I often come across film photographers who delight in ‘pushing’ film, that is, setting the ISO settings on the light meter (either the camera’s or a separate meter) to a higher number than the speed of the film being used. So, for example, if Tri-X is being used, the camera’s ISO setting will be set to 800 or 1600, rather than the 400 of Tri-X. Of course, pushing film is a valid technique if you are prepared to accept the consequences as part of an overall artistic approach, but I sometimes wonder whether many photographers fully understand what these consequences are.
For the digital photographer relying on the automatic exposure algorithms built into the camera, setting a higher ISO speed may make perfect sense in certain situations: dim conditions would lead to the camera ‘compensating’ so that either shutter speeds are reduced (leading to blurred moving objects) or lens are ‘opened’ (reducing depth of field). Dialling up the ISO setting allows images to be taken in dim conditions but at the cost of picture artefacts (graininess for example).
But the situation for film photographers is different:
- Firstly, a film photographer is committed to an ISO setting for the whole film, because the compensation required for the exposure during the film development stage has to pertain to all the images on that film (as the film is processed as a whole). Street photographers encounter a very wide range of light conditions in a short time, unlike for example landscape photographers. The correct exposure values on the shady side of a street on a sunny evening can be 4 stops different to the conditions on the sunny side of the street. So to ‘push’ a 36 film roll is unlikely to be right for a street photographer working the whole street.
- Secondly, film manufacturers tend to over-rate box film speeds. Many tests have shown that film box-rated at 400, say, is better exposed at 320, or even 200, say. Quite why this is the case, I don’t fully understand other than to suppose that manufacturers think that photographers prefer to buy higher box speeds.
- Thirdly, for some with manual mechanical cameras, the whole question is irrelevant. I use a film camera with no light-meter, and hence the camera is neither making any compensation on my behalf nor is it indicating a combination of settings to give a ‘correct’ exposure value. The only light meter is my eye. If I am dealing with a very wide range of exposure values, as on bright evening with deep shadows, I have to decide whether to expose for the shadows and let the bright areas fall where they may during film development, expose for the bright areas and let the shade ‘black out’, or travel some happy path between the two. If there is a very big range of exposure values, then I would probably overexpose and under-develop the film to try to tame the range.
- Finally, artistic intention has to play a part, even for street photographers. There is a three-way trade-off between speed, graininess and sharpness. The selection of film type, exposure, developer type and developer time and agitation has a big effect on contrast and how sharp the image appears.
So, I don’t agree with the advice often set out for street photographers to push film (see for example Eric Kim). Sure, if you want that high contrast grainy grundgy look that seems so popular in today’s street photography, then fine, nothing wrong with that. Also, if you are into hyper-focal settings, then fine. But, then you would probable be better off with a completely automatic point and shoot digital camera, as this is really all you are doing with hyper-focal settings.