Camera Work: A Photographic Quarterly (1908 (Heft 22))

Although we give to the Lumière brothers the credit of giving us the
first practical solution of color photography, in the form of a commercially
available plate, we must not forget Professor Lippman, who gave us what is
undoubtedly the most wonderful process of color photography. The
Lippman process is undeniably real color photography, for the question of
actual coloring matter does not in any form enter into the making of the
image, and we have a plate which is actually colorless and resembling an
ordinary plate. Yet when seen at a certain angle by reflected light, a beau-
tiful, iridescent image becomes apparent, which when shown by reflection in
a projecting lantern, has all the startling realism that the image in a mirror
conveys. Professor Lippman has shown me slides of still-life subjects, by
projection, that wrere as perfect in color as is an ordinary glass-positive in the
rendering of the image in monochrome. The rendering of white tones was
astonishing, and a slide made by one of the Lumière brothers, at a time
when they were trying to make the process commercially possible, a slide of
a girl in a plaid dress on a brilliant sunlit lawn, was simply dazzling, and one
would have to go to a good Renoir to find its equal in color luminosity.
According to Professor Lippman, even a rapid lens requires an exposure of
about two minutes in full sunlight; and then the result can only be properly
seen by projection; so the process remains for the present, at least, imprac-
ticable. The actual laws governing the making of the Lippman Helio-
chromes are infinitely more complicated and difficult to explain to the
layman than the actual making of the picture, but the following graphic
summary by Dr. Koenig is very comprehensive: “ If a plate coated with
a transparent or so-called grainless panchromatic emulsion is exposed
through the glass with the sensitive film in intimate contact with metallic
mercury, the reflected rays of light interfere with the incident rays and pro-
duce in the sensitive film fine laminæ of metallic silver, separated by half a
wave-length of the light that produced them. These layers appear brownish
when looked through, but when examined by reflected light produce per-
fectly the colors of objects ."
Taking three pieces of colored glass of the primary colors, one orange-
red, one green, and one blue-violet, and examining a color chart with them,
we find that the blue glass screen acts as a filter and absorbs its comple-
mentary color—yellow, and such parts of other colors having yellow in
their make up will be represented in varying degrees of dark blue, the pure
yellow looking darkest. Placing this screen before the lens on a camera and
then photographing the color chart, the screen filters the light as above
described and only the radiations of violet-blue and red in the chart reach
and act upon the photographic plate. When the plate is developed and
printed, yellow will be represented by black, the parts representing green,
orange and vermilion will be a dark gray, and pure blue will appear as the
lightest tone. This plate then contains the yellow element of the three-color
picture; and in a like manner the green filter makes red-orange and violet
look dark, and green-blue and yellow light, for it absorbs the reds, and the
only rays that will affect the negative are the radiations of green and a part