the importance of the DCT
coefficient therefore drops as it goes from the
top left to the bottom right.

Y direction degree

Depending on the number of bits, the modeand the encoding method used, as shown in
Table 8.1, this lossy compression method canbe divided into baseline and extended types.
The baseline type was used in consumer
DSCs. A block diagram of the coder in the
DCT coding used in JPEG is shown in Fig.
8.2.
8×8 pixel blocks

X direction degree.

EncoderQuantizer

Entropy
Encoder

Table

Table

Compressed
Image Data

Source Image data

Luminance signal quantization
table

Color difference signal
quantization table

Fig. 8.2. DCT encoder block diagram.
In the encoder, input image data is broken
up into 8×8 pixel blocks and each block istransformed by a DCT operation.
DCT is a type of cosine transform carriedout with regard to symmetrical samples in the
Fourier transform that handles discrete
sampling points. This transforms the image,which was a 2D spatial function, into a 2D
frequency function with an 8×8 coefficient.
At that point, there is no reduction in the54

Fig. 8.3. DCT coefficients and zigzag scan.
That is to say, when reading thecoefficients in a zigzag pattern from the upper
left to the bottom right, as shown in Fig. 8.3,
data volume can be reduced as precision is
reduced towards the bottom right, and evenwith compression of 10:1 or more there islittle deterioration in image quality.
With DCT encoding for JPEGs there arequantization tables for both luminance andcolor difference and division is carried out
using the numerical values in the tables
according to each coefficient.
The quantized coefficients are then passed
to an entropy encoding procedure called a
Huffman coding, which compresses the databy assigning a short code to numerals that
occur with a high frequency. Although it ispossible to use default values as quantizationtable values, generally, they are included in

National Museum of Nature and Science Technology Systematization Survey Report

No.10 2008. Marchthe image file together with theentropy-encoding table.
With JPEG, as input image data is broken
up into 8×8 pixel blocks and each block istransformed by the forward DCT, if thecompression ratio is set too high (i.e. thenumber of bits per pixel is reduced) then theboundary line between neighboring blocks
can stand out, which is a phenomenon known
as block noise. Incidentally, the block noise
reduction effect is emphasized in JPEG2000,
which uses wavelet transform, and JPEG XR,
which uses 2D DCT.

8.2 The Necessity of FormattingWith silver halide cameras, although it ispossible to directly view an image after it has
been taken by developing the film, an image
taken using a DSCs is an arrangement of
encoded logical values and unless the
structure of the encoding is understood, it is
impossible to decode the logical value andread the data as a physical quantity, meaningthat it is impossible to playback the image.
Therefore, there must be agreement
regarding the metadata contained in theimage file, for example the color space,which is the coordinates for describing color
information, and common rules regarding thestructure of such metadata must be
determined.
In addition to this kind of image data,
shooting conditions, such as creation
date/time, shutter speed and comments, etc.,
are appended as metadata, which together
comprise what is called the “image file.” In a
broad sense, what dictates the structural
conditions of the image file is the format.
In other words, the types of data recordedin the file, the structure of each type of data
recorded, methods of identifying each kind ofdata, the file format and the file recording
method – everything – is required as
structural elements of the format.
Data is recorded as a digital signal and inorder to recreate it as data, an optimal andcommon format for such data processing isessential.
When discussing formats, it is convenient
to cite the Open Systems Interconnection(OSI) 7-stage model shown in Table 8.2.
Table 8.2. The 7 layers of the OSI model
Upper
LayersLower
LayersApplication
layer
Presentation
layer
Session layer

Controls data
semantic content
Controls data
expression format
Controls dialog units
Controls data transfer
Transport layer
between systems
Network layer Controls networking
Controls transfer
Data link layer
errorsControls
Physical layer electrical/physicalproperties of the line

By defining the protocols used whentransferring data during interconnection andthe content of transferred data in layers inaccordance with this model, it is possible tospecify the transfer methods used when
delivering data. This concept was introduced
by Japan during deliberations at the ISO andas it was useful in defining the object of suchdeliberations it was incorporated into ISO
12234. This 7-level OSI model is shown in
Table 8.2. These levels consist of the upper
three layers that are not recording
media-reliant and the lower four layers thatare recording media-reliant. Control of eachlayer is defined by the content of the layer
beneath it.
These layers in the DSC format can be
defined from the layers beneath as follows:
1. The physical layer: recording media.
2. Controls reading from/writing to therecording media.
3. Determines how image files, including
images and other data, are handled.
4. Determines image file structure.
5. Determines the description format forrecording various types of data.
6. Determines how various data is createdin the image file.
Systematic Survey on Digital Still Cameras55

By determining the definition of each ofthese layers it is possible to transfer data withno errors.

8.3 Recording Media-Reliant
FormatsDiscussions regarding recording media andformats were carried out in the DSC Ad-Hoc
Working Group (WG) that was established in
JEIDA's PC Technology Committee in 1990
and in addition to almost all of the Japanese
domestic
cameramanufacturers
andelectronic device manufacturers, there wasalso much interest from the US.
With the initial DSC format, the main
objective was to determine a method forrecording images as digital signals on
designated recording media, there was no
notion of a format that was not reliant onrecording media and there was no concept ofany detailed developmental direction forhandling IT devices that used digitalcharacteristics.
In the JEIDA DSC Ad-Hoc WG, work
proceeded on the standardization of a format
for both 20-pin and 68-pin cards, which were
the remaining options in terms of PC cards, in
specially established 20-pin and 68-pin
subworking groups (SWGs).
Due to the small number of pins in 20-pin
cards especially, there were plans to makethem the main type of memory cards for use
with DSCs, taking advantage of the fact thatit took much less effort to install and remove
them than with 68-pin cards.
The format for a 20-pin card is shown in
Table 8.3.
Table 8.3. 20-pin card format
#
1
2
3
4
5
6
7

56

Symbol
GND
D0
D1
D2
D3
D4
D5

I/O
–
I/O
I/O
I/O
I/O
I/O
I/O

Meaning
GroundBidirectional data bus”Ditto
Ditto
Ditto
Ditto
Ditto

8
9
10
11
12
13
14
15
16
17
18
19
20

D6
I/O
D7
I/O
Vcc
–
(Vpp)
–
RDY/BSY O
CE
I
A/D
I
R/W
I
BCK
I
RFU
NC
RFU
NC
RFU
NC
GND
–

Ditto
Ditto
Supply voltage
Programing supply voltage
Ready signal
Card enable
Address/Data
Read/Write
Bus ClockReserved for Future Use*
Reserved for Future Use*
Reserved for Future Use*
GroundThis 20-pin card format had the following
characteristics:
a. The card had an I/O bus interface andwas compliant with the I/O bus IC card
standard determined under the JEIDA
guidelines.
b. There were 20 pins. According to the
JEIDA standard the thickness of theedge of 20-pin cards was to be 2.2mm(a maximum of 5 mm was permitted in
the central part), but with these memory
cards the thickness was 2.2 mm overthe entire length of the card.
c. Images, sound and other data were allhandled as separate packets.
d. The cluster method was employed as
the packet recording method.
e. The size of one cluster was 8 KB.
As can be seen from the above, this format
was used to control the read and write
operations and was designed with the
expectation of handling data such as images,
sound and other data, with no detailed image
format being specified.
In early DSCs, image data was digitizedwith 8-bits per NTSC scanning line [3] andused the ADPCM format, which recorded thedifference between predicted and actual
values.
Although the format was determined withthe expectation that 20-pin cards would be
used in the first DSCs, in the end, after
discussions, JEIDA and PCMCIA settled on
68-pin cards and PCMCIA strongly

National Museum of Nature and Science Technology Systematization Survey Report

No.10 2008. Marchdemanded the removal of 20-pin cards fromthe market in order to avoid confusion among
consumers. Therefore, discussions regarding
formats at JEIDA then came to center around68-pin cards and no consumer DSCs using
20-pin cards were ever released.
The format for a 68-pin card is shown in
Table 8.4. This format used a logical memory
allocation table (MAT) formed on thephysical format of the PC card.
Table 8.4. 68-pin card format
00h
01 h
02h
03h-05h06h
07h
08h-17h18h-1Fh20h
21h-25h26h27h28h29h-2Fhn-1nTuple ID[90h]Pointer to next tuple
Scanning method
Image mode
Bits per pixel
Gamma characteristics
Signal level
Number of pixels
Reserved [00h]Screen/pixel aspect ratio
Encoding method
Compression ratio
Uncompressed data recording
mode
Reserved [00000000000000h]
Empty
Next tuple

On the other hand, the various DSC
manufacturers developed proprietary memory
cards other than PC card and DSCs that used
proprietary memory card formats and began
to release them into the market. In otherwords, other than the Still Image, Sound andRelated Information Format (SISRIF), which
was used by PC cards, various proprietary
formats were used: SM cards used Exif, CF
cards used the Camera Image File Format(CIFF) and MemorySticks used the Universal
Disk Format (UDF). Furthermore, theAuto-Indexing Mass Storage (AIMS) card,
which was a memory card for computers, wasproposed by the US, which gave theimpression that the situation could develop
into the kind of format wars that occurred

between VHS and Betamax in the video taperecorder market.
In order to overcome this situation, the
JEIDA committee called for a “format notreliant on recording media” and decided toseparate themselves from discussions
regarding recording media and sought tounify the individual formats that alreadyexisted.

