View source for Sabattier effect

{{Short description|Photographic tone reversal technique}}
{{redirect|Pseudo-solarization|the original overexposure effect|Solarization (photography)|other uses|Solarization (disambiguation)}}
{{confused|Sabatier reaction}}
[[File:Pseudo_Solarisation.jpg|thumb|Pseudo-solarization of paper positive in darkroom]] 
{{Alternative photography}}
The '''Sabatier effect''', also known as '''pseudo-solarization''' (or '''pseudo-solarisation''') and erroneously referred to as the '''Sabattier effect''', is a phenomenon in [[photography]] in which the image recorded on a [[Negative (photography)|negative]] or on a photographic print is wholly or partially reversed in tone. Dark areas appear light or light areas appear dark. [[Solarization (photography)|Solarization]] and pseudo-solarization are quite distinct effects. Over time, the "pseudo" has been dropped in many [[photographic darkroom]] circles and discussions,<ref name="DPS">{{cite web |url=https://digital-photography-school.com/the-Sabattier-effect/ |title=The Sabattier Effect |last=Guyer |first=Jeff |date=24 September 2013 |publisher=Digital Photography School |access-date=2019-01-09 }}</ref> but the effect that is meant is the Sabattier effect and not the solarization by extreme overexposure.

==Background==
Initially, the term "[[solarization (photography)|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<ref>{{cite book |title=The Focal Dictionary of Photographic Technologies |last= Spencer|first=D A |year=1973 |publisher=Focal Press  |isbn=0-240-50747-9 |page=539 }}</ref> 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<ref name=ThioSol>{{cite web |last1=Buffaloe|first1=Ed|title=Duo-tone Border Depletion Solarization (thiosulfate solarization)|url=http://unblinkingeye.com/Articles/ThiosulSol/thiosulsol.html |publisher=Unblinkingeye.com|access-date=19 December 2015}}</ref> and actinic radiation "exposure" can be utilised for the partial image reversal.<ref>{{cite encyclopedia |encyclopedia=The Focal Encyclopedia of Photography |page=1313 |title=Sabattier Effect |date=1976 |edition=Desk |publisher=Focal Press Ltd. |location=London }}</ref> The use of chemicals for image reversal is also known as 'chemical fogging'.<ref>{{cite book |title=The Focal Dictionary of Photographic Technologies |last= Spencer|first=D A |year=1973 |publisher=Focal Press  |isbn=0-240-50747-9 |page=248 }}</ref> ''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.<ref>{{cite book |title=The SPSE Handbook of Photographic Science and Engineering |last= Woodlief|first=Thomas Jr. |year=1973 |publisher=John Wiley & Sons Inc.  |isbn=0-471-81880-1 |page=428 }}</ref> 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.<ref>{{cite book |last1=Wijnekus |first1=Franciskus J.M. |last2=Wijnekus |first2=E.F.P.H. |url=https://books.google.com/books?id=VQghBQAAQBAJ |title=Dictionary of the Printing and Allied Industries |edition=2 |publisher=Elsevier Science Publishers B.V. |location=Amsterdam  |date=22 Oct 2013 |page=514 |isbn=978-0-44442-249-1 |quote=Sabattier effect }}</ref> 

[[File:Pier study straight.jpg|thumb|right|250px|Normal print]]
[[File:Pier study solarised.jpg|thumb|right|250px|Pseudo-solarized print from the same negative]]

==History==
The pseudo-solarization effect was described in print by [[Pierre_Moulin_du_Coudray_de_La_Blanch%C3%A8re|H. de la Blanchère]] in 1859 in ''L’Art du Photographe''.{{cn|date=January 2019}}  It was described again in 1860 by L.M. Rutherford and C.A. Seely,<ref>''American Journal of Photography and the Allied Arts and Science. New Series'', New York II (1860), page 251</ref> 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 [[Alphonse Louis Poitevin|Poitevin]]),<ref>{{cite web |url=https://babel.hathitrust.org/cgi/pt?id=hvd.32044039119557;view=1up;seq=300 |title=Bulletin de la Société française de photographie 1860 |language=fr |publisher=Hathi Trust Digital Library |date=1860 |quote=pages 283 and 312 }}</ref> but, according to the description, this process did not seem to have any connection with the Sabattier effect as no mention was made of any exposure of the collodion plates after development had started.<ref>{{cite web |url=https://babel.hathitrust.org/cgi/pt?id=hvd.32044039119557;view=1up;seq=300 |title=Bulletin de la Société française de photographie 1860 |language=fr |publisher=Hathi Trust Digital Library |date=1860 |quote=page 306}}</ref> The name of the author was erroneously spelled with double "t" and hence the effect is known as the '''Sabattier effect''' in most literature.<ref>{{cite book |last1=Woodlief |first1=Thomas Jr. |title=SPSE Handbook of Photographic Science and Engineering |editor-last=Carroll |editor-first=Burt H. |location=New York |publisher=John Wiley & Sons Inc. |year=1973 |page=428 |isbn=0471818801 }}</ref><ref name="Frieser">{{cite book |last1=Tomamichel |first1=Franz |title=Die photographische Empfindlichkeit |chapter=8.5.3. Sabattiereffekt und Innenbildumkehr |volume=3 |editor-last=Frieser |editor-first=Hellmut |editor2-last=Haase |editor2-first=Günter |editor3-last=Klein |editor3-first=Eberhard |work=Die Grundlagen der photographischen Prozesse mit Silberhalogeniden |location=Frankfurt am Main |publisher=Akademischer Verlagsgesellschaft |year=1968 |pages=1200–1206 |id=in German }}</ref>  Sabatier described the phenomenon correctly in 1862.<ref>''Bulletin de la Societé Francaise de Photographie'' 8 (1862), page 175, 289</ref><ref>''Le Moniteur de la Photographie'' 2 (1862), pages 27, 45, 50</ref> However, Sabatier could not find an explanation for the phenomenon.<ref name="Frieser"/>

The effect was usually caused by accidentally exposing an exposed plate or [[film]] to light during [[Photographic developer|developing]]. The artist [[Man Ray]] perfected the technique, which was accidentally discovered in the darkroom because of fellow artist [[Lee Miller]] accidentally exposing his film in the darkroom.  It is evident from publications in the 19th century that this phenomenon was "discovered" many times by many photographers, as it tends to occur whenever a light is switched on inadvertently in the darkroom while a film or print is being developed.

