This is a picture of Dr. Rudolf Fischer,
who was born on January 27, 1881 in Berlin. When he turned thirty over
100 years ago, he was working as a chemist at the NPG in
Berlin-Steglitz. Together with his colleague Dr. Hans Sigrist he had the
basic idea for the modern color film and they got granted two patents.
Interestingly, patent DRP 253335
has been registered to Rudolf Fischer himself and covers the basic
chemical idea for the formation of dyes during the film development
(granted on February 7, 1912). In contrast, DRP 257160,
which according to the number was filed later, has been registered to
the NPG and was already issued on the June 14, 1911. It describes
several ways of technical implementation for color photography,
including the multilayer color film as we know it today.
The Neue Photographische Gesellschaft
(New Photographic Corporation, NPG) was the largest photo company in
the world these days. However, they could neither sustain their
importance through the First World War, nor make any use of the
pioneering patents for the multilayer color film. Before the war, they
used the new findings to produce the so-called Chromal Paper, though.
This specialty was offered in ten different colors, however, pictures on
it were not actual color photographs, but only colored black and white
photos.
What was the revolutionary idea,
though? Fischer was looking for ways to generate a colored instead of
the black image, which is known to stem from colloidally dispersed
silver. He knew that some developers,
if you did the development not quite correct (you must omit the
sulfite) lead to colored images. He realized that the coloring
substances are the oxidation products of the developer (in return the
silver halide is reduced to form silver). Fischer stated (in DRP
253335): "The thereby achieved colorations may not be very prominent
[...]. It has now been found that one can get to extremely strong
colored images [...] by adding [colorless] substances to the solution
which couple with the oxidation products formed during development and
lead to insoluble colored bodies." Today, in photochemistry we call
these substances color couplers and they are actually part of the
developer chemicals (Kodachrome process) or far more prevalent
(Agfacolor, Ektachrome, etc.) included in the film emulsion.
Interestingly, it is possible to use only one single developing agent
(for example N, N-diethyl-p-phenylenediamine) and three different color
couplers to produce the three primary colors.
In
DRP 257160 Fischer described the structure of the modern color film
quite accurately (page 2, lines 12-36). He even did not forget to
mention the yellow filter layer (lines 52-58). In the last section of
the description, just before the examples he named the remaining
unsolved technical problem: "... to prevent the diffusion of the
coloring substances [between the layers]". His proposed solution using
intermediate layers failed later. This problem, which for about 20 years
prohibited a successful commercial multilayer color film, was
eventually solved. Not only one solution was provided, it was even done
twice independently, in order to be optimized again for the latest
method still used today. More about these things later…
Fortunately,
Rudolf Fischer was allowed to witness this breakthrough. Because of the
by then expired patents he did not made any money with his invention.
Instead, in 1944 for his contribution to color photography he was
awarded the silver Leibniz Medal from the German Academy of Sciences.
Otto Hahn gave the eulogy, present were also Max Planck, Werner
Heisenberg, and other notables.
Further reading (unfortunately all in German): Wolfgang Holtz "Die Neue Deutsche Photographische Gesellschaft" in Arbeitskreis Bild Druck Papier - Tagungsband Nürnberg 2009; Prof. Dr. Rudolf Gschwind, Imaging and Media Lab, Uni Basel, Vorlesungsskript Bildtechnologie I, Teil 5.
Other parts of this little history series...
2) Kodachrome 3) Agfacolor Neu
4) Ektachrome and Kodacolor
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