8.4 Formats Not Reliant on
Recording Media
While details regarding coding and datacompression methods are determined within
JPEG, which was established as a standard by
JTC1 (the international standardization
subcommittee for programming languages,
their environments and system softwareinterfaces, which is an ISO/IEC joint
technical
committee),protocolsfortransferring and recording image data are notdetermined. Generally, the JPEG File
Interchange Format (JFIF) is used whenrecording images as JPEGs.
JFIF
wasproposedby
C-CubeMicrosystems in 1991 and uses afile-exchange protocol that is specific to the
JPEG compression format, which was
released as v1.02 in 1992 and can be
identified by the fact that JFIF is noted inapplication segment 0 (App0) in the JPEG
file. JFIF contains formatting rules for image
data files containing compressed image data
and metadata. For example, although there
are no stipulations regarding colors to be usedin JPEG, they can be stipulated in JFIF.
On the other hand, the Tagged Image File
Format (TIFF), which was created in 1986 by
Aldus (now Adobe Systems) and Microsoft
initially for handling images from scanners, isa format for consolidating and storing
different types of image data created using
different specifications into a single file (Fig.
8.4).

Systematic Survey on Digital Still Cameras

57

(Compressed image data)

Metadata

Compressed/uncompressed image data fileFig. 8.4. JPEG, JFIF, TIFF relationship.
With TIFF, the metadata within image files
is treated as packages, with tags being
assigned to show the content of each package.
While JFIF only deals with JPEG files,
TIFF can handle image files that were createdin formats other than JPEG. However, it was
not able to handle compressed images until
TIFF 6.0 was released in 1992.
JFIF and TIFF are both logical concepts
that are not reliant on recording media orsystem and are, I believe, suitable formats foruse with digital content.

8.5 Exif
In order to create the kind of multipurpose
DSC format that is not reliant on recording
media and which is essential for the
popularization of DSCs, it is necessary to
decide on the following control formats thatare defined in the lower layers of the OSImodel.
1. The types of image data that will behandled as image files and their filestructure.
2. The description format for each type ofdata recorded, such as tag format andExtensible Markup Language (XML)format.
3. Methods of creating each type of data
within the file, such as compression
methods for images and audio, coding
methods and the color space employed.
Although in the new format the aim was tohandle both compressed and uncompressed
image files, when handling compressed
image files, with consumer models especially,in order to ensure the popularization of any
new format it is necessary to employ image

58

file compression methods with little
degradation in image quality.
In light of these things, the JEIDA
committee obtained information regarding theJPEG standard before it was officiallyreleased and began to consider the matter.
As shown in Fig. 8.1, JPEG includes
lossless compression, which completely
preserves the original image quality, andlossy compression, which, while it does notpreserve the original quality, makes it
possible to reduce file size.
As a result of their investigations, in 1992,
JEIDA adopted Baseline JPEG format, whichis categorized under lossy compression,ahead of the official announcement of JPEG
as an international standard.
Furthermore, JEIDA negotiated with Adobe
and Microsoft in order to use TIFF as a basefor the image file description format.
However, as compressed images were notable to be handled by TIFF 5.0 at the
beginning of 1992, which was the year inwhich the JEIDA committee created theirdraft proposal, JPEG – JFIF to be more
specific – was used for compressed images,
while uncompressed images and the overall
structure and metadata followed the example
of TIFF.
The image file thus created for DSCs was
newly named Exif and at the same time theitems needing to be defined in the lower
layers of the OSI model were formulated as
Exif R98.
After the basic proposal for Exif had beenformulated, in June 1992, TIFF was revised
to include support for JPEG (TIFF Revision6.0), based on which the US made acounterproposal to Exif to the ISO in theform of TIFF/EP.
As the structure of both of these
specifications was basically the same, after
internal discussions at the ISO it was decided
that interoperability should be maintained
between both specifications by using thesame tags and that Exif would be used for
consumer use while TIFF/EP would be used
for professional use.

National Museum of Nature and Science Technology Systematization Survey Report

No.10 2008. MarchPresently, TIFF/EP has been established as
ISO 12234 Part 2 and Exif has been approved
as a JEITA specification in ISO 12234 Part 1.
At the time that Exif was formulated as a
unified standard that is not reliant onrecording media, fortunately the DSC market
was still small, meaning that the loss sufferedby each company by conceding to change tothe new format was comparatively small. On
the other hand, the advantage of introducing aunified standard was recognized through thework of the technicians on the JEIDA
committee and came to be understood byeach of the different companies.
The US proposed the establishment of a
new working group in ISO TC42
(Photography) to deliberate on standards
regarding DSCs, a proposal that wasapproved by a majority vote. Consequently,
in September 1991, WG18 (Electronic Still
Picture Imaging) was formed, with initialprojects focusing on ISO exposure index,
resolution
testtargets,
definitions/terminology and memory cards.
In light of this, Japanese Industrial
Standards Committee (JISC) instructed that
the JEIDA working group was to handle ISO
discussions regarding formats and at the firstmeeting of WG18 in February 1992 in Las
Vegas the JEIDA specification was proposed.
So, the DSC file format was born out of
discussions regarding the formation of the
JEIDA specification in Japan and was
proposed as an international standard at the
ISO to actually become the Exif global
unified standard for consumer DSCs.
At the same time, a PC card format thatwas not reliant on recording media wasseparately proposed to the ISO and approved
as the SISRIF international standard for PC
cards.
As we can see from Fig. 8.5, the basic
structure of Exif consists of a header, a data
file containing related information, such asshooting conditions and audio, etc., a
thumbnail image containing compressed
image data and an image file containing
image data.

In Exif, which uses the structure of TIFF,
the physical values stored in the image fileare each assigned a tag as individual
metadata.
For each of the metadata that express thedata content, metadata determined in TIFF
uses the TIFF tags just as they, whilenecessary metadata that is unique to DSCs
uses newly added tags.
Detailed tag structure and arrangement
differs according to whether or not a file iscompressed. Exif compressed file structure isshown in Fig. 8.6. In compressed files, theJPEG Application Marker Segment (App)contains an Exif marker with Exif metadata in
App1 and a FlashPix-compatible marker inApp2 by which they can be recognized as
Exif-compatible files.
HeaderNumber of pixels
Compression mode
Creation date/time
Camera model
Aperture
Color space…

Thumbnail image

Main image data

Fig. 8.5. Exif basic structure.

Fig. 8.6. Exif compressed file structure.

Systematic Survey on Digital Still Cameras

59

Table 8.5. Exif tag example
Class Field Name

Fig. 8.7 Exif uncompressed file structure.
On the other hand, with uncompressed files,
as shown in Fig. 8.7, the basic structure of
TIFF is retained.
Some of the tags used in Exif are shown in
Table 8.5. Each tag represents certain
metadata and there are three levels of tags: M(Mandatory), R (Recommended) and O(Optional). The recording function of DSCs
must support all M tags.
As an interchangeable image file format,
Exif has characteristics such as the following:
1. It can handle both compressed anduncompressed image files.
2. It has a tag structure (a common
numbering structure is used to show thecontent of each individual chunk).
3. It can be used in combination with DCF
image format handling rules.
4. It is basically aimed at consumer DSCs.
5. If it is only a matter of viewing images,
then they can be viewed as JPEG. If an
Exif-compatible device or software isused, then it is possible to view Exif data
and Exif metadata, and even after
resaving after retouching Exif data is not
lost.
In addition to image data, Exif contains
various kinds of data regarding shooting
conditions that was unable to be recordedwith silver halide cameras, such as tags
regarding Global Positioning System (GPS)data that show where a photograph was taken,
as well as tags for recording audio and video.
This shows that DSCs are not simply
devices for recording images, but have aplace as information terminal devices.

