As I'm sure you all are aware, film's ISO ratings are simply a guide and certainly not etched in stone.

What I do when I start using a new film is take it and do tests to find just exactly where that film's true ISO is for HOW I SHOOT, eliminating a lot of guessing down the road. And do your tests both WITH strobe and then again with NATURAL light.

Film does react differently to the two whether manufacturers admit to it or not. I rate my films (which are marked 100 ISO) from 50 to 80. Never at 100. And this is based on the film being used to photograph people vs. objects for one, the lab used for processing, and my style of shooting.

Some films I actually give a little "push" in processing where others I simply run normal. All of which you should take into consideration as well when developing your ISO for a particular film stock. Plus, I shoot 99% chrome (slides) with the only negative stock being the new B&W film from Fuji, called Acros. DJM

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