Jeremy Jackson , Feb 03, 2010; 09:10 p.m.
Hi Maryanne, to capture snow falling as a single flake (not a blurred streak), you'll need at least 1/120th of a second. 1/250 is getting ideal. Aperture does matter somewhat. The larger your DOF, the more snow flakes you will see clearly defined. The more snow flakes you see, the busier the image will get. So, for example, f22 will give you a very snowy, busy image. F2.8 will blur most of the snow so you will not see very many flakes clearly defined.
What I would do is experiment with different apertures to see what looks nice. Then choose the lowest ISO for the aperture you want so that you can have at least 1/250th. Start at ISO 800 and if you can get away with less then go down.
If you want to see the snow at night a flash is the only viable, easy method. But very finicky.
This is one instance where the ability to quickly see your results is very, very useful. The wonders of digital. Cheers, JJ