Solarization (photography)
Solarization (real solarization) is an alienation of the photographic image through strong overexposure. It is not to be confused with pseudo-solarization (actually: Sabattier effect) . The real solarization only affects analog photography , since the effect only occurs with photographic film .
In the literature, the following is generally given as a definition:
If a photographic layer that is suitable for solarization is exposed to increasing actinic exposure, the blackening resulting from the exposure does not increase steadily after development , but reaches a maximum value and is still at stronger exposure again smaller. This decrease in developable blackness despite increasing actinic exposure is called solarization.
phenomenon
Photographic materials show a typical blackening curve . This describes the relationship between the exposure and the resulting blackening, the density , but is also dependent, among other things, on the development conditions. The simplified graphic on the right shows the area of underexposure of a negative film between points A and B , as well as the normal working area B to D. To the right of point D, the light-sensitive layer can no longer adequately implement the further increasing exposure intensity, until finally the maximum at point E. possible density is reached.
If the exposure is increased even further, the effect of solarization occurs: the blackening of the film decreases again. This effect can make extremely bright areas of a photo, often the sun, when it comes into the picture, initially lighter in the negative and then darker in the positive than the surroundings. Examples of this phenomenon are The Black Sun, Owens Valley, California by Ansel Adams , The Black Sun (1955) by Minor White and the series 1h (2005–2010) by Hans-Christian Schink .
Explanatory models
Solarization was already known to Daguerre and is probably one of the earliest known phenomena in photography . John William Draper was the first to call the effect "solarization". 1840 already watched JWF Herschel that through strong overexposure of a reversal of the picture negative to positive can be done. Also NMP Lerebours observed this phenomenon in 1842 (without that he realized what it was) when he a daguerreotype of the sun created. The result was considered unsatisfactory because the sun disk (the sun image on the daguerreotype plate) was overexposed and solarized. In 1843 L. Moser reported: "... that the light in the camera obscura delivers the negative image that has been known for a long time; if the light continues to work, the image changes into a second positive one ... and in recent times I have Has already received the third picture a few times, which is negative ". This was confirmed in 1880 by Janssen, who received the repetition of the solarization phenomenon in the strongest sunlight. In 1857 the solarization was described by William Henry Jackson, whereby the extreme overexposure caused an exact reversal of the chemical processes. The photo pioneer Hermann Krone also recorded the apparent course of the sun in 1888. In the digital photography solarization does not occur. In addition, the solarization effect is largely suppressed with technologically modern film material. The desired blackening of the sun line can be achieved through a long exposure , but the landscape can usually only be seen vaguely.
In the literature two theories were initially discussed, the re-halogenation theory or regression theory and the coagulation theory. According to the re-halogenation theory, the silver nuclei develop back into silver halide when overexposed and lose their ability to develop . This process can be repeated several times, so that the blackening curve can have several peaks. The solarization can be canceled by a halogen acceptor, which speaks for the theory. This is in contrast to the theory of coagulation, with which the effects of light intensity and double exposure effects are compatible. “The coagulation theory is based on the idea that the germs only act as developmental germs up to a certain size. With stronger exposure (solarization area) they coagulate to form larger structures that no longer act as a latent image. ”In 1929 H. Frieser speculated about the possibility of bromine atom migration in the form of defect electrons.
The phenomenon of solarization is still not fully understood, but it is widely believed that coagulation and re-halogenation are responsible for it. However, recent attempts lead to the occurrence of a latent image lying in the grain interior as the cause of the occurrence of the reverse effect. This latent image is evidently a much more effective trapping point for the latent image that occurs at a later point in time of the exposure than the frosting seeds of the crystal surface are. It is also assumed that re-halogenation theory and coagulation theory interact.
Individual evidence
- ↑ a b c d e Franz Tomamichel: Photographic effects through the dismantling of a latent image . In: Volume 3: The photographic sensitivity (= Hellmut Frieser, Günter Haase, Eberhard Klein [Hrsg.]: The basics of photographic processes with silver halides ). Akademische Verlagsgesellschaft, Frankfurt am Main 1968, OCLC 310490074 , p. 1217-1232 .
- ^ The Black Sun, Owens Valley, California
- ↑ The Black Sun (1955)
- ↑ 1h (2005-2010)
- ↑ a b Eder: LXIX. Photographic Analysis of Movement by Janssen and Marey . In: History of Photography . Dover Publications, Inc., New York 1972, ISBN 978-0-486-23586-8 , p. 506.
- ^ François Launay: The Method of Stellar Circles . In: The Astronomer Jules Janssen . Springer, New York Dordrecht Heidelberg London 2012, ISBN 978-146140-697-6 , p. 116 (accessed January 8, 2019).
- ↑ Cf. Martin Hochleitner, 1h - An introduction to a photographic project by Hans-Christian Schinks, in: Schink, Hans-Christian, 1h, Ostfildern: Hatje Cantz, 2010, pp. 6–9. Here: p. 6.
- ↑ a b cf. Hans-Christian Schink in conversation with Dorothea Ritter, in: Schink, Hans-Christian, 1h, Ostfildern: Hatje Cantz, 2010, pp. 82 - 87. Here: p. 82.
- ↑ Cf. Ewald Gerth, Analytical representation of the kinetics of the germ build-up in the photographic process, 1971, pp. 83f.
- ^ J. Egger, E. Klein, E. Moisar, The behavior of strongly solarizing layers with a combination of short and long exposure, in: Journal for Scientific Photography, Leipzig: Barth, Vol. 57, 1963, pp. 132-143. Here: p. 143.
- ↑ Cf. Ewald Gerth, Analytical representation of the blackening curve taking into account the Schwarzschild effect, in: Journal for scientific photography, Leipzig: Barth, Vol. 59, 1965.
