True Film Speed
After attending my darkroom class this week I have decided that in order to obtain the most optimum exposure for my film, I need to test it. We all purchase rolls of film that have a manufacturers ASA film speed (ie. 100, 400, 1000). However, in most instances, the recommended film speed does not accurately reflect the true speed of that film. For instance, there is really no such thing as 3200 speed film as the manufacturer would have people believe. In fact, 3200 speed film may best be shot at speeds closer to 1000 - - unless of course, you are into grainy shots. The 3200 speed assigned by the manufacturer merely means that the film can be "pushed" to 3200 during development. (I won't go into the details of pushing and pullign film - - I will save that for another day).
I am by no means professing that I understand all of the Zone rules. The truth of the matter is the Zone system makes my head hurt. However, my instructor has given me a basic test that I can perform that won't make my head hurth. I simply take a few rolls of film (I typically shoot Tmax 400) and bracket that roll - This means I will shoot 3 frames at 100 speed, 3 at 200, 3 at 320, 3 at 400, etc. I do this a few times, and then process the rolls in the darkroom as if the entire roll was shot at 400 ASA. The result gives me a quick and easy way to decide which prints, shot at a particular ASA, (assuming I develop them the exact same way) look the best. I guarantee that the photos shot at 400 ASA will not necessarily be the best.
We all shoot differently, our cameras all have different meters. I may tend to over or under-expose my shots. This test will ultimately give me a way to know how my camera should be set when I use Tmax 400. I may find that I should set my camera to 200 to get my best results, even though the manufacturer is telling me to set my camera to 400.
If you are wondering why I am going through this trouble? I am kind of side-stepping around the intricacies of the zone system and giving myself a way to determine the optimum setting for my film. The general rule in photography is that you EXPOSE for the shadows and DEVELOP for the highlights. By exposing for the shadows we are in essence increasing the detail in the dark areas of the photograph. The Zone System gives you a way to completely control the shadows and highlighted areas of your photograph (in a nutshell). The only way that I can accomplish this is to know the "True Film Speed" of my film.
While I am on the subject of exposure, here's a cool site that calculates your aperture and shutter speeds in different conditions. Most of us do this in our head, but it's kind of neat to see the results quickly as conditions are changed.
10:20:22 AM 
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