Push processing
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Push processing in photography refers to a film developing technique that increases the effective sensitivity of the film being processed.
It is described by Phil Davies as; "To prolong the time of film development in an effort to compensate for underexposure. Also, to underexpose a film a deliberately with the intention of attempting compensation in development."
Push processing involves developing the film for more time, possibly in combination with a higher temperature, than the manufacturer's recommendations. This technique results in over-development of the film, compensating for under-exposure in the camera.
In contrast, pull processing involves over-exposure and under-development, effectively decreasing the sensitivity of the processed film. It is achieved by developing the film for a shorter time, and possibly at a lower temperature.
Push processing allows relatively insensitive films to be used under lighting conditions that would ordinarily be too low for adequate exposure at the required shutter speed. Pushing results in decreased quality: artifacts such as higher contrast, lower resolution, distorted colours, increased grain are often visible on film that has been push processed. This may be deliberately exploited for artistic effect.
When a film's effective sensitivity has been varied, the resulting speed is called the exposure index; the film's speed remains at the manufacturer's indication. For example, an ISO 200/24 film could be push processed to EI 400/27 or pull processed to EI 100/21.
References
pg 373 Photography by Phil Davis/ fifth Edition ISBN 0-697-00300-0
See also
External links
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