60

Tag name

Tag
ID

A. Tags relating to image data structure
Image width
256
ImageWidth
ImageLength
Image height
257
Number of bits per
258
BitsPerSample
component
Compression
Compression scheme 259
PhotometricInterp
Pixel composition
262
retation
Orientation
Orientation of image 274
SamplesPerPixel Number of components 277
PlanarConfigurati Image data284
onarrangement
YCbCrSubSampli Subsampling ratio of Y
530
ng
to C
YCbCrPositionin
Y and C positioning
531
g
Image resolution in
XResolution
282
width direction
Image resolution in
YResolution
283
height direction
Unit of X and Y
ResolutionUnit
296
resolution
B. Tags relating to recording offset
StripOffsets
Image data location
273
Number of rows per
RowsPerStrip
278
strip
Bytes per compressed
StripByteCounts
279
strip
JPEGInterchange
Offset to JPEG SOI
513
FormatJPEGInterchange
Bytes of JPEG data
514
FormatLength
C. Tags relating to image data characteristics
TransferFunction Transfer function
301
White point
318
WhitePoint
chromaticity
PrimaryChromati Chromaticities of319
citiesprimaries
Color space
YCbCrCoefficientransformation matrix 529
ts
coefficients
ReferenceBlackW Pair of black and white532
hitereference values
D. Other Tags
File change date and306
DateTime
time
ImageDescription Image title
270
Image input equipment
Make
271
manufacturer
Image input equipment
272
Model
model
Software
Software used
305
Person who created the315
Artistimage
Copyright
Copyright holder
33432

National Museum of Nature and Science Technology Systematization Survey Report

No.10 2008. March

8.6

DCF

Consumer DSC image files recorded inaccordance with the Exif standard can beplayed back regardless of recording media ifusing devices and software that support Exif.
However, if, for example, the recording
media contains a mixture of image files andother files such as text files, unless rules forhandling such files have been established,
then in some cases when using the same
recording media in other DSCs, errors may
occur, resulting in the deletion of recorded
image files. Therefore, it is preferable thatimage files are recorded in accordance withset rules by the recording device and thatsuch files are played back in accordance withthose same rules.
Although specifications regarding image
files were standardized as Exif based on theold Exif standard, methods of controlling
reading from and writing to such recording
media and protocols regarding methods ofhandling image files including images andother data, especially in light of the fact thatsuch files were not expected to be handled
while mixed with other different files, were
inadequate under Exif R98.
After considering this matter, JEIDA
released DCF, which was a new specification
for handling image files in recording media
based on CIFF and Exif R98 (Fig. 8.8).

and devices where the main function is toplayback the main image, such as printers(Reader 2). Devices such as computers needboth Reader and Writer specifications.
The place of Exif and DCF is shown in Fig.
8.9 and related rules for Reader1 and Reader2
are shown in Table 8.6.
Based on the DCF specification, image files
that are structured in accordance with Exif
can be stored together with shooting data on
removable recording media.
As of the time of writing this document, theJapanese-proposed DCF is also in the processof being approved in the ISO specification
ISO 12234 Part 1.
Table 8.6. Readers and writers under DCF

Reader 1

Reader 2

Main Image Thumbnail

DeviceCan be used
to replace themain image
Optional
when
playback is
impossible.

DSC

Required up
to 1,800 ×
1,200

PrinterNamingStructure Rules

Fig. 8.8. The place of Exif and DCF.
Fig. 8.9. Exif and DCF relationship.
In other words, the upper layers in the OSI
7-layer model came to be handled by Exif
while the lower layers were handled by CIFF.
With DCF, the image recording side, forexample a DSC, is called a Writer, while theimage playback side is called a Reader. On
the Reader side there are devices that do notnecessarily need to playback the main image,such as a DSC monitor display, (Reader 1)

8.7 Exif and DCF Revisions
A preliminary draft of Exif was formulated
by JEIDA in 1992 and after being officiallysubmitted to the ISO as a revised draft in
April 1994, it went through the revision
process shown in Table 8.7 until reaching its
Systematic Survey on Digital Still Cameras

61present form (Version 2.21) in 2003. Carewas taken to ensure that each of theserevisions was backwards compatible and the
major revisions were from Exif 2.1 to Exif
2.2 and from Exif 2.2 to Exif 2.21.
Table 8.7. Exif revision history
1994/4

Proposed by JEIDA

1995

Version 1.0

1997/5

Version 1.1

1997/11 Version 2.0
2000(Addition of optional
metadata.)(FlashPix compatibility, audio
data processing function)

Version 2.1

2001

Version 2.2 (Exif Print)

2003

Version
2.21(DCF 2.0 Compatible withextended color space)

Exif 2.2 was published in 2001 and wasreferred to as “Exif Print.” With Exif Print,
when printing images shot using a compatible
DSC, if the printer is also compatible and has
an automatic image processing function, thenthe image may be printed in such a way that
does not reflect the original intent of thephotographer. Exif 2.2 enabled compatible
DSCs to save more information about animage at the time it was recorded, data that isthen used for reference when the printerautomatically processes the photograph,
resulting in images that more faithfully matchthe original scene.
For example, in terms of exposure modes,
when manual exposure, exposure adjustment
or auto bracketing are used, as there is a highpossibility that the photographer intentionallycontrolled exposure, no correction is carriedout, while with auto exposure, exposure
optimization is carried out.
With white balance, color calibration
correction is only carried out when automatic
processing is being carried out. Furthermore,
flash status is checked and if a flash was used,then overexposure is improved and overall
contrast and background brightness improvedand corrected.
In terms of scene modes (portrait,
landscape or night modes), if portrait mode is62

selected then contrast is optimized while
making adjustments to present the nicest skintones before the photograph is printed. If
landscape mode is selected, then contrast andbrightness are adjusted, color corrected andsaturation adjusted in order to present a
contrasty scene. With night mode, dark areas
are constrained while bright areas areemphasized in order to ensure that prints
faithfully reproduce the intent of thephotographer.
Although DSCs were to use the sRGB color
space as stipulated under IEC 61966-2-1 andthe sRGB color space is compatible with
monitors, the color space recorded by DSCs
is capable of reproducing a wider range ofcolors than the color space of monitors.
Furthermore, as the JPEG image
compression standard used by DSCs uses the
YCC color space, in reality, RGB wasconverted to the YCC color space within
DSCs.
Therefore, from Exif 2.2, sYCC was
defined as the color space (IEC 61966-2-1
Amendment 1). sYCC is mathematicallycalculated from sRGB, making it possible touse a wider color gamut.

Fig. 8.10. sRGB and Adobe RGB color
gamut comparison.
The revision from Exif 2.2 to Exif 2.21 wascarried out when DCF 1.0 was revised to
DCF 2.0.
As DSC functionality improved, although
they came to be used in printing andpublishing, color reproduction using the

National Museum of Nature and Science Technology Systematization Survey Report

No.10 2008. MarchsRGB color space was inadequate. Therefore,
Adobe Photoshop® was generally used for
rendering and there were moves among somecamera manufacturers to incorporate the useof Adobe RGB. A comparison of the color
gamut of sRGB and Adobe RGB is shown in
Fig. 8.10.
However, as existing Readers were not able
to identify Adobe RGB, photographs takenusing the Adobe RGB color space wereplayed back in the sRGB color space,meaning that they were not able to utilize thecapabilities of printers that were able toreproduce the Adobe RGB color space.
Furthermore, even if the colors were able tobe corrected in the printer to reproduce colors
in the Adobe RGB color space, there would
still be a slight difference in terms of color
reproduction for images taken using sRGB
and Adobe RGB.
Therefore, after considering the matter in
2002, CIPA announced DCF2.0, which added
DCF option files that could use Adobe RGB
as an optional DCF color space. Details
regarding the revision from DCF 1.0 to DCF
2.0 are shown in Table 8.8.
Table 8.8. Content of DCF1.0 to DCF2.0
revision
Purpose of
Revision

Revision Content

Details
File names startingwith “_”(underscore)

Interoperability
Ability to
Additional definition Index = ”R03”
also useof DCF optional files
Adobe RGB
Color Space Tag =“Uncalibrated”
Tag showing color
space properties (*)
WriterSpecification Able to record DCF optional files
Revision
Reader 1
Revision

