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

particles of starch-grains, dyed red-orange, green, and blue-violet, and spread
in such proportions on the plate as to produce a grayish white. This theory
of the polychrome screen, like almost every development in three-color
photography, originated with Louis Ducos du Hauron, who described a
method of making what he actually referred to as a grain-screen, in his
mémoire on the subject of color photography, published in 1868; and he
referred to the theory in a communication to M. Lelut in 1862. In 1869,
under the title, " Les Couleurs en Photo Solution du Problème," he minutely
described this among other methods of producing an image in color by
photography, but the primitive state of photography itself made the execu-
tion of most of his ideas impossible at that time; and yet it is recorded that
on the seventh of May, 1869, formally laid his theories before the
“Société Française de Photographie.” By a curious coincidence Charles
Cross presented his version of the three-color problem the same day at the
“ Société ; ” both men working along the same lines unknown to each other.
Ducos du Hauron actually accompanied his description with two three-color
pigment prints of a disque divided into color-sections, which it was stated
gave quite a close rendering of the original. This seems almost impossible
in view of the undeveloped stage of photography at the time as regards a
color sensitive emulsion, but the facts stand recorded, and so do the pathetic
chapters in the story of the life of this great, unappreciated genius. He is
still laboring and experimenting in poverty and seclusion, while we are
enjoying the results of his genius, and capital is getting itself together to
reap a golden harvest out of his “ impractical discoveries.”
The Lumière Autochrome Plate is prepared as follows: By a me-
chanical selecting process starch-grains of about the same size are chosen
and then dyed red-orange, green, and blue-violet respectively. When dry
they are thoroughly mixed in the bulk to produce a neutral grayish tone—as
a matter of fact the green particles predominate. Examined with a micro-
scope the colors seem a rich vermilion, a yellowish green, and a reddish
ultramarine blue. The glass is first coated with an adhesive varnish and the
mixed colored starch dusted on, and as the starch will only adhere to the
sticky surface there is practicaliy no overlapping. Then the starch-grains
are crushed flat by a special method devised by the makers, which permits
of enormous pressure on the glass without breaking it. This flattening
makes the grains more evenly transparent and helps close up the spaces
between them. The remaining interstices are then dusted in with carbon
black. There are from four to five million of these particles of color
to the square inch, and they are naturally so small as to be invisible to the
naked eye, or even when examined with a lens. The fine granular appear-
ance of the plate is due not to the individual grains, but to little groups of
grains in which a certain color predominates, making it look like a grain of
bright color—for this reason the layman often thinks he detects grains of
yellow and of blue in the film. If it were possible to mix the particles and
coat them absolutely evenly, the grain would not be visible at all; but even
distributed as they are, Baron von Hübl has calculated that two thousand
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