Pushing ISO

Hello all,
I was watching a TV show last week and they were interviewing a photographer from Montreal who photographs using ISO 400 slide film then "pushes it" to ISO 100. What does changing the ISO of the film do to the photo? What effect is gained by this method? Is this a common method?

Quote:

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Originally Posted by Aranha

Hello all,
I was watching a TV show last week and they were interviewing a photographer from Montreal who photographs using ISO 400 slide film then "pushes it" to ISO 100. What does changing the ISO of the film do to the photo? What effect is gained by this method? Is this a common method?

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You are actually reffering to pulling the film. Pushing means to shoot film at a HIGHER ISO than it's rated, pulling is shooting it at a LOWER ISO.

So shooting 400 ISO at 800 is pushing it, shooting it at 100 is pulling it. Pushing lets you get exposure settings that you would with higher ISO film, but you have to make sure you tell the developer how much you pushed it, they need to develop appropriately to compensate. Pushing increases grain and contrast. Pulling on the other hand reduces contrast. Some people pull film in direct sunlight to help reduce contrast. I don't know the effect of pulling on the grain appearance of the film though. Just like with pushing, the real step happens during developing, so you must communicate your settings to the developer.

Thanks very much Seb for clearing up "Pulling" for me. With that information I now understand what the photographer was speaking about. I thought it only had to do with setting the ISO on the camera, and nothing with processing.