Playback of DCF optional file thumbnails
made mandatory

Reader 2
Revision

Playback of DCF optional files madeoptional

RGB color space by assigning a file namestarting with an under bar as a DCF option
file.
Table 8.9. DCF Reader color reproduction

As shown in Table 8.9, images taken using
the Adobe RGB color space are played backby a DCF 1.0 Reader as sRGB while they canbe played back as Adobe RGB color space byReaders that support DCF 2.0.
As Exif and DCF are complementary, withthe revision of DCF to 2.0 Exif was revised
from Version 2.2 to Version 2.21. Details
regarding that revision are shown in Table
8.10.
Both Exif and DCF were considered asinternational standards by the ISO, with Exifbeing approved as ISO 12234-1 while DCF iscurrently in the process of being approved.
However, while it could be said that ingeneral Adobe RGB is becoming more
popular, as it is a Proprietary Standard
determined by a single company, it is unable
to be incorporated in international standards.
Therefore, the IEC sought to establish a new
standard called opRGB (IEC 61966-2-5) on
the basis of content disclosed by Adobe.
Although this was formally released after
Adobe submitted Adobe RGB to theInternational Colour Consortium (ICC) in2006, Adobe still retains the copyright. So,
while it would be good for DSCs if support
for Adobe RGB could be integrated in someway into international standards, just how thatcan be achieved is something that is currently
being worked on by the IEC and ISO.

*Color space characteristics: White point, three primarycolors, YCbCr properties, γ.

In DCF 2.0, facility was made to be able toidentify photographs taken using the Adobe
Systematic Survey on Digital Still Cameras

63

Table 8.10. Exif 2.21 revision details
ExifVersion Tag“2.21”
Gamma Tag
Added
ColorSpace Tag
Definition changed
InterOperabilityInde
Permissible value added
x Tag
Flash Tag
Definition changed
FileSource Tag
Permissible value added
TransferFunction
Levels recorded changed
Pixel composition and
Description Added
image sampling description

In addition to revising Exif and DCF to
make them compatible with Exif 2.2 (ExifPrint) and Adobe RGB, various consortium
standards and industry standards were also
formulated, such as Digital Print Order
Format (DPOF) and PictBridge, which were
auxiliary rules for printing.
DPOF was a consortium standard createdby Canon, Eastman Kodak, Fujifilm andPanasonic to enable digital devices
compatible with DPOF to:a. Designate the frames, number of copies
and to include the date when printing;b. Automatically print as designatedmerely by inserting a memory card into64

a home printer;c. Order prints from a shop without theneed to enter on an order form details
such as the frames and number of prints
to be printed.
PictBridge was proposed by Canon,
Fujifilm, HP, Olympus, Seiko Epson andSony as a direct printing compatible standard
for directly printing images from a DSC
without the need to use a computer, and wasannounced as a CIPA standard (CIPA
DC-001-2003) in February 2003.
Up until that time, when directly printing
DSC images, only dedicated or specificprinters were compatible, but with a
PictBridge-compatible DSC it became
possible to connect any printer, regardless of
make or type.
Notes:[1] “New MPEG Textbook,” ASCII MediaWorks, p. 57.
[2] Compiled from OSI, Japan Standards
Association.
[3] NTSC: National Television Standard
Committee.

National Museum of Nature and Science Technology Systematization Survey Report

No.10 2008. March

9 Standardization of DSCs
9.1

ISO Activities

The international standardization of DSCs
is carried out by the ISO/TC42 (Photography)
committee. The scope of TC 42 is:Standardization primarily, but not exclusively
in the field of still picture imaging – chemicaland electronic – including, but not limited to: definitions for still imaging systems;
 methods for measuring, testing, rating,packaging, labeling, specifying andclassifying the dimensions, physicalproperties
andperformance
characteristics of media, materials anddevices used in chemical and electronic
still imaging; specifications and recommendations oflogical and physical characteristics,
practices, interfaces and formats forstill imaging capture, processing andoutput systems; and methods, measurements, specifications
and recommended practices for storage,
permanence, integrity and security ofimaging media and materials, andimaging materials disposition.
Of those items handled by TC42, although
the following are handled by other ISO TCs
or IEC and JTC1, there is mutual
collaboration between these groups.
 Equipment and systems in the field ofaudio,
video
andaudio-visualengineering (IEC/TC130)
 Cinematography (ISO/TC36)
 Graphic technology (ISO/TC130)
 Document
imaging
applications(ISO/TC171)
 Officeequipment(ISO/IEC
JTC1/SC28)
 Physical keeping of documents(ISO/TC46/SC10)
The following working groups (WGs) andjoint working groups (JWGs) exist within
ISO/TC42.
WG 2
Photoflash units (dormant)
WG 3
Image measurement, viewing andsensitometry
WG 4
Mechanicalelements
ofphotographic equipment
WG 5
Physical properties and image
permanenceofphotographic
materials
WG 6
Photographic
chemicals
andprocessing
WG 8
Joint TC 42-TC 6 WG: Imaging
materials - Dimensions
WG 9
Still projectors and transparencies(dormant)
WG 17 TC 42/WG 3-TC 106- FDI(Fédération
DentaireInternationale) JWG
WG 18 Electronic still picture imaging
WG 19 Recyclingofphotographic
materials (dormant)
JWG 20 ISO/TC 42-IEC JWG: Digital stillcamerasWG 21 TC 42-TC 130 JWG: Density
measurements
JWG 22 IEC/TC 100-ISO/TC 42-TC 130
JWG: Colour management
WG 23 TC
42-TC
130-CIE
JWG:
Extended color encodings for
digital image storage, manipulationand interchange
JWG 24 TC 42-TC 130 WG: Revision of
ISO 3664: 200
As DSCs fall under the productclassification of “cameras,” international
standardization was first managed by the ISO.
However, in 2000, a complaint was filed by
the IEC with the ISO-IEC Joint TechnicalAdvisory Board (JTAB), and as a result of
discussions it was decided that: with regard to DSCs and color
reproduction management, when the
Systematic Survey on Digital Still Cameras

65ISO and the IEC are both concerned,
work would be carried out jointly;
 as mentioned above, JWGs managed
by the ISO would handle mattersconcerning DSCs, while joint project
teams (JPTs) managed by the IEC
would manage matters concerning
color reproduction management.
At present, the most active groups are
WG18 and the associated JWGs 20, 22 and23, and formats for DSCs are being reviewed
by WG18 as ISO 12234.
ISO 12234 is comprised of two parts: Thevarious conditions that must be fulfilled by
DSC storage media are specified in Part 1.
Media and recording formats that conform tothese rules are included in the same as shown
below:
Annex A (Informative) Media profile − PC
Card
Annex B (Informative) Image data format –SISRIF ) a format proposed by Japan for the
PC card)Annex C (Informative) Image data format –ExifAnnex D (Informative) Image data format –TIFF/EP
From among these, TIFF/EP, which was
proposed by the US as described in Annex D,
was made an independent standard: ISO
12234 Part 2.
The reason why Exif was included as an
Annex instead of being made an independent
standard was that making it an independent
standard with the ISO would have meant thatthe copyright, etc., would belong to the ISO,and it was feared that revision work would nolonger be able to be carried out by Japanalone.
Furthermore, DCF, which was also
proposed by Japan, is also being reviewed asISO-12234-1 Annex E.
Standardization work being carried out in
connection with ISO/TC 42 WG18 is shownin Table 9.1. From among these, ISO
12234-1 Annexes B, C and E, and ISO
20462-2, were proposed by Japan, whileother standards, including ISO 12231, 12232

66

and 22028, incorporate many Japaneseopinions.
Table 9.1. DSC-related topics considered by
ISO TC42
ISO No.
12231
12232
12233
12234(1-2)
14524
15739
15740
16067(1-2)
17321
20462(l-3)
21550
22028

TopicsSpecialized
terminology

Content
Terminology

Measurement
methods
Resolution
Tools
FormatModel
Measurement
OECF
methods
Measurement
Noise
methods
PTP
Protocols
Measurement
Scanner
methods
Color
Color properties
characterization
Psychophysical Evaluation
evaluation
methods
Measurement
Scanner D range
methods
Expanded color Color
encodings
management
Sensitivity

The domestic council for the ISO in Japanisthe
Photo-sensitizedMaterials
Manufacturers' Association (PMMA), whichis the secretariat for the ISO TC42 Domestic
Council, and within the Technical Committee
is the Digital Image Working Group, which
deliberates on the subject of digital imaging.
Because this Digital Image Working Groupfunctions as a domestic deliberative body forinternational standardization activities, itdeliberates on problems that are not part of
the activities of CIPA. Because of this, CIPA
is the secretariat of the Digital Image Working
Group but remains independent as anorganization.

