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cyanotype (the “blueprint”), these were unrelated to the
colors of the subjects. He also experimented repeatedly
with silver chloride (see below). As shown below, until
well after 1860 all such attempts by all experimenters
failed to create a permanent color photographic process.
The fi rst hints of a direction for research, however, pre-
date photography by 60 years.
In 1777 Carl Scheele published an account that
showed that silver salts would darken most rapidly when
exposed to the violet and blue parts of the spectrum, and
that the blackened areas were due to the reduction of the
silver salt to metallic silver. Jean Senebier shortly after,
in 1782, published work that showed that it took red light
80 times longer to darken silver salts than violet light.
He also noted a hint of color in the results for different
parts of the spectrum, which foreshadowed Seebeck.
In 1800 Sir William Herschel (John’s father), while
studying the energy distribution in the solar spectrum,
discovered signifi cant heat energy beyond the red end
of the spectrum, later christened the infrared. Spurred
by this result, in 1801 Johann Ritter examined the violet
end by exposing silver chloride (“hornsilber”) to it and
discovered energy beyond the violet, now called the
ultraviolet. He too observed some hints of color at the
blue end of his recording. (Wollaston independently
discovered the ultraviolet shortly thereafter.) Both these
results stimulated awareness of the energetic and chemi-
cal effects differences of different parts of the luminous
spectrum and suggested a way of recording color.
Slightly later Johann Seebeck became interested in
the problem and corresponded with J. W. Goethe who
was then writing his well known book on the theory
of color (Zur Farbenlehre), in which the results of
Seebeck’s experiments were published in 1810 and
thereafter. Seebeck discovered that the solar spectrum,
projected from a prism onto silver chloride sensitized
paper (this was essentially Ritter’s technique), gave
rise to a rough copy of the color at most locations in
the spectrum. Seebeck reported that in the violet he
got red-brown; in the blue, blue, which spread into the
green; he got black or yellowish in the yellow; and in the
red a rose red or hortensia red. But these were of very
unequal quality and could not be fi xed. In a spectrum
attributed to Seebeck in a private collection purple and
violet currently remain visible, though weakly.
In 1839 Sir John Herschel was well aware of
Seebeck’s work with silver chloride and in addition to
trying to use light to bleach out plant dyes he attempted
to make direct positive images by exposing silver
chloride on paper. By adjusting the concentration of
his solutions, the dampness of the paper and exposure
times, he achieved the following results on exposure to
the colors of the solar spectrum in 1840: in the “deep
red and mean red,” no color; orange and orange-yellow,
brick red; yellow, red passing into green; yellow-green
and green, dull bottle green; blue-green, very somber
blue; blue and violet, black, except metallic yellow with
long exposure (which would blacken the rest of the
spectrum); beyond violet, violet–black. These colors
did not appear simultaneously and could not be fi xed.
A bath in sodium thiosulfi te, Herschel’s fi xer, destroyed
the colors.
The prehistory of color photography is much older
than that of black and white, if one counts observations
of dye colors fading in sunlight that undoubtedly go back
to ancient times. This process, by itself, is capable in
principle of yielding a color photographic image. Such
processes were tried by Sir John Herschel (his vegetable
dye experiments) and again in the late 19th century,
then called bleaching-out processes. Start with a range
of light sensitive dyes, in cyan , yellow and magenta.
Generally each dye will fade most quickly when exposed
to light which is its color complement, as this is the color
it absorbs most. In this case the complementary colors
to those above are the primary colors, red, green and
blue. Two problems bedeviled this scheme: the most
“fugitive” dyes that were tried were too insensitive to
result in fading at reasonable camera exposure times.
Secondly, some were too fugitive: no means was found
to prevent their continued fading; the image could not be
fi xed. Image impermanence is still a problem for color
photography (including modern digital printed images),
though progress has been made. A form of bleaching out
is used in some modern color print processes.
Color theory also had a considerable pre-history
by the early 1800s. Newton had (mid-1600s) broken
white light into its spectrum of colors and had shown
that recombining just three colors, red, yellow and
blue, would reconstruct white. Jakob le Blon used those
three colors to do the fi rst practical 3-color printing in
1667, having also concluded that they were suffi cient
to reproduce all the colors of the spectrum. Mixing red,
green and violet light also gave white, and suggested
(around 1800) to Thomas Young that the human eye is
sensitive to just these three bands of color. This theory
was elaborated by Helmholtz, Maxwell and others in
the middle 1800s.
At the beginnings of photography in the 1820s the
gentleman farmer-scientist Joseph Nicéphore Niépce
(later linked to Daguerre) systematically tried a range
of photo processes that included using various resin
and other coatings on metal plates. It is well known that
this eventually resulted in the fi rst photographs, using a
modifi ed camera obscura, in 1827 and 1829. Less well
known is that some of the other processes he tried did
perhaps yield color images. Their potential has recently
been demonstrated by J-L Marignier at Orsay and Marc
Kereun of Paris, in trials using Niepce’s original recipes.
Exposure times were very long.
However, neither Daguerre’s process nor Talbot’s