Background
Initially, the term " solarization" was used to describe the effect observed in cases of extreme overexposure of the photographic film or plate in the camera. The effect generated in the dark room was then called ''pseudo-solarization''. Spencer defines the Sabattier effect as: "Partial image reversal produced by brief exposure to white light of a partly developed silver halide image". Many other ways of chemical and actinic radiation "exposure" can be utilised for the partial image reversal. The use of chemicals for image reversal is also known as 'chemical fogging'. ''The SPSE Handbook of Photographic Science and Engineering'' describes the effect as follows: If a film that has been exposed, developed, and washed but not fixed is given a second uniform exposure and developed again, an image with strong border effects is obtained, which combines the original image with a reversed (positive) image. Another usable definition is by Wijnekus & Wijnekus: If an exposed, incompletely developed, and washed, but not fixed film is given a second uniform exposure and developed again, a reversal of the original image may be obtained. The reversal may be partial or complete, depending on the relative magnitude of the first and second exposures.History
The ''Pseudo-solarization'' effect was described in print by H. de la Blanchère in 1859 in ''L’Art du Photographe''. It was described again in 1860 by ''L.M. Rutherford'' and ''C.A. Seely'', separately, in successive issues of The ''American Journal of Photography'', and in the same year by ''Count Schouwaloff'' in the French publication ''Cosmos''. French scientist Armand Sabatier published 26 October 1860 a process of obtaining direct positives (referencing Count Schouwaloff and Poitevin), but according to the description, this process did not seem to have any connection with the Sabattier effect as no mentioning was made of any exposure of the collodion plates after development had started. The name of the author was erroneously spelled with double "t" and thus the effect is hence known as the Sabattier effect in most literature. Sabatier described correctly the phenomenon in 1862. However, Sabatier could not find an explanation for the phenomenon. The effect was usually caused by accidentally exposing an exposed plate or film to light during developing. The artistExplanation
Whereas many photographic effects have been researched and explained in such a way that most researchers agree upon them, the Sabattier effect does not belong to that group. In general the following facts are accepted by the community of photographic researchers: * The assumption that the Sabattier effect can be attributed to the Solarization effect can be overruled. * The opinion that the Sabattier effect is a direct "print-through" effect of the silver produced by the first development on the below situated layers can not suffice to explain the effect. It has been shown that exposing a photographic layer through the base also displays the Sabattier effect. Moreover, chemical fogging is also proof that copier effect is only marginal in producing the Sabattier effect. * Oxidation products produced during the first development at the developed grains cannot cause a desensibilisation of the unexposed grains. * It is difficult to envision that the silver produced during the first development has a desensibilitating influence on the first developed grains. However this point must be further researched. * Although with commercial photographic materials the speed of development of the latent image of the second exposure is greater than that of the first development, it cannot be the determining factor for the Sabattier effect. * Several researchers assume that the development of a latent interior image as result of the first exposure thus affecting negatively the surface "specks" (also known as latent image centers) caused by the second exposure can partially explain the Sabattier effect. One of these researchers, Dr. K.W. Junge, published an explanation for the Sabattier effect as follows:In the darkroom
Agfacontour Professional Film
In 1970, Agfa marketed Agfacontour Professional Film, which simplified the process of obtaining consistent results for images that looked similar to pseudo-solarized images and therefore it was widely used in equidensitometry and art.Agfacontour Professional in der Photographik, Agfa-Gevaert AG Druckschrift Nr. 151 (in German)Agfacontour Professional in Wissenschaft und Technik, C. Sauer, Agfa-Gevaert AG Druckschrift nr. 152, 1. Auflage 1974 (in German) This special purpose film addressed the uncertainty of pseudo-solarisation results. As of 2002, Agfacontour Film was no longer being produced.In digital media
Early video synthesiser technologists concerned themselves with achieving arbitrary curves not limited by film chemistry. A goal was to extend the range of pseudo-solarization effects possible to a computer specified curve. They then applied the defined solarization curve to real time video images. A video lookup table was often used to implement this. Using this enhanced solarization technology, still photos could also be passed through a grey scale or colour lookup table with the advantage that the effect could be previewed and progressively improved, instead of a procedure based on darkroom exposure calculations applied on a one time basis to a volatile light sensitive film or print, as described above. This was an especial advantage for creating colour solarizations with 3 primary colours. Graphs describing pseudo-solarization curves typically place input range of tones on the x axis, with black at 0 and white to the right, and the output range of tones on the y axis with black at 0 and white up. A curve then defines the input to output mapping. Manipulating custom curves in photo-editing programs such asReferences
*Langford, Michael. ''The Darkroom Handbook''. New York: Dorling Kindersley Limited, 1981. p. 236–243.External links