Let us suppose, for the purposes of explanation, that as far as _seeing_
goes, any object is made up of countless infinitesimal points of light,
and that the business of the eye is to gather them in and spread them
out at the back of the eye in exactly the same relation they bore to
each other on the object. The points of light, so duplicated, would thus
form the image of the object.
The camera works very much the same way. The lens at the front of the
camera is the eye, and the plate or film at the back of the camera
corresponds to the back of the eye. The lens collects all the points of
light of the object we wish to photograph, and directs them to the plate
or film in such fashion that they occupy exactly the same relative
position that they did before. An image of the object is formed.
Now if we could look inside the camera and the image were visible, we
would see that it was upside down. The reason for this is very simple,
as the accompanying diagram shows. The ray of light from “A” at the
bottom of the object passes through the lens at an angle, and continues
in a straight line until interrupted by the film or plate. It started at
the bottom of the object and ended at the top of the image. The position
of all the points of light is just reversed, although their relative
position remains the same.
[Illustration: SHOWING INVERSION OF THE IMAGE]
“Then here,” you say, “is where your analogy between the camera and the
eye falls down.”
Not at all. It is true that we do not see things upside down, but this
is because of mental readjustment during the passage of the impressions
from the eye to the brain.
Now let us suppose that we have our camera loaded with film, and that
mother has succeeded in keeping the baby quiet long enough for us to
uncover the lens for an instant and let the points of light through to
the film. The next question is, how are we going to make the resulting
image permanent. We know that it is there, but in its present state it
is not going to do us a great deal of good. In fact, if we should peek
in the back of the camera, and to do so would ruin the exposure, we
could not even see it.
But let us go back a bit. We ought to know a little something about the
composition of this film on which the image has been projected.
In brief, film is a cellulose base coated with silver bromide and
gelatine. If we were using a plate the only difference would be that
instead of cellulose as a base we would have a sheet of glass. The
gelatine is there to afford lodgment to this sensitized silver. The
silver, being sensitive to the action of light, is there to record the
image. As soon as one of these silver particles has been touched by
light, it becomes imbued with the power of holding whatever the lens has
transmitted to it. The image was formed, we remember, by points of light
grouped in the same relative positions as the points of light of the
object we were photographing. Consequently it is only those silver
particles within the image-forming area that are affected, because that
is where the light struck.
The lens, then, gathered in the points of light and dispersed them on
the film so as to form an image. The silver particles held this image,
but not visibly--it is a latent image, and it is the purpose of
development to bring it out.
It is the particular business of a chemical called “pyro” to release
this latent image. When attacked by pyro, those silver bromide particles
which have been affected by light--and only those--change to black
metallic silver. After all the silver bromide particles, the ones that
held the image, have been transformed into metallic silver, another
chemical called “hypo” effectively disposes of all the silver bromide
that was not affected by light. Now only the image-forming silver
bromide particles remain, and these have been transformed to metallic
silver. The result is a permanent image--a negative.
But it _is_ a negative, so called because everything in it is
reversed--not only from left to right, but in the details of the image.
Mother’s dark blue gown looks light, for example, and baby’s white
dress, dark.
To get our picture as it should be, we must place the negative in
contact with a sheet of paper coated with a gelatine containing silver.
This emulsion, as the coating is called, is, as we might readily infer
from the presence of the silver, sensitive to the action of light in
much the same manner as was the original film. We place the negative and
paper in contact, then, in what is called a printing frame, so that
light may shine through the negative and impress the image on the
sensitive paper. It is obvious that the light parts of the negative will
let through the most light, and that consequently the silver emulsion on
the paper underneath will be most blackened, while the dark parts will
hold back the light and the emulsion on the paper underneath will be
less affected. In other words, the very faults that we noted in the
negative, from a picture point of view, automatically right themselves.
Mother’s dress looks dark and baby’s dress white--just as the lens saw
it.
We then have the picture in its finished form.
The story of the making of the camera is as interesting as that of the
making of the pictures by the camera.
Back in 1732, J. H. Schulze discovered that chloride of silver was
darkened by light and all unwittingly became the father of photography.
In 1737, Hellot, of Paris, stumbled on the fact that characters written
with a pen dipped in a solution of silver nitrate would be invisible,
until exposure to light, when they would blacken and become perfectly
legible. However, it was not until early in the nineteenth century that
these two discoveries were put to any practical use, as far as
photography was concerned.
People of an artistic turn of mind had been in the habit of making what
were called “silhouettes.” The sitter was so posed that the light from a
lamp threw the profile of his face in sharp shadow against a white
screen. It was then easy enough to obtain a fairly accurate silhouette,
by either outlining the profile or cutting it out from the screen.