==Explanation==
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:<ref name=Frieser/>
* 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|latent image centers]]) caused by the second exposure can partially explain the Sabattier effect. One of these researchers, K.W. Junge, published an explanation for the Sabattier effect as follows:<br>The photographic material suitable for pseudo-solarizing should have a very low tendency to produce surface specks. This is usually achieved by prohibiting the chemical maturity during manufacturing. <br>During the first exposure therefore almost only internal grain specks are produced. The first development will destroy the tendency to produce internal grain specks so that after the second exposure also grain surface specks are produced. These are only produced on grains which have still no internal grain specks. The reason for this is that during the second exposure electrons emerge which are much faster caught by the stable and big internal grain specks than they can serve to build new and smaller surface grain specks. <br>The second development in a surface developer will now attack those grains which remained unchanged by the first exposure so that an image reversal will occur. The fact that instead of a second exposure electron donating systems (e.g. chemical fogging) can be added to the second developer supports this theory.<ref name="Teicher">{{cite book |last1=Junge |first1=K.W. |title=Grundlagen der fotografischen Chemie |chapter=1.8.1.9. Sabattiereffekt |edition=6 |editor-last=Teicher |editor-first=Gerhard |work=Handbuch der Fototechnik |location=Leipzig |publisher=VEB Fotokinoverlag |year=1974 |pages=76–77 }}</ref>

==In the darkroom==
[[File:1981-fotozirkel-kulturbund-eberswalde-by-RalfR-21-sol2.jpg|thumb|Pseudo-solarization of paper positive in darkroom]]

Careful choice of the amount of light used and the precise moment in development to provide the additional exposure gives rise to different outcomes. However, pseudo-solarization is very difficult to manage to yield consistent results.

As a guide, an exposure of one second to a 25 watt [[incandescent light bulb|incandescent lamp]] at two metres distance at around the end of the first minute of a 2-minute development can produce acceptable results. If the exposure is made with the developing print still in the tray of developer, it is important to stop agitation at least 10 seconds prior to exposure to allow any bubbles on the surface to disperse and to ensure that the print is lying flat. Pseudo-solarizing colour prints is more difficult because of the more careful control of temperature and timing that is required and because most amateur processing is undertaken in a processing drum rather than a dish. As lightsource also an enlarger without negative in the carrier can be used.{{better source needed|date=May 2019}} In colour photography, different coloured lights can be used to affect pseudo-solarization, but the results become even less predictable.

Using the Sabattier effect it should be obvious that it is very difficult to manage all parameters for yielding consistent and predictable results and therefore other means have been pursued such as [[#Agfacontour|'''Agfacontour''']] and special pseudo-solarizing developers<ref>Applied Photography, Arnold et al., Focal Press, page 428</ref><ref name="Warren">{{cite patent |inventor-last=Yurow |inventor-first=Harvey Warren |publication-date=1999-07-19 |title=Photographic developer for direct production of equidensity images on a high contrast film |issue-date=2000-07-04 |country-code=US |patent-number=6083671 }}</ref>

In scientific photography it was observed that when using photographic films with very high contrast (also known as lith films), the image produced by the Sabattier effect exhibited a multitude of lines of various width, representing a specific amount of exposure within a certain range. This led to the use of the Sabattier effect in the fields of [[photogrammetry]] and [[equidensitometry]].

==={{anchor|Agfacontour}}Agfacontour Professional Film===
In 1970, [[Agfa-Gevaert|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.<ref>Agfacontour Professional in der Photographik, Agfa-Gevaert AG Druckschrift Nr. 151 (in German)</ref><ref name="Agfacontour wiss.&tech">Agfacontour Professional in Wissenschaft und Technik, C. Sauer, Agfa-Gevaert AG Druckschrift nr. 152, 1. Auflage 1974 (in German)</ref> This special purpose film addressed the uncertainty of pseudo-solarisation results. 

As of 2002, Agfacontour Film was no longer being produced.<ref name="Yurow">{{cite web|last1=Yurow|first1=Harvey W.|title=A Novel Approach to Equidensity Photographic Images|url=http://unblinkingeye.com/Articles/Yurow/yurow.html|website=Unblinking Eye|access-date=28 February 2016}}</ref>

=={{anchor|Digital}} In digital media==
{{refimprove section|date=September 2016}}
Early [[video synthesizer|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 [[CLUT|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 as [[Photoshop]] provide tools to mimic the Sabattier effect in digital image processing.<ref name="DPS"/> [[File:Spiritual_Tree_dsc06786_duo_nevit.jpg|right|thumb|360x360px|A digitally pseudo-solarized color image]]

==References==
{{reflist|30em}}

*Langford, Michael. ''The Darkroom Handbook''. New York: Dorling Kindersley Limited, 1981. p.&nbsp;236–243.

==External links==
*[http://unblinkingeye.com/Articles/Solarization/solarization.html Unblinking Eye - Controlling the Sabatier Effect]

{{Photography}}
[[Category:Photographic techniques]]
[[Category:Science of photography]]
[[Category:Photographic techniques dating from the 19th century]]