Newsgroup: it.arti.fotografia.digitale
Titolo: differenza CCD /CMOS

Salve a tutti,
dovendo munirmi a breve di una reflex digitale vorrei capire bene quali
differenze potrei rilevare osservando una stessa fotografia ma effettuata
con le due diverse tipologie di sensori.
Esiste un settore fotografico per cui l'utilizzo del ccd è preferibile al
Cmos e viceversa?
Vi ringrazio anticipatamente per le vostre risposte.
Saluti a Tutti
Loris

 Cmos e viceversa?
Il CMOS e' in poche parole il CCD dei poveri. Costa poco perche' per
produrlo si possono utilizzare le linee di produzione utilizzate per altri
componenti, pero' hanno la fregatura di aver un piu' elevato rumore di
fondo.
Ergo........molto meglio il ccd.
andrea

Controlla bene le varie reviews delle fotocamere su 
www.dpreview.com
Le parti fra CCD e CMOS si stanno ribaltando e pare che gli ultimi CMOS
siano molto superiori dei CCD.
Infatti iniziano a montarli su macchine ad altissimo livello.
Di certo scaldano e consumano di meno.
Forse è un po presto ma se hai soldi prendi CMOS

 Forse è un po presto ma se hai soldi prendi CMOS
...ti do il consiglio esattamente opposto....prendi CCD ;-))
erik
--------------------------------
Inviato via 
http://usenet.libero.it

 ...ti do il consiglio esattamente opposto....prendi CCD ;-))
Direi di più prendi quello che ti pare.
Comunque odio i Flame,   io mi fermo qui!!
ciao paolo

