Discussion in 'Photography Beginners' Forum' started by quad b, Jun 29, 2006.
What is push processing??
Gooday "quad b" from sunny Sydney. Very simple question. If you shoot a film, and you underexpose it either deliberately or by accident, you can correct the film density by "push processing" Philip.
How would I go about push processing in the darkroom?
Push processing is done with film. When you expose the film in the camera you shoot it at a higher ISO to what it is rated at... so you may shoot a 400 speed film at 3200 ISO. Because this causes underexposure, you must compensate when developing. By developing for a longer time it corrects the density of the negs and gives you printable results even though you shot the film faster than it was meant to be. The main downsides (debatable) are increased grain and contrast. Push processing development times, as well as a heap of useful information can be found here: http://www.digitaltruth.com/devchart.html
You develop the film for a longer period of time than normal. The increase in time depends on how many f stops the film was underexposed. The increase in time is sometimes expressed as a percent of the normal developing time rather than in minutes and seconds. The actual increase in minutes and seconds will depend on the developer and the temperature.
Instead of defining the underexposure in f stops, you can also define it interms of the ISO film rating. If the film is rated at ISO 100 and you underexposed it one f stop, that would be the same as rating it ISO 200. If underexposed two f stops, the ISO rating would be ISO 400. Each reduction of an f stop is the same as a doubling of the ISO number.
As noted above, push processing isn't a something-for-nothing situation. You gain the ability to get a usable negative with less exposure, but the negative will have increased grain and a reduced gray scale. Finally, it's all or nothing. Unless all of the exposures on the film were taken at the same ISO rating, some [those taken at the normal ISO rating] will be overdeveloped.
Push processing is something you resort to when normal exposure and processing will not do the job.
Cool, thanks for everyone's help.
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