Evening star. [volume] (Washington, D.C.) 1854-1972, 1911-07-06

The aim OF the men who are expert
menting in color photography is to
produce a pho
Tries to Duplicate tographic plate
Work of Painter. a,io..s tho
work Of the
painteh without involving the long and
tedious processes he must employ. The
main value Of the present sort of color
photography is to furnish key to cor
rect coloring for the printer. Former
ly, when seed establishment, for In
stance, wanted to portray Its fruits
and vegetables in their natural colors,
1t was necessary to engage an artist
to paint the picture of each vegetable
and fruit to be illustrated. his work
to be followed by that Of the engraver
or photographer. Today he may make
a picture upon a color plate. and rid
himself OF the major portion of the
expense Of preparing his seed cata-
logue.
There are many processes Of color
photogra ply in use today, each afford
ing a considerable range for the re-
production Of colors. and each pos
sessing certain advantages over other
processes, but none Of them as yet has
been able to offer the most essential
item necessary to successful color pho
Biography Photographic paper
which is able to receive satisfactorily
the color impression. There are many
|. investigators who declare that such a
paper cannot be made.
Color photography is based upon the
accepted theories of light rays. II has
long been known that a ray of light
passing through a prism. the simplest
form of a spectroscope, is broken up
into the colors of the rainbow. Not
only is the scientist able to analyze a
light ray as the chemist analyses a
chemical compound but he is able to
build 1T up again. This can readily
be illustrated with three pieces of col
ored glass IL one takes these three
pieces, one red, one green and one
blue-violet. and puts them all to-
gether the light passing through them
will be white. Taking any two Of the
three pieces he may make still differ
ent colored lights.
Another property of light which has its
bearings upon color photography is the
fact that il consists
Measure Length OF waves of varying
of Light Rays. l nays been S ss'e fo
devise measuring machines which can
measure distance much shorter than the
millionth part of an inch. With these
instruments they have been able to
measure the length of the light rays
which make the different colors.
In one of the processes Of color pho
Biography a glass plate is covered with
an emulsion perfectly transparent, and
exposed in the camera, with the glass
side to the lens. and with the film side
backed up with mercury. In ais way
the brilliant mirror OF the mercury comes
in close contact with the finn and re-
fleets back upon itself the light which
comes from the lens. The film must be
transparent and thick enough for one or
TWO of the longest light waves to be
fully formed within il. Where the light
waves collide there will be no image:
where they do not come together an
image will appear. The result of this is
that when a plate has been exposed, de-
veloped and dried there is :. film upon
the glass i'm which the image consists
of series of layers of extremely thin
deposited silver, separated by equally thin
LAYERS of clear gelatin. When these lay
ers are seen in light falling upon them
at a certain angle they show colors just
as a soap bubble does. In this way parts
of the original which are red appear in
the same color in the picture. and the
same is true of other colors, though none
of them is exactly true TO nature.
Another process employs three different
negatives Suitable screens are inter-