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scheme. It was described by du Hauron in his 1868
patent: “Finally there is another method by which the
triple operation may be effected on one surface. The
separation of three elementary colors may be effected
no longer by three colored glasses, but by means of
one translucid sheet covered mechanically by a grain
of three colors.” McDonough’s patent refers to this
grain idea, later used successfully by the Lumieres,
but he gave up on it and adopted the ruled overlapping
line-screen approach, as used by Joly and a number of
others. These screens consisted of fi ne lines alternating
red, green and blue. The layout varied, in some cases
they were interleaved parallel colored stripes, in others
the screens crossed each other at right angles, yield-
ing color patches which were square. The image was
recorded through the screen on black and white fi lm,
developed and either redeveloped to a positive or a
positive copy was made. In most of these processes the
fi nal positive was mated with a color screen identical
in layout to the taking screen, and in other versions the
screen was bound to the emulsion from start to fi nish.
(The former version suffered from color fringing and
Moire patterns if the screen and image were not perfectly
aligned. The Paget process in England, and the Dufay
color and Omnicolor (du Hauron’s last hurrah) processes
in France, came on the market in the early 1900s and
the latter two enjoyed reasonable success. All these
processes were slow compared to black and white, and
required exposures of several seconds in bright sunlight,
even with the fastest fi lms. A particular disadvantage of
the regular line screens was that, though their patterns
at 200 to 400 lines per inch were invisible to the naked
eye on the originals, modest enlargement would reveal
the pattern, which was annoying.
In 1891 a radically different color process, the inter-
ference process, the one not predicted by du Hauron, was
announced by Gabriel Lippmann, professor of physics
at the Sorbonne. He was motivated to invent it in order
to confi rm the wave nature of light, and according to
several of his accounts it took him 12 years to achieve
a fi ne-enough grained emulsion for the purpose. He
realized light could be made to record itself, color by
color, if a way could be found to let each color (wave-
length) interfere with itself, and to capture that stand-
ing wave pattern of nodes and vibrations on fi lm. Each
layer created would be a half wavelength from the next,
throughout the depth of the emulsion. He completed
a full mathematical theory based on Fourier analysis,
employed in the same way as it was used to analyze
complex sounds, before he achieved any experimental
results.
To record blue, which has the shortest wavelength,
required resolution better than 10,000 lines per mm, a
factor of 100 better than most commercial fi lms today,
and as good as the best current holographic fi lms. He
imagined the pattern could be created by refl ecting the
image’s light back on itself using a mirror, but due to
the impurity of ordinary light the pattern would exist in
a layer of space in front of the mirror only about 2 mi-
crons (0.002 mm) thick. To provide the required perfect
contact between mirror and emulsion, he ingeniously
employed a special plateholder with a thin pocket behind
the plate into which he poured mercury. The emulsion
faced the mercury and away from the camera lens and
light entered through the plate’s glass surface. He fi rst
demonstrated the recording of a spectrum, a 12-hour
exposure, on silver halide albumen emulsion. He also
pointed out that any panchromatic black and white
emulsion of suffi cient resolution would work and he
demonstrated this by showing images on collodion,
silver halide gelatine and dichromated gelatine. St. Flo-
rent made Lippmann images using iron salts in gelatine.
Recently Hans Bjelkhagen and Jean-Marc Fournier have
produced Lippmann images in photopolymers.
There was controversy at the beginning over whether
this process gave good color. But after the Lumiere
brothers tried it, along with Eduard Valenta and Dr.
Richard Neuhauss who improved on Lippmann’s
emulsions, there was no doubt of its potential. Eduard
Steichen commented in a Camerawork issue of 1908:
“The rendering of white tones was astonishing, and a
slide made by one of the Lumiere brothers.. a slide of
a girl.. was simply dazzling, and one would have to go
to a good Renoir to fi nd its equal in color luminosity.”
Altogether perhaps 8 to 10 professionals and about
twice as many amateurs tried the process. Around 1900
Penrose in England produced the special plates and
plateholders required, as did Cheron and Mackenstein
in Paris and Jahr and Zeiss in Germany. More than 500
images exist by the Lippmann process, and some of
these, including portraits, still lifes and landscapes, have
truly spectacular color.
Over the next decade Krone and then Rothe showed
that Lippmann pictures could be made without the
mercury mirror, relying solely on the slight refl ection
of light at the gelatine-air interface. The colors were
less saturated. Today a few people are trying to improve
on this approach, including the author, and the above-
mentioned Mr.’s Bjelkhagen and Fournier.
Lippmann’s process provided amazing color, color
permanence (no dyes were needed for the fi nal image,
and the emulsion was sealed from the air under a prism
used to improve viewing contrast), and superb resolution
that allowed immense grainless projections. Neverthe-
less, the process was never commercialized. Perhaps one
reason was that Lippmann did not patent it, which low-
ered the incentive for a manufacturer. Nonetheless, the
Lumieres tried hard to industrialize it from 1891 to about- They were not able to achieve reliable results.
This was likely the decisive factor, though others were