9.2 CIPA Standards
CIPA is an industry association establishedon July 1, 2002 with the aim of contributing
to the growth of its members who are

National Museum of Nature and Science Technology Systematization Survey Report

No.10 2008. Marchengaged in the development, production, or
sale of digital and silver halide cameras andrelated devices, equipment and software, andhandles problems on behalf of the industry,
such as environmental concerns, and ensures
product compatibility and fair market
competition, while also carrying out
investigative research and informationexchange for further expansion. It is possible
for Japanese branches of foreign corporations
to be members if they come under one ofcategories described above.
One of the business goals of CIPA is to“formulate and promote technical standards
for the compatibility/interconnection ofimaging-related devices,” and within CIPA a
Standardization
Committee
hasbeenestablished that carries out activities
associated with the goal stated above.
However, as CIPA aims for standardizationthat contributes to the expansion of its
member companies, all of the problems
deliberated on at the ISO do not necessarily
become the subject of deliberation at CIPA,
and CIPA undertakes standardization efforts
of its own.
As of November 2007, standards that havebecome CIPA standards (apart from theJapanese Camera Industry Standard (JCIS)
and Digital Camera Graphical Symbols(DSCSG), which were transferred from theJapan Camera Industries Association (JCIA)
that functioned as an industry association forthe camera industry prior to the establishmentof CIPA) include: CIPA DC-001
Digital Photo Solutions for Imaging
Devices (February 3, 2003)
 CIPA DC-002
Standard Procedure for Measuring
Digital
Still
CameraBattery
Consumption (December 17, 2003)
 CIPA DC-003
Resolution Measurement Methods for
Digital Cameras (December 17, 2003)
 CIPA DC-004
Sensitivity of digital cameras (July 27,
2004)



CIPA DC-005“Picture Transfer Protocol” over
TCP/IP networks (November 8, 2005)
There are also other guidelines, such as the“Specification Guideline for Digital Cameras”
and the “Guideline for Noting Digital Camera
Specification in Catalogs.”

9.3

Collaboration with the US I3A

The International Imaging Industry
Association (I3A) is an industry organization
dealing with matters relating to cameras andimaging devices, etc., in the US. Within the
I3A there are working groups called initiative
groups, in addition to a technical committee.
The technical committee is commissioned by
the American National Standards Institute(ANSI), the secretariat of the ISO/TC 42 in
the US, to administer its affairs. For thisreason, businesses may freely participate in
the technical committee while observing thereasonable and non-discriminatory terms(RAND) policy of the ISO with regard to
intellectual property (IP) rights, but initiatives
are contracted research to be carried out by
restricted members and as such their content
is private.
The technical committee of the I3A is theequivalent of the ISO/TC 42 Domestic
Council Technical Committee in Japan, andits position as the secretariat of the technicalcommittee in the USA is the equivalent ofthat of the PMMA (secretariat of the ISO/TC
42 Domestic Council) in Japan. Furthermore,
it could be said, from the similarities in the IP
policy of the initiative groups of the I3A, thatthey are the equivalent of the Standardization
Committee in CIPA.
I3A and CIPA are both internationalorganizations, and as they are industry
associations for manufactures of imaging
devices, a cooperative framework for bothparties has been discussed a number of times
in the past. However, on account ofdifferences in attitude toward IP, although
there is mutual exchange, a cooperative
framework has yet to be established.
Systematic Survey on Digital Still Cameras

67

10 The Future of DSCs
According to a survey of consumer trends
published by Japan's Economic and Social
Research Institute (ESRI), the spread of
DSCs has been rapid (as shown in Fig. 10.1),
and it was reported that they had achieved an
adoption rate in excess of a 60% by 2007 [1].
Moreover, according to the Ministry ofInternal Affairs and Communications, people
own 2.5 color televisions, 1.9 mobile phones,
1.0
personalcomputers,
0.9
DVD
players/recorders, and 0.7 digital cameras perhousehold [2].
(AV/digital devices/passenger vehicles)

Color TVs

Mobile Phones

Passenger Cars

Used Cars
New Cars
Digital Cameras
Video Cameras

DVD Players/Recorders

PCs
Faxes

Fig. 10.1. Ownership of durable consumer
goods.
Although consumer DSCs have achieved asurprising degree of market penetration in the
10 or so years since they were released into
the market, future challenges are alreadyarising.
Legally speaking, DSCs are optical
instruments and like machine tools and clocks
fall under the jurisdiction of the Industrial
Machinery Division of the Ministry of
Economy, Trade and Industry's (METI)
Manufacturing Industries Bureau. However,rather than DSCs being classified simply as a
substitute for their predecessors, silver halide
cameras, they are classified as a kind of
information appliance for creating images aselectronic information.
We will now explore some of the problems(including the abovementioned stance of the
METI) that will need to be considered with68

regard to DSCs in the future.

10.1 The Future of Formats for
DSCs
Ten or more years have already passed
since the establishment of Exif/DCF as a
unified format for consumer DSCs. Although
they underwent several revisions during thattime, the greatest challenge with thoserevisions was to maintain compatibility withprevious versions. Within the camera market,
at a time when DSCs already have an
overwhelming share of the market, theintroduction of new format that breakcompatibility with old versions would
predictably confuse the market and stir
discontent among users, meaning that it
would not be a good policy for manufacturers.
Consequently, in terms of consumer DSCs, itfollows that it is necessary to further evolvethe existing Exif/DCF technology while
preserving backwards compatibility.
On the other hand, it is true that some(including the US) say that developing newtechnology and introducing new formats
rather than maintaining compatibility with
Exif/DCF would be good for both theindustry and consumers.
One of the main challenges that frequency
comes up is the issue of formats.
10-1-1 Color Space Considerations
The revision of DCF 1.0 to DCF 2.0 and
Exif 2.2 to 2.21 was due to requests for
expansion of the color gamut.
Color spaces are classified into input- andoutput-referred color spaces. Input-referredcolor spaces are color spaces for
input-referred image data, such as from actual
scenes, computer-simulated scenes andscanners, and include RAW data and silver
halide negative film, both of which have a

National Museum of Nature and Science Technology Systematization Survey Report

No.10 2008. Marchwide dynamic range.
On the other hand, output-referred color
spaces are for recording data processed forspecific purposes (monitors, printers, etc.),
and include DSCs in general and reversal
film.
Table 10.1. Various color spaces
ROMM RIMM Adobe
RGB
RGB
RGB
Output Extended Output
OutputReferred
Scene
CRT
OutputPrint
Print
0.64000.73470.6400R:x.y
0.33000.26530.33000.30000.15960.2100G:x,y0.60000.84040.71000.15000.03660.1500B:x,y
0.06000.00010.0600
IEC6196 ANSI/I3 ANSI/13 Adobe
IEC6196
6-2-1
A-IT10 A-IT10 RGB
6-2-1
Amend1 7666
7466
(ICC)
sRGB

sYCC

The various color spaces used in DSCs areshown in Fig. 10.1. Among these is a format
proposed by the US to the ISO and which (asa result of deliberation) became RIMM-RGB(ANSI/I3A-IT10.7466), which describes ascene-referred (a form of input-referred) color
space. Research is currently being carried out
in the US with a view to introducing RIMM
RGB and Camera RAW file format
compatibility (described below) into theformat.
Furthermore, the handling of not only thethree primary colors (RGB), but also manycolors, and ultimately colors as a spectrum isalso being considered, but specific proposals
have yet to be presented. It is hoped thatinteracting with the printing industry, whichtakes multicolor as a given, will stimulate
research in this field.
10-1-2 Camera RAW Image Data
Figure 7.3 shows the average unit price of
DSCs by pixel resolution, but while the unit
price of DSCs with equal pixel resolution
decreases, increases in pixel resolution enablemodels to be marketed as higher-grade
products, and it can be seen that as thisprocess repeats, the expansion of the market
as a whole is maintained (from CIPA

statistics).
According to recent CIPA statistics, as canbe seem in Fig. 10.2, the proportion of the
DSC market occupied by SLR cameras isincreasing, reaching about 10% in terms ofthe number of units sold and exceeding 20%
in terms of value. Nearly all of these SLRs
have their own RAW image data output
format.

