Evening star., 1955-10-30
CAMERA ANGLES
~ 4. J. WEDDERBURN
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Curator Of Photography.
ne Smithsonian 1nstttution
There are three distinct
operations involved in making
q photograph. First the image
Is recorded on the film: then
this image, which is invisible
to the eye. must be made
visible: and finally the image
must be transferred to paper
or some other recording sub
stance. Today we win discuss
the second step that Of BRING
ing the invisible picture to
Life.
When we press the shutter
release on the camera. . Light
reflected image OF the scene
passes through the lens and
Is recorded on the sensitive
emulsion Of the film. This
image, as most of US know by
now, is not visible to the eye.
tits known as the latent image
and the film must be sslbmitted
to chemical treatment 1 ring
out the hidden picture.
All Aims are alike insofar
as each is extremely sensi-
tive to light. During the ex-
posure, certain areas Of the 1ilr1
are greatly affected while other
parts are to lesser degrees. A
white dress will reflect more
light than q red blouse, 50 II
Is easy to appreciate that the
part Of the film affected by
light reflected from q dark
area of the scene win have
less reaction than that part
which receives the more bril-
liant rays.
What Developing Does
Now let's see what happens
when We place the exposed
film In o chemical bath called
the developer. This is simply
o specially compounded for
nula which viii remove the
emulsion In direct proportion
to the amount Of light It has
received. Otherwise, We. would
have d fllrn Of neutral overall
density or no picture at all. In
portions Of the film upon
which little or no light was
reflected the unused" emui-
sion win slough on into the
developer leaving the film base
clear, or almost 30. depending
upon the amount Of exposure.
II any. Areas Of the film that
were strongly affected or ex-i
posed viii retain much Of the
coating. and other areas more
or less acted upon win release
corresponding amounts Of the
coating into the developer,
Upon completion Of deyelpp-
ment the film win have . pic
t1re which has been formed
by this process Of the release
OF proportional amounts Of the
emulsion. From the above. III
viii be apparent that now.
however. the original white
areas will look black on the
negative and the original black
areas white with the inter-
mediate tones reversed propor-
tionately. This is called the
negative image. To re-reverse
the image and come UP with q
positive image. or one which
Is like the original subject.
light must be passed through
the negative to form a second
image on another light-sensi-
tive substance. This Is usually
the paper we use to make our
prints.
It can be seen that the clear,
or least affected portions Of the
negative win permit a greater
amount Of light to reach the
sensitive paper, producing a
black or dark tone upon devel-
opment Of the second image.
The dark-appearing portions
of the negative will allow less
light to reach the paper, thus
producing white or grey tones
Id the final print. Conse-
quently, the paper print viii
resemble the original scene
tonally.
> Steps for Processing
Processing Of both films and
prints involves three identical
steps. These are development
of the latent image. stoppage
Of the development action.
and fixing or making perma-
rent the image.
In the case of film proc
essing, one of several methods
may be employed. The films
can be processed in trays. or
In deep tanks, or In closed So
called daylight tanks for roll
films. When trays or deep
tanks are used three vessels
should be employed. One will
hold the developing solution.
another the short-stop solu-