There are three main areas where snow will deceive your camera:
On a bright sunny day, snow can reflect a great deal of sunlight, making it very difficult to obtain contrast against other foreground subjects, especially those which are of a lighter shade. Similarly on an overcast day, the gray, dull sky