Units
Value

Fig. 10.2. D-SLR trends.
DSC RAW image data is “raw” data
generated by the DSC's sensor that has notundergone image processing.
Not included in this definition of image
processing are A/D conversion, linearization,
dark current and frame removal, shading andsensitivity (linear domain) compensation,
flare removal, white balance, and restorationof missing pixels. Because RAW Image Data
preserves high image quality, processing
images afterwards is easy, meaning that thisformat is preferred by photographers andpublishers, etc.
However, file formats differ according to
make and model without any unified standard,
and the specifications are the know-how ofthe various manufacturers.
For example, RAW image data differs
according to image pickup device,configuration, number of pixels andchromaticity, etc. Examples of image pickup
devices used for SLRs are shown in Table
10.2.
On account of this, companies must prepare
Systematic Survey on Digital Still Cameras69

an extension that uniquely identifies their
RAW images and software that is compatible
with them. Examples of extensions that
identify RAW image files are shown in Table
10.3.
Table 10.2. Examples of image sensors for
SLRs

Table 10.3. Examples of extension names
Type
Nikon
PENTAX
MinoltaOlympusFujifilm
SONY
EPSON
Adobe Digital
Negative
Canon

DNG
CR2
CRW
X3F
DRF

CIFF
Original
Image

Proprietary
FormatProvisions to handle these RAW image
files are not included in the current Exif/DCF
standards. Consequently, either formats thatcover beyond the stipulated range of
Exif/DCF, such as TIFF or TIFF/EP, or
proprietary formats are used.
As it is difficult to handle these in a unified
manner, at present even Adobe Digital
Negative (DNG) and Windows Vista, whichclaim to be able to handle RAW image data,
use plug-ins with the format in which RAW
image data is recorded to handle such images.
Although there are moves to support RAW
under TIFF/EP, investigation is still70

10-1-3 Compression Methods
The JPEG image compression algorithm
adopted with Exif performs DCT within 8×8
blocks of pixels that have 8-bits per pixel
before carrying out spatial compression, andthen performs further compression of code
length using Huffman coding (a form ofentropy coding). The mathematics of thiscompression algorithm is simple and thedeterioration in picture quality with acompression ratio of up to 10:1 is almost
imperceptible.
However, there are concerns that increasing
the compression ratio will cause blocking
artifacts (where the boundaries of the 8×8
blocks becomes obvious), and that
corporations with patent claims pertaining to
Huffman coding may appear.
JPEG was adopted as a standard by
ISO/IEC JTC 1/SC 29, followed by JPEG
2000 in January 2001. The discrete wavelet
transform (DWT) used by JPEG 2000 in its
image compression algorithm is shown in Fig.
8.3.

Vertical

SIGMA
ProBack

Extension File Format
NEF
TIFF/EP
PEF
MRW
ORF
RAF
SRF
TIFF
ERF

underway with regard to what conditions
would be required.

Horizontal

Fig. 10.3. The principle of DWT.
While DCT uses a common orthogonal
function to transform the whole image into
spatial frequencies, DWT uses a wavelet,
which is a local orthogonal function that
performs orthogonal transformation as adigital operation.
The spatial frequency values resulting fromthe orthogonal transformation vary according
to their position on the image. In Fig. 10.3, H
represents high spatial frequency components

National Museum of Nature and Science Technology Systematization Survey Report

No.10 2008. Marchand L represents low spatial frequency
components. In this example, LL represents
images composed of low spatial frequency
components vertically and horizontally, andHH represents images composed of highspatial frequency components vertically andhorizontally.
An image comprised only of LL would beentirely blurred, and would become clearer as
the component on the lower right is added toit. JPEG 2000 supports lossless compression,and also has the feature of being able to store
images with differing compression rates
inside the same image file at the same time.

JPEG2000 Lossy
JPEG2000 LosslessFig. 10.4. Compression technology and noise.
According to IEEE Signal Processing
Magazine, although JPEG 2000 is reported to
produce less noise (Fig. 10.4) even underhigh compression, the difference was 2–3 dB.
Complex mathematical operations are notthe only drawback with JPEG 2000;
attempting to include it in Exif/DCF, which
has undergone revision with an emphasis oncompatibility, would present great difficulties
as it is not at all compatible with JPEG.
Although there has been a proposal to create
a new tag to recognize the existence of JPEG
2000 files in order to enable coexistence of
JPEG 2000 and JPEG image files in Exif,
from the perspective of focusing on thefunctions that are sought after in a consumer
DSC, it was thought that realizing this would
be difficult. At this point in time, it is agreed
that the focus should be on providing

standardization of metadata for DSCs.
A comparison of Exif/DCF and JPEG2000
is shown in Table 10.4.
Table 10.4. A comparison of Exif/DCF and
JPEG 2000
Image
Compression
Bits/Pixels
Color Space

8sRGB/Option

Encoding

Huffman

Imagecompression

Lossy

Disadvantages

Maximum
block noise at
highcompression

Complexoperation

Notes

Most popular

LayeredimagesExif/DCF DCT

JPEG 2000
DWT
Up to 32
Not specified
EBCDT(Embedded
Block Coding
withOptimized
Truncation)
Lossy toLossless

10-1-4 Description Formats
Files are described using the TIFF format in
Exif/DCF. The US has proposed describing
them using XML. Although XML and TIFF
are both languages that use tags in a similar
way for description, their formats aredifferent. At this point in time it would be
difficult to change DSC tags to XML, andattempts are being made to standardize
metadata so that it can be adopted as tags.
Furthermore, a proposal to describe ICC
profiles instead of designating a color space
has been presented by the US. ICC profiles
are specifications specified by the ICC. The
proposal is to make color spaces not reliant
on input/output devices by embedding thespecifications of the input device in the formof a profile, describing input images withcolor spaces not reliant on devices (XYZ or
LAB color spaces for example) andcompensating on the output side for the
profile of the output device. A scheme has
been prepared to embed these ICC profiles in
TIFF/EP.
This appears to be more than what is
Systematic Survey on Digital Still Cameras

71required for consumer DSCs and although it
is a fact that current ICC profiles have yet toattain perfect color reproduction, in response
to demands from the printing and publishingindustries for higher image quality,
consideration of such a specification may benecessary.
The strongest attractions of DSCs are theirability to review images immediately and tosimply and without delay print and save a
hard copy of necessary images using a
dedicated or generic printer at home. DSCs
have become the center of the still imaging
industry as an exceedingly convenient andappropriate means for creating image datathat is essential for our modern life, and are
responsible for leading the development of
the entire industry while maintaining
compatibility
withthesurrounding
technological environment.
In the past, printers were treated as officemachines, and it is primarily because of the
popularization of DSCs that they have cometo be used so extensively in the home forprinting photographs. It cannot therefore be
said that compatibility between DSCs andprinters is altogether satisfactory. Revisionsof Exif, DPOF and PictBridge, etc., have thus
far been designed to provide compatibility
between DSCs and printers, but there is no
shortage of problems, such as whether or not
the color gamut of DSCs can be reflected in
the range of colors reproducible by printers,
and whether or not RGB and CMYK color
spaces can be matched, as well as the matterof investigating how to increase color range.
DSCs initially adopted sRGB, a color spacefor CRT displays. DSCs, however, have awider color gamut than displays, althoughconversely it could be said that the color
gamuts of displays have not yet caught up
with those of cameras. For this reason, whenusing the industry standard raster graphics
editor Adobe Photoshop®, as the true colors
are unable to be verified by viewing theactual colors on a computer display, they areverified by checking the displayed RGB
values.

72

However,inrecenttimes,
withimprovements
incomputerdisplaytechnology, displays have been released (byMitsubishi Electric, for example) that can
reproduce the Adobe RGB color gamut.
DSCs in the future will no doubt maintain areciprocal relationship with peripheraldevices as a pivotal device in the image
industry and keep advancing technologically,
while influencing the industries ofsurrounding equipment and expanding themarket.

10.2 Coordination with Other
Industries
With silver halide cameras, all that wasnecessary was to think about how to take andproduce a photograph, which is somewhat ofa narrow perspective. By contrast, however,with DSCs it became necessary to think ofcompatibility with other related fields.
Although such requirements are especially
important with professional DSCs, as there
are not necessarily any precise classifications
separating
consumermodelsfromprofessional products, this could beinterpreted as posing a problem for all DSCs.
10-2-1 Compatibility with IT Equipment
In the beginning, DSCs were developedwith playback of images on TVs in mind, andthe emphasis came to be placed oncompatibility with computers as aconsequence of the spread of computers andthe expansion of the internet. Operating
system developers were contacted for thisreason, and were successfully persuaded tosupportExif/DCF.
With
today's
popularization of DSCs, operating system
support for DSCs is a great advantage forcomputers, and has resulted in a synergistic
effect that has helped the expansion of both.
The connection between DSCs and computers
is expected to grow more intimate as time
progresses.

