319
by chance its contribution to the colors gave a “red”
which was about right.
In 1862 Louis Ducos du Hauron (1837–1920) sent
one of his friends a letter, to be read at the French Acad-
emy of Sciences. It described several ideas for color
photography based on color separation. The paper was
never presented. du Hauron continued his work, mak-
ing some early images which combined photographs
and carbon-based pigment prints, which still exist and
are rather beautiful. By 1867 he had refi ned and ex-
panded his ideas. He received a French patent on them
in 1868. In that patent and one received in England in
1876 du Hauron laid out all color processes, save one,
attempted since.
In 1869 he submitted a paper on his ideas to the
Société française de photographie. Completely inde-
pendently and unbeknownst to du Hauron, Charles Cros
(1842–1888), a French poet and dilettante who among
other things, invented the disk phonograph before Edi-
son, submitted a detailed proposal for one of these ideas
to the Society within days of du Hauron. The papers
were opened and read at the same session. It turned out
Cros had also sent a sealed letter describing his ideas to
the French Academy of Sciences in 1867. A potential
priority dispute was fairly quickly squelched by the ac-
tions of both men, who quickly became friends.
Their common idea was that of sandwiching three
layers of emulsion, each absorbing one of the 3 pri-
mary colors, each containing a dye that passed its
color complement. This process is the basis of every
successful modern color process, and is usually termed
a “subtractive” process.
The other main classes of ideas outlined in du
Hauron’s patents, termed “additive,” included the color
separation processes, as fi rst demonstrated by Maxwell
(see above), and the color screen processes. The latter
included various schemes to fi lter the picture plane into
small regions of the three fundamental colors, for taking
and viewing.
All these ideas were initially impossible to imple-
ment, because the emulsions of the day were only
sensitive to blue light (termed isochromatic), whereas
every proposed color process required making images
which included the whole of the spectrum. In the early
1870s the German chemist H. W. Vogel (1834–1898)
discovered by chance that adding dyes to the silver
halide-based collodion and gelatine emulsions could
extend their sensitivity out into the green, and ortho-
chromatic emulsions resulted. His discovery was not
immediately accepted as, for a short time, others failed
to duplicate his results. When he pointed out that they
had used such high dye concentrations that all light was
absorbed before reaching the silver halides, and lower
concentrations would do the trick, he was ridiculed.
One critic reasoned (falsely) that following Vogel’s
suggestion, it was logical to expect that the dye would
work best at zero concentration, not realizing that Vogel
was correct and that there was an intermediate optimum
concentration.
In the 1880s and 90s Vogel and others systematically
extended this idea into the yellow and red, as well as
showed that dyes could enhance the emulsions’ original
sensitivity in the blue. This advance created increasingly
sensitive black and white emulsions. By the 1880s this
improvement, coupled with advances in the speed of
photographic lenses, permitted photographers routinely
to take exposures at speeds greater than 1/30th of a sec-
ond, allowing the making of what were called “instant”
images that could freeze ordinary motion. This created
a rage for motion capture, as well as the possibility of
making sequences of moving images. It also made pos-
sible the creation of panchromatic emulsions for color
(and black and white) fi lms, and the possibility of stable
dyes to use in the resulting fi nal colored images.
The separation processes were pursued by du Hauron
and others. In the 1860s and 1870s he built cameras,
camera backs and viewers (Chromographoscopes),
designed to take and display three color-separated
plates in sequence or simultaneously, and tried to com-
mercialize them. He was not successful, though as
mentioned above, some of his carbon-based prints,
which required no viewer, survive, as do some of his
Chromographoscopes.
The 1870s and 1880s saw attempts to make practical
use of du Hauron’s ideas, but with little success. In the
early 1890s the situation changed. In the U.S., Frederick
Ives (1856–1937), already known for his inventions in
color printing processes, turned to color photography
and made a range of cameras, viewers and projectors to
employ the 3-color separation process, using the new
panchromatic plates and fi lms. He called his equipment
Kromscops, riding the commercial coattails of the let-
ter “K” which resulted from George Eastman’s success
with his Kodak cameras. In some versions the images
were made in succession, for which the equipment was
a sliding back, and optically straightforward. In others,
using a more complicated arrangement of internally
mounted color-separating (“dichroic”) partially refl ect-
ing mirrors, the images were made simultaneously. The
latter arrangement was bulky, but avoided the problem
of color fringing due to subject movement between
exposures, which images by the other method suffered
from. He lectured frequently and widely, disputed the
importance of du Hauron’s and Cros’ ideas, and tried to
sell his equipment on the Continent as well as the U.S.
He was modestly successful.
Also in the 1890s the fi rst screen processes hit the
market. McDonough in the U.S. in 1892 and Joly in
Ireland in 1894 each patented and began to sell fi lm and
screen fi lters for making color photos by this general