P.Mattiolo Iw3arv wrote:
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Mi spiace, ma pure io voto x il CCD! Da astrofilo ti dico che come rumore
di fondo e prestazioni non esiste CMOS che si avvicini ad un CCD. Quindi, 
prendi CCD.
Manuele
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Esiste un settore fotografico per cui l'utilizzo del ccd è preferibile al
CMOS versus CCD & what's it all mean?
Back when the D30 was first introduced, Canon's use of a CMOS image
sensor was seen as pretty revolutionary - and it still is. To my mind,
the D30's widely noted superb tonality can be traced directly to the
CMOS sensor technology Canon used in building it. Accordingly, I think
it appropriate to include the following section (copied from our D30
review) here, to give a little background on CMOS vs CCD sensor
technology. (Thanks to IR News Editor Mike Tomkins for his work in
researching and largely writing this technology briefing.) 
To understand what CMOS sensor technology can bring to a digital
camera, first of all you need some understanding of how CCD and CMOS
sensors work, and what they do differently. CCD, or Charge-Coupled
Device image sensors, were invented at the end of the 1960s by
scientists at Bell Labs, and were originally conceived not as a method
of capturing photographic images, but as a way of storing computer
data. Obviously this idea didn't catch on; today we instead have RAM
(Random Access Memory) chips in our computers which are, ironically
enough, manufactured using the CMOS process.
Where CCDs did catch on, however was recording images — by 1975 CCDs
were appearing in television cameras and flatbed scanners. The mid 80s
saw CCDs appearing in the first "filmless" still cameras… CCDs rapidly
attained great image quality, but they weren't perfect. Perhaps most
significantly, CCDs required a manufacturing process which was
different to that used for manufacturing other computer chips such as
processors and RAM. This means that specialized CCD fabs have to be
constructed, and they cannot be used for making other components,
making CCDs inherently more expensive.
Interline Transfer CCDs consist of many MOS (Metal Oxide
Semiconductor) capacitors arranged in a pattern, usually in a square
grid, which can capture and convert light photons to electrical
charge, storing this charge before transferring it for processing by
supporting chips. To record color information, colored filters are
placed over each individual light receptor making it sensitive to only
one light color (generally, Red, Green and Blue filters are used, but
this is not always the case). This gives a value for one color at each
pixel, and the surrounding pixels can provide eight more values, four
each of the two remaining colors from which they may be interpolated
for our original pixel.
After the exposure is complete, the charge is transferred row by row
into a read-out register, and from there to an output amplifier,
analog/digital converters and on for processing. This row-by-row
processing of the CCD's light "data" is where the sensor gets the term
"Charge-Coupled" in its name. One row of information is transferred to
the read-out register, and the rows behind it are each shifted one row
closer to the register. After being "read out", the charge is released
and the register is empty again for the next charge. Repeat the
process a number of times, and eventually you read out the entire
contents of the CCD sensor. (Think of a bucket brigade, moving water
from point A to point B by pouring it from one bucket into the
next...)
A number of disadvantages to this approach to sensor design now become
apparent, in addition to the already mentioned cost. For one thing,
the entire contents of the CCD must be read out, even if you're only
interested in a small part thereof (for example, when using the
digital zooms that are all the vogue in digital cameras, you have no
interest in a large part of the sensor's data, so why take the time to
read it out?) There are also a number of supporting chips required for
the CCD sensor, each of which adds to the complexity and size of the
camera design, increasing cost and power consumption. CCDs also suffer
from blooming (where charge "leaks" from one light receptor into
surrounding ones), "fading" (a loss of charge as it is passed along
the chain before being read out), and smearing (where the image
quality can be adversely affected by light arriving during the
read-out process, leaving streaks behind bright scene areas).
There's also the issue of speed. The step by step process used in a
CCD is not exactly conducive to very high speed, and for just this
reason a second type of CCD exists. The Frame Interline Transfer CCD
features a read-out register as large as the light receptor area is,
allowing the entire contents of the CCD to be read out in one pass.
This, though, adds significantly to the area of silicon required, and
hence to the cost of the CCD.
This is where CMOS image sensors step in. CMOS, or Complementary Metal
Oxide Semiconductor, is actually a generic term for the process used
to create these image sensors, along with numerous other semiconductor
items such as computer RAM, processors such as those from Intel and
other manufacturers, and much more. CMOS image sensors can be made in
the same fabs as these other items, with the same equipment. This
technology is, of necessity, very advanced with the amount of
competition in processor and other markets contributing to new
techniques in CMOS fabrication. Add to this that there is a very
significant economy of scale, when your fab can make not only CMOS
image sensors, but other devices as well, and you find that CMOS image
sensors are much cheaper to make than CCDs.
This cost advantage is even more significant when you consider the way
a CMOS sensor works. The Active Pixel CMOS image sensors used in
digital imaging are very similar to a CCD sensor, but with one major
difference — supporting circuitry is actually located alongside each
light receptor, allowing noise at each pixel to be canceled out at the
site. Further to this, other processes can be integrated right into
the CMOS image sensor chip, eliminating the need for extra chips —
things such as analog/digital conversion, white balancing, and more
can be built into the CMOS sensor. This reduces cost of supporting
circuitry required, as well as camera complexity, and also power
consumption, as does the fact that CMOS sensors require a
significantly lower voltage than CCD sensors. CMOS sensors themselves
also claim lower power consumption than CCD sensors, with one
manufacturer claiming their CMOS sensors draw some 10x less power than
equivalent CCD sensors.
CMOS sensors have other advantages, as well. For one thing, they can
be addressed randomly. If you're only interested in a certain area of
the image, you can access it directly and don't need to deal with the
unwanted data. Blooming and smearing are also less of a problem with
CMOS sensors. CMOS sensors are capable of much higher speeds than
their CCD rivals, with one CMOS chip we've heard of capable of running
at over 500 frames per second at megapixel resolution.
With these advantages, you'd think CMOS would be a shoe-in to replace
CCD in digital cameras, but thus far it has really only impacted the
lower end of the market, with CMOS rapidly becoming dominant in the
entry level digital cameras and tethered cameras. Why hasn't CMOS
taken over at the high end? Well, up until now, image quality has not
been on a par with CCD… CMOS sensors, with their many amplifiers at
each pixel, suffer from so-called "fixed pattern noise". The
amplifiers aren't all equal, and this creates a noise pattern across
the image. In the D60's CMOS sensor, Canon has tackled this by first
taking the image off the CMOS sensor in 10 milliseconds, and then
reading just the fixed-pattern noise from the sensor in the following
10 milliseconds. Subtract the second image from the first, and you
neatly remove the noise.
There's also the fact that CMOS sensors are generally less sensitive
than their CCD counterparts. High end "Full Frame" CCD image sensors
have a "fill factor" of 100%, because the whole CCD sensor area is
being used for light capture — but in a CMOS sensor the fill factor is
lower, because the extra circuitry alongside each pixel takes up
space. This space can't be used to capture light, and so you lose some
of it… Two techniques exist to combat this — firstly reducing the size
of this support circuitry, and secondly the microlens. Reducing the
size of the support circuitry is the less ideal of the two methods —
the smaller you make it, harder the sensor is to manufacture, and the
more expensive it becomes. The microlens is considered to be the
better answer, then. Essentially, the support circuitry is covered by
an opaque metal layer, and a microscopic lens is placed over the
entire area of the light receptor and support circuitry, redirecting
the light that would otherwise fall on the support circuitry and
focusing it on the light receptor.
Canon's EOS D60 is the first high-end digital camera we've seen using
CMOS technology, and it is likely that the projected price advantage
the camera has in comparison with its nearest rivals (the Fuji FinePix
S1 Pro and Nikon D1) is in large part due to the choice of the CMOS
image sensor. The image sensor in the EOS D60 is only ever so slightly
smaller than those used in these two cameras, and significantly bigger
than the sensors used in consumer cameras, as can be seen in the
comparison photo above, which shows the CCD sensor from Canon's
PowerShot S20 digital camera alongside the CMOS sensor from the EOS
D60. The illustration below shows the difference in sizes (to scale)
of a consumer CCD, the EOS D30/60 sensor (they're both the same size),
the D1/D1x/Fuji S1 Pro sensors (also all the same size), an APS film
frame, and a standard 35mm frame.
Canon thus far has been fairly closed-mouthed about their CMOS sensor
technology, but have talked about a few details of it. As with other
Active-Pixel CMOS sensors, theirs does in fact have a signal amplifier
located at each pixel site. More intriguing though, is that they also
claim to have an A/D (analog to digital) converter at each individual
pixel site as well. If this last is true, then it must be a very
different sort of A/D than is normally used with CCDs, as those
circuits are quite complex and space-consuming. We suspect we'll hear
more details as Canon's patent position is solidified, but it sounds
as though there's been some genuine innovation in Canon's back labs.
It's unusual these days to see a company moving toward vertical
integration, developing component technology in-house rather than
farming it out to specialist companies. As the digicam market
continues to evolve, it will be interesting to see whether Canon's
sensor technology will constitute a competitive advantage for them
relative to other manufacturers. (A note, added February, 2002: Canon
has continued to be fairly close-mouthed about their CMOS technology.
No new details have come to us in the year or so since the D30 was
first 