National Museum of Nature and Science Technology Systematization Survey Report

No.10 2008. March

10-2-2 Printing-related Compatibility
Digitization of printing and the graphics
editing process which precedes printing is
rapidly advancing, and although DSCs arewidely used as image input devices forprinting, it cannot be said that the dynamic
range and reproducible color gamut of
consumer DSCs that conform to Exif/DCF isadequate.
Although the color space first adopted for
DSCs was sRGB (an output-referred color
space based on CRT displays), because DSCs
were capable of capturing a wider color spacethan sRGB, the interpretation of the color
space was changed to sYCC. Furthermore,
support for Adobe RGB was added in Exif
2.21/DCF 2.0 for popular image editing
software such as Adobe Photoshop®.
Although SLR-type DSCs for professionaluse can produce RAW data, this is in order toprovide support for photographic subjects
with a wide dynamic range. For this reason,
the US has proposed the concept of using
input-referred color spaces for RAW data.
The improvement of DSCs based on theexchange of information with the printing
industry is very important when formulating
standards. For this reason, ISO/TC 42, which
deliberates on international standards for
DSCs, has a very close relationship with
ISO/TC 130, which is in charge of graphic
technology, forming a joint working group to

deliberate on color management and related
subjects.
10-2-3 Compatibility with Communication
Devices
In recent years, phones equipped with acamera function (camera phones) havebecome mainstream, but the mobile phoneindustry in Japan is working in a different
field from consumer devices as phones
involve the use of radio waves. However,
because the companies that manufacture
telephones and offer them to carriers overlap
with those manufacturing DSCs, and because
camera phones utilize a considerable amountof DSC technology, making camera
technology the main subject of technicalinvestigation for camera phones is notthought to be impossible.
Camera Phone Image Quality (CPIQ) is
already included in an investigation regarding
image quality as one of the initiatives of the
I3A.
Notes:[1] Consumer behavior study published by
the Department of Business Statistics,
Economic and Social Research Institutein April 2007.
[2] White paper published in 2007 by the
Ministry of Internal Affairs andCommunications: Appendix.

Systematic Survey on Digital Still Cameras

73

11 Discussion and Acknowledgements
Mankind has used images as a means ofcommunication
since
ancient
times.
Communication by means of images is an
excellent method that enables the perceptionof meaning without knowledge of symbolic
constructs such as language and letters. This
excellent means of communication is,furthermore, only used by mankind.
Mankind developed “imaging culture” anddeveloped diverse technical innovations tofurther advance that imaging culture. Imaging
culture led to the formation of cultures known
as the pictorial arts and has left behind manytechnical innovations for their development.
Subsequent
technical
developments
resulted in the development of the camera,
which enabled the easy creation ofsatisfyingly good quality technically difficult
pictures without the need to be technicallyproficient.
The course of camera development can beclassified into technologies that support
cameras as imaging devices and technologies
that support them as IT equipment, as issystematically shown in the attached figures.
The origin of cameras dates back to the 3rd
century B.C. when Aristotle mentioned thecamera obscura.
After the beginning of the 19th century,
images were first successfully made with aphotochemical
reaction.
Subsequently,
ongoing technological reforms made it
possible to take accurate images in a shortertime more easily and cheaply, and as a resultof the development of user-friendly features,such as automatic exposure and autofocus,
photography came to the point where it wassaid that cameras were a must-have status
symbol in postwar Japan.
However, in the latter part of 20th century,
which could be called the electronic age, thecamera appeared to be keeping its place as adevice based on chemical reactions amidst
the computerization of a wide range of daily

74

necessities.
The computerization of imaging devices
began with broadcasting devices. Videocameras and 8 mm camcorders for household
use and other such video devices are
consumer versions of broadcasting level
devices.
These devices nevertheless recorded image
information as analog signals on media suchas magnetic tape or magnetic disks, and it
was not possible to prevent the deteriorationof picture quality when transmitting or
copying.
The Mavica electronic camera, which was
released in 1981, took one frame from a video
camera and recorded it to a floppy disk as astill image. This should be recognized as thefirst commercial device that recorded still
images electronically.
However, even with this electronic camera,
aside from image information, although it
was possible for it to record audio
information at the same time, which wassomething used in a secondary manner as
auxiliary information for the recorded images,
it could not go so far as to record information
regarding when the picture was taken or
related metadata.
Only after the first DSCs appeared wereimages handled as logical information in atrue multimedia-compatible environment.
Digital is outside of human perception, andis a method of logically describing physicalphenomena. The silver halide cameras of thepast obtained latent images with chemical
reactions, but these latent images could bematerialized and viewed without special rules
or arrangements.
By contrast, DSC images are encoded andrecorded according to specified rules, andviewing the image would be impossible
without such rules being made known. Whilecommunication via images began as a meansof directly physically influencing another

National Museum of Nature and Science Technology Systematization Survey Report

No.10 2008. March

party visually, it should be noted that DSCs
rely on a logical means of transmitting andstoring images.
Compared with previous means ofcommunication that transmitted or stored
perceptible physical quantities as they were,with DSCs (apart from the input/output
portion that exerts an influence upon thesenses) all transmission, storage andprocessing, etc., used rational logicalquantities know as digital. It also became
possible to record auxiliary information at thesame time as images according to logicaldescription along with the image information.
On account of such properties, the status of
DSCs is as an image input device inside animage information system, whereas silver
halide cameras were devices for the purposeof taking images.
A great contribution toward the realizationof this was the creation of a format that used
JPEG and TIFF as a base. The advent of flash
memory and the memory cards that used it
also contributed greatly.
The first DSC released into the market cost
about the same as a car after including thecost of the playback device and recording
apparatus, etc., but since 1995, when the
QV-10A was released at a cost of just under¥50,000, the price of DSCs has come down inprice every year while performance hascontinued to improve. The first DSCs in 1989
used CCDs with 400,000 pixels, and fell verymuch short of the resolution of silver halide
cameras, but by 1983, “megapixel” CCDswith over 1,000,000 pixels had been
introduced, and pixel resolution has advanced
year after year ever since.
During the period that the resolution of
DSCs was poor as compared with that ofsilver halide cameras, large-format film was
the mainstay in the printing industry for
posters and publications, etc. Among recent
DSCs, however, there are some that compare
favorably with large-format silver halide
cameras both in terms of resolution and color
reproducibility, and the adoption of digitaltechnology is rapidly increasing in the field ofprinting, with increased technologicalinteraction with DSCs.
Among compact DSCs for consumers aremodels that presently sell for around 10,000
JPY, and personal computers are a significant
reason for the existence of these DSCs.
Operating systems have improved to thepoint that PCs can now process DSC images,
and printer manufacturers have worked
together with DSC manufacturers to makeimage printing from DSCs easier and to
improve functionality.
Moreover, mobile phones achieved rapid
growth as personal data devices, with morethan half of such phone featuring a camera.
These camera phones were also therecipients of technology transfer from DSCs,
and are compatible with images photographedwith DSCs due to the fact that they work withthe same format. Because of this, it could bethought that these phones with cameras could
be placed in the same category as DSCs.
There is, no doubt, a market for camera
phones especially among users who feel thathaving to carry around a DSC in addition to amobile phone is inconvenient, users who aresatisfied with the image quality of camera
phones, and users who send photos that theytake to their friends more often than they savethem.
In the future, DSCs are expected tocontinue to develop as image information
devices. One goal is to split development on
the basis of performance, with models for
professional and high-end amateur users with
an emphasis on high resolution andperformance and compact, easy-to-use DSCs
for consumer use. The other goal is to further
develop camera phones for users who do notwant to carry around a DSC and who aresatisfied with the picture quality of mobile
phones. A three-model solution is thereby
emerging that brings these two goals together.
In closing, I would like to express my deep
gratitude to those who took time to share
information, provide material, and otherwise
assist in the compilation of this report.

