One of the things about shooting film vs. digital is digital's ability to allow you to change the sensor's sensitivity to light, or it's ISO rating. Shooting in bright sunlight? Drop the ISO to 100 or 200. Shooting in a dark building? Raise it to 1600 or 3200 (or more, with the high-end cameras offering fantastic-looking images at very high ISOs).
Film is of course rated at different sensitivities as well, usually known as the film's speed. The higher the speed, the higher the ISO, the more sensitive to light. Kodak's Tri-X, which is what I'm using for my frame-a-day series currently, is normally a 400 speed film, but I'm shooting it as if it were ISO 3200, basically underexposing it by 3 stops. The long processing time in a highly-dilute developer allows me to get scannable images off the film.
But, I have to shoot everything on the roll as if it were ISO 3200. Which is fine when I'm indoors, but outdoors during the day, that's just too bright. How do you solve that problem, since I cannot change the film's ISO on the fly?
The answer is the use of filters, pieces of glass that screw onto the camera lens for a variety of effects. In this case I used a red #25 filter, a deep-red filter. Using a #25 cuts your exposure by 3 stops, effectively dropping my film back to ISO 400- perfectly manageable even on a bright day.
The downside to using it is that contrast is pushed way up, as the shadows- normally lit by the blue sky- are darkened. This isn't a bad effect, per se, but it is one you have to keep in mind when you are shooting with it. For Christmas I received a 2-stop neutral-density filter, which reduces the light entering the camera by 2 stops. Unlike the red filter, the ND doesn't have any sort of color cast, so it won't have any effect on the scene's contrast, and I will be able to use it with color film as well.
Happy new year, everybody, and here's looking forward to a great 2011!
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