It occurred to a man by the name of Wedgwood that this profile might be
printed on the screen by using paper treated with silver nitrate, and he
not only succeeded in accomplishing this, but also in perfecting what
was then called the “camera obscura,” the forerunner of the kodak of
today. The camera obscura consisted of a box with a lens at one end and
a ground glass at the other, just like a modern camera. It was used by
artists who found that by observing the picture on the ground glass they
could draw it more easily. Wedgwood tried to make pictures by
substituting his prepared paper for the ground glass, but the paper was
too insensitive to obtain any result. Sir Humphrey Davy, continuing
Wedgwood’s experiments, and using chloride of silver instead of nitrate,
succeeded in making photographs through a microscope, by using
sunlight. These were the first pictures made by means of a lens on a
photographic material. But none of these pictures were permanent, and it
was not until 1839 that Sir John Herschel found that “hypo,” which he
had himself discovered in 1819, would enable him to “fix” the picture
and make it permanent.
At about this time, Daguerre announced discoveries that gave photography
at least a momentary impetus, but the Daguerre process did not long
survive, as it was slow, costly and troublesome. The daguerreotype was
made on a thin sheet of copper, silver plated on one side, polished to a
high degree of brilliancy, and made sensitive by exposing it to the
fumes of iodine. The first daguerreotype made in America, that of Miss
Catherine Draper, was exposed for six minutes in strong sunlight, and
the face of the sitter thickly powdered, to facilitate the exposure. An
exposure today with a modern camera, under similar conditions, could be
made in 1/1000 of a second.
[Illustration: ARTOTYPE COPY OF THE EARLIEST SUNLIGHT PICTURE OF A HUMAN
FACE
Miss Dorothy Catherine Draper, taken by her brother, Prof. John W.
Draper, M.D., LL.D., in 1840.]
It was impossible, of course, to find many sitters as patient as Miss
Draper--try keeping perfectly quiet for even a minute if you would know
why Miss Draper should be ranked as a photographic martyr--and many
experiments were made in an attempt to materially shorten the time of
exposure. The only real solution, of course, was to find some method
where the light had to do only a little of the work, leaving the
production of the image itself to chemical action.
[Illustration: OLD-FASHIONED PHOTOGRAPHIC EQUIPMENT]
The first great step in this direction was taken by Fox Talbot in 1841.
He found, that if he prepared a sheet of paper with silver iodide and
exposed it in the camera, he got only a very faint image, but if, after
exposure, he washed over the paper with a solution of silver nitrate and
gallic acid, the faint image was built up into a strong picture. And not
only was Fox Talbot the first to develop a faint or invisible image; he
was also the first to make a negative and use it for printing.
[Illustration: THE FIRST KODAK (1888), SHOWING ROLL HOLDER AND ROLL FILM
FOR 100 EXPOSURES]
[Illustration: THE FIRST DAYLIGHT LOADING METHOD]
[Illustration: THE FIRST “FOLDING KODAK” FITTED FOR PLATES OR ROLL FILM]
[Illustration: “DOPE” BARREL]
In spite of all these advances, photography was almost exclusively a
studio proposition, when, in 1880, experiments were begun which were to
result in photography that could be universally enjoyed--photography as
we know it today. Of course there were amateurs even in those early
photographic days, but they were few and far between. There was
something about the bulk and weight of the old-time photographic outfit
that failed to beget general enthusiasm.
[Illustration: RAW STOCK ROLLS, KODAK PARK]
[Illustration: ASSEMBLING ROOM, CAMERA WORKS]
To lighten the camera burden, and to simplify the various photographic
processes, were the problems that confronted the American inventor. The
first step toward film photography--and it was film photography that
relegated camera bulk to the scrap heap--was a roll film made of coated
paper to which a sensitive emulsion was applied, but the real goal was
reached when cellulose was substituted as a film base. This made
practicable the present flexible, transparent film with its attendant
convenience and dependability.
The kodak was the natural outcome of the roll film system. The first one
appeared in 1888, and its development, which proceeded simultaneously
with the film discoveries, soon reached the point where the loading and
unloading could be done in daylight. Daylight developing soon followed,
and the dark room, as far as the kodaker was concerned, took its proper
place as a relic of the dark ages.
With 1914 came autographic photography, so that now with a kodak in one
pocket and a handful of film in the other, the amateur is equipped for a
picture-making tour of the world--not simply a pictorial record, but a
written record as well, for autographic photography permits the dating
and titling of each negative directly after exposure.
Photography, not so many years ago an exclusive pleasure for the few, is
now easy fun for millions.
[Illustration: FILTER ROOM, KODAK PARK