The Lippman process is a color photography technology based on direct recording of the spectral composition of radiation. For this, the distribution pattern of standing waves generated in a thick emulsion as a result of light interference is fixed. The first color photograph was obtained by Gabriel Lippmann using this process in 1891 , and a year later the results of successful experiments were demonstrated at the Paris Academy of Sciences [1] .
Content
Physical Principle
Unlike conventional color processes based on Maxwell’s three-color theory, the Lippmann process does not require color separation and reverse color synthesis from three partial images. Recording color information about the objects of shooting takes place directly, due to the interference of light waves inside a gelatin-silver photosensitive material with a thick panchromatic emulsion [2] . The latter is placed on a mirror surface, fully reflecting the incident light on it back into the photosensitive layer. As such a surface, a mercury layer was used, poured between the photographic plate and the wall of a special cartridge [3] [1] . The interference of the incident and reflected light fluxes leads to the formation of standing waves in the emulsion layer. After laboratory treatment , microscopic layers of metallic silver are formed in the emulsion, corresponding to the arrangement of standing waves, which depends on the spectral composition of the exposure radiation [4] . The thickness of the layers is half the wavelength of the exposure radiation, therefore, the resolution of the emulsion must be very high [5] . The size of silver microcrystals of the first Lippmann plates did not exceed 0.04 microns [3] .
When the developed plate is illuminated with white light, interference emission of light of the wavelength that created the corresponding distribution of blackening occurs. In other words, only waves of the same length as the exhibiting light are effectively reflected, while all the others are attenuated or damped. Therefore, the spectral composition of the radiation reflected by the developed photographic plate completely coincides with the spectral composition of the light that fell on it at the time of shooting [2] . In this case, a positive image is formed directly in the photographic material on which the picture was taken. The color reproduction resulting from the Lippman process is physically accurate (or “spectrally accurate”) in contrast to other color reproduction methods based on the metamerism of human vision, and capable of providing only physiological accuracy. In the general theory of his process, for which he was awarded the Nobel Prize in Physics in 1908 , Lippman actually proved that the inverse Fourier transform occurs upon interference [2] .
Strengths and weaknesses
The Lippmann method of color photography provides color accuracy that is sufficient even for spectrometry of the radiation of the subject. However, the special grainless emulsions necessary for recording the wave pattern have a very low photosensitivity , requiring long exposures even in bright sunlight. Consideration of the finished image is also fraught with certain difficulties, since the image is distinguishable only at a certain angle, as in the daguerreotype [1] . In addition, duplication of Lippmann’s photographs in their original form is impossible, making them unsuitable for use in the publishing business. Each photographic plate is unique and image enlargement or reduction is also not available. Later, a slightly modified version of the process was used for color holography according to the method of Yuri Denisyuk [6] . The process found practical application in the field of protection against falsification , due to the impossibility of full copying.
See also
- Integral Photography
- Nuclear Photographic Emulsion
Notes
- ↑ 1 2 3 Soviet photo, 1982 , p. 41.
- ↑ 1 2 3 Grebennikov, 1982 , p. 162.
- ↑ 1 2 Color reproduction, 2009 , p. 6.
- ↑ Volumetric photography technique, 1978 , p. 61.
- ↑ Color reproduction, 2009 , p. 7.
- ↑ Photokinotechnics, 1981 , p. 403.
Literature
- V.I. Vlasenko. Chapter III. Integral photography // Volumetric photography technique / A. B. Doletskaya. - M .: "Art", 1978. - S. 36-66. - 102 p. - 50,000 copies.
- O.F. Grebennikov. Chapter IV Recording and reproducing a color image // Fundamentals of recording and reproducing an image / N.K. Ignatiev, V.V. - M.,: "Art", 1982. - S. 162-201. - 239 p.
- E.A. Iophis . Photokinotechnics / I. Yu. Shebalin. - M.,: “Soviet Encyclopedia”, 1981. - S. 401-404. - 447 p.
- Maxim Tomilin. From the history of color photoprocess (Rus.) // " Soviet Photo ": magazine. - 1982. - No. 7 . - S. 41-42 . - ISSN 0371-4284 .
- R.V. G. Hunt. Color reproduction / A. E. Shadrin. - 6th ed .. - St. Petersburg. , 2009 .-- 887 p.
- Huble A., Grebe L., Wall E. Color photography. - M., Gizlegprom, 1933.