I'm using b&w film. What effect would I get if I layer a red filter and a polarizing filter while photographing snow?
Red filters affect subjects in the blue-green color range, rendering them darker than normal when shooting B&W film. Polarizing filters affect (by darkening as above) polarized light such as is found in clear daylight skies and certain reflections.
The filters mentioned above would render similar results on digital. The filters manipulate light before it passes through the lens and not after it hits the film or sensor.