In 
r4fr1vc2mjpfjrije...@4ax.com
, Orsom,
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Acc, Lo stavo per dire io, mi hai preceduto di un soffio...
Ale©s

 Il CMOS e' in poche parole il CCD dei poveri
Mah, e' un'affermazione vera solo per le realizzazioni attuali, le piu' 
diffuse, che hanno la tendenza a produrre oggetti di basso costo, e di 
performance orientate al mobile computing piuttosto che al digital 
imaging in senso stretto. Da questo punto di vista il sensore CMOS 
presenta l'innegabile vantaggio del minor dispendio energetico, elemento 
fondamentale nel sempre piu' affamato universo della telefonia 
cellulare, dove non e' certo la qualita' dell'immagine che fa la 
differenza tra un apparecchio ed un altro.
Se invece vogliamo parlare seriamente dell'argomento "CCD e CMOS", 
allora le cose cambiano parecchio.
Per non scrivere un mega-pippone sull'argomento, vi rimando unicamente a 
questo autorevole link:
http://www.kodak.com/US/en/corp/researchDevelopment/technologyFeatures/c
mos.shtml
Qui viene presentata rapidamente la tecnologia sottostante ai due tipi 
di sensori, con le loro diverse nature.
Non bisogna dimenticare che stiamo parlando di due tecnologie separate 
da quasi *venticinque* anni di ricerca e sviluppo: il CCD ha alle spalle 
una storia molto lunga, e soltanto *oggi* la qualita' dei sensori 
diffusibili presso il grande pubblico commerciale inizia ad essere degna 
di interesse.
-- 
 \\
  \\__ Falco Stellare - falco.s...@TAPPOlibero.it
       <<Togli il TAPPO per avere l'indirizzo giusto>>

 di fondo e prestazioni non esiste CMOS che si avvicini ad un CCD
Anch'io sono astrofilo, e ovviamente confermo quello che dici. Pero' non 
bisogna dimenticare due cose fondamentali, che ho gia' detto un paio di 
messaggi fa:
1) i due tipi di sensori hanno quasi un quarto di secolo tra loro, il 
CCD e' immensamente piu' sviluppato, testato, migliorato, prodotto e 
utilizzato;
2) il CMOS, per le sue caratteristiche produttive, si presta benissimo 
alla produzione di massa a basso costo e a bassa qualita', e questo, 
unitamente alle sue ridotte richieste energetiche, ne fa lo strumento 
ideale per il mobile computing (telefonia cellulare, palmari, webcam, e 
cosi' via) dove la qualita' e' l'ultimissimo dei requisiti.
Cio' non toglie che sensori CMOS, realizzati allo stato dell'arte 
attuale, possano rivaleggiare con i migliori sensori CCD esistenti; 
ovviamente al costo che ci si aspetta per qualcosa che e' ancora 
territorio di frontiera.


 Acc, Lo stavo per dire io, mi hai preceduto di un soffio...
Chiedo scusa, ma qualcuno ha mai sentito parlare di "quoting"?
Lo so che e' un argomento un po' antico, ma magari qualche appassionato 
di archeologia informatica...
No, eh?
Vabbe'...
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