Cross processing (sometimes abbreviated to Xpro) is the procedure of deliberately processing photographic film in a chemical solution intended for a different type of film. The effect was discovered independently by many different photographers often by mistake in the days of C-22 and E-4. The process is seen most often in fashion advertising and band photography, and in more recent years has become associated with the Lo-fi photography movement.[citation needed]
Cross processing usually involves one of the two following methods:[citation needed]
* Processing positive color reversal film in C-41 chemicals, resulting in a negative image on a colorless base
* Processing negative color print film in E-6 chemicals, resulting in a positive image but with the orange base of a normally processed color negative
Traditionally, cross processing color slide film in C-41 process chemicals is most common. Some commercial-level photography/darkroom merchants will perform this developing process. However, cross processing can take place in many other forms, such as negative color print film and/or positive color reversal film in a black and white developer.
Other interesting effects can be obtained by bleaching color films processed in black and white chemistry using an hydrochloric acid dichromate mixture or using potassium triiodide (KI3) solution. If these bleached films are then re-exposed to light and re-processed in their intended color chemistry, subtle, relatively low contrast, pastel effects are obtained[citation needed].
Color cross processed photographs are often characterized by unnatural colors and high contrast. The results of cross processing differ from case to case, as the results are determined by many factors such as the make and type of the film used, the amount of light exposed onto the film and the chemical used to develop the film.
Cross processing effects can be simulated in digital photography by a number of techniques involving the manipulation of contrast/brightness, hue/saturation and curves in image editors such as Adobe Photoshop or GIMP; however, they lack the unpredictable nature of regular cross processed images. Some programs, such as online photo editor Picnik even have a cross process function.
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