Push Processing for Digital

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Today’s Question: While I never actually did it, I know it was possible to “push” process film captures to get a higher effective ISO. Is such an approach possible with digital?

Tim’s Quick Answer: While push processing in the traditional sense is not possible with digital captures, a similar result would be achieved by simply raising the ISO setting, or by under-exposing a capture and brightening the image in post-processing.

More Detail: Push processing with film photography involved under-exposing photos and then leaving that film in the developer solution for a longer period of time or at a higher temperature (or both). The result was greater detail and a larger visible grain structure.

Using a higher ISO setting provides something of a digital equivalent to push processing. When you raise the ISO setting on the camera, you’re not truly increasing the sensitivity of the image sensor on the camera. Rather, you are having the camera apply increased amplification to the signal gathered by the image sensor during the exposure.

Increasing the ISO setting therefore involves what is essentially under-exposing the scene based on the actual sensitivity of the image sensor, and then compensating with amplification in the camera. Similar results could be obtained by under-exposing without raising the ISO setting, and increasing the brightness of the image in post-processing. Generally you’ll get better results by raising the ISO in the camera, but the overall effect is similar.

In either case, you’ll get a result that is somewhat similar to push processing with film. It isn’t exactly the same due to the different mechanics involved (chemistry versus digital signal processing), but in concept they are similar.