Systematic Survey on Digital Still Cameras

75[1] Japan Camera Industry Institute[2] Camera
andImaging
Products
Association (CIPA)[3] Canon, Inc., Image Communication
Products Operations and Public Affairs
Headquarters[4] Fujifilm
Co.,
Ltd.,
Corporate
Communications Office and Masafumi
Inuiya of the Frontier Core-Technology
Laboratories[5] Hiroyuki Suetaka, Casio Hitachi Mobile
Communications Co, Ltd.
[6] Toshiba Science Museum

76[7] Fujio Masuoka, Tohoku University
Professor Emeritus[8] Masayuki Uchiyama, President, Image
Link, Inc.
[9] Shigeharu Ochi, Japanese representativefor InvenSense, formerly of Fuji Photo
Film Co., Ltd.
[10] Toru Takahashi, Vice President, Internet
Association Japan; Founder & Chairman,
Research Institute for Internet Strategies,
Inc.
[11] Masanobu Iseri, President, Impress R&D(In no particular order.)National Museum of Nature and Science Technology Systematization Survey Report

No.10 2008. MarchDSC Genealogy
IT Equipment
Computer Side

Images Side10MPOS Support

Higher image quality
Higher functionality

For Printing

1MP
Exif/DCF Color
Management
Technology

CMOS
Commercialization
0.4MP

First DSCs

DigitalFlash Memory
Memory Cards

Electronic Cameras

Media Use
Electronic

Magnetic Recording

BroadcastEquipment

CamerasImagesPortrait
Replacement

Lens
OpticsChemistry
Gadgets

Communication
using Images

Cave Paintings
Paintings

Systematic Survey on Digital Still Cameras

77Appendix 1. List of significant models
Name

Reference
Type

Digital camera
prototype
Actual
1 DC-90
Unit
Nickname:“Atsuko” (Hot)Digital Camera
Prototype
DC-90
Actual2
Nickname:
Unit“Omoko”(Heavy)EOS
Kiss Actual
3
DIGITAL
Unit

78

4 FUJIX DS-1P

ActualUnit

5 FUJIX DS-X

ActualUnit

6 FinePix 4700

ActualUnit

7 FinePix F700

ActualUnit

Address

Manufactu
rer2-229-1
Sakuragaoka,
Higashi-Yamato
City, Tokyo
Casio Hitachi
MobileCommunications
Co., Ltd.

Casio
ComputerCo., Ltd.

3-30-2
Shimomaruko,
Ohta-ku, Tokyo

Canon,
Inc.

Year

1991

A working prototype created together with “Omoko” (heavy) as a prototype for the QV-10 digital
camera with LCD monitor released by Casio Computer Co., Ltd. in 1995. As this unit produced a
lot of heat it was nicknamed “Atsuko” (hot). As operation would become unstable due to the heatgenerated, the viewfinder was removed and a cooling fan installed in its place and an LCD TV
hooked up and used in place of the viewfinder, which led to the use of LCD monitors in digital
cameras.
A working prototype of the QV-10 created together with “Atsuko” (hot). As this unit was madeusing generic parts, making it heavy, it was nicknamed “Omoko” (heavy).

1991

2003

1988

1990
9-7-3, Akasaka,
Minato-ku, Tokyo(Tokyo Midtown)

Comments

Fujifilm
CorporationNational Museum of Nature and Science Technology Systematization Survey Report

2000

2003

No.10 2008. March

Featuring a large 6.3MP single-plate CMOS sensor (22.7×15.1 mm (APS-C equivalent))
developed by Canon couple with Canon's proprietary high-performance DIGIC image processor,
this model was the company's response to demands by many users for a camera with highresolution, high image quality and natural colors.
After converting light to an electrical signal using a CCD and passing it through an AD
converter, the resulting digital data was saved to a memory card, making this the world's first true
digital camera. It was able to record ten images in field mode and five images in frame mode in asingle 2MB SRAM card. Digital data was read from the memory card to a PC where it wasprocessed. Dimensions: 105 (W) × 75 (H) × 50 ( D) mm, Body weight: 400 g
The world's first commercially-produced and sold digital camera. It could compress (PCM
(ADPCM)) and record up to six images in frame mode on a 2MB SRAM card. Furthermore, its
binocular design diverged from that of traditional film cameras.
This was the first digital camera to use Fujifilm's proprietary Super CCD honeycomb sensor(2.4MP), which improved resolution by arranging octagonal CCD photodiodes in a diamondhoneycomb pattern to optimize light concentration and realize an improved SN ratio to produce
4.32 megapixel images.
Featuring the Super CCD Honeycomb 4SR sensor with its unique pairs of pixels with different
sensitivity (6.2 million pixels: 3.1 million high-sensitivity S pixels and 3.1 million R pixels with awide dynamic range), this digital camera realized a 400% increase in dynamic range overprevious models, and was strongly resistant to white-out and loss of black detail, resulting inimages with smooth graduations from light to dark.

Appendix 2. Chronology
Year

Number of
DSC
PC
Pixels (Unit:
Internet Production
Penetrati
10,000Users (%) (100 millionon (%)
pixels)*JPY)

Details

30,000 B.C. Altamira Cave wall paintings
16,000–8,000
Aristotle, the original form of the camera obscura
B.C.
– 350 B.C.
Ancient Egypt wall paintings
Kitora and Takamatsuzuka tomb paintings, Japan's
2,400 B.C.
oldest portraits (Prince Shotoku)
Late 1600s to
Popularization of the Camera Obscura
early 1700s
Thomas Wedgewood, method of fixing an image using
18th Century
silver nitrate
1802
Nicéphore Niépce, Heliography announced
Oldest existing photograph (Niépce's “Man leading a1824
horse”)
1825
Daguerreotype announced
1839
Talbot, the invention of the negative/positive process
Archer, the invention of the wet-plate photographic
1841
process
1851
Invention of the dry plate photographic process
1871
Eastman Kodak, Camera and film set released
1888
RolleiFlex released
1928
Autofocus
1981
Mavica released
Still Picture Recording Processor using Audio Cassette
1985
Deck announced
1987
World's first DSC prototype DS-1P (Fujifilm)
World's first commercially available DSC DS-X(Fuji
1988
Photo), IMC-100 (Toshiba)
1989
1990
JEIDA digital camera WG formed
1991
ISO TC42 WG18 established, format proposed by Japan
Atsuko and Omoko prototypes (Casio)
Exif standard (JEIDA)
1992
JPEG standard (ISO/IEC JTC1)
1993
VC-1000 (Olympus)
QV-10A (Casio)
1994
Exif proposed to the ISO (JEIDA)1995
QV-10 (Casio) (¥49,800) Exif Version 1
1996
Various companies introduce 0.3–0.8MP DSCs
1997
Exif Version 1.1 /Version2.0
1998
Compact megapixel DSC FinePix700 (Fujifilm)
1999
Rise of DSLRs
Super CCD honeycomb (Fujifilm)
EOS D30 with CMOS sensor equivalent to C-size sensor
2000(Canon)Compact DSC IXY DIGITAL (Canon)
Mobile phone with camera (Sharp J-SH04)
2001
5MP COOLPIX 5000 (Nikon)
2002
FOVEON X3
Super CCD honeycomb 4SR (Fujifilm)
2003
DSLR entry-level model EOS Kiss DIGITAL (Canon)
2004
Exif approved in IOS2234
2005
Adobe DNG
2006
10MP DSLRs
2007
12MP D3 / D300 (Nikon)* Consumer DSCs.

40

11.7
9.7
11.6
10.6
11.5
12.2
11.9
13.9

200

15.6
17.3
22.1
25.2
29.5

9.2
13.4
21.4

300

38.6

37.1

4,257

500

50.1
57.2

44.0
54.5

5,725
6,742

63.3

60.6

10,720

65.7
64.6
68.3
71.0

62.3
66.8
68.5

13,62812,76214.033

100

1000

Historical Development of Digital Still Cameras

79This report contains the results of research titled “A Study about Japanese Innovation Basedon a History of Industrial Technology Document” (17074009) that was carried out as part ofplanned research under “Technological Innovation in Japan: Collecting Experiences andEstablishing Knowledge Foundation,” which was funded by a Japanese government
Grant-in-Aid for Scientific Research on Priority Areas in 2007.

National Museum of Nature and Science: Survey Reportson the Systemization of Technologies Vol. 10
March 19, 2008
 Edited by: Center of the History of Japanese Industrial
Technology, National Museum of Nature and Science(Coordinated and Edited by: Takayuki Nagata, Editedby Toshihiko Okura and Toshio Kubota)
 Published by: National Museum of Nature and Science
7-20 Ueno Koen, Taito-ku, Tokyo 110-8718
TEL: 03-3822-0111
 Designed/Printed by: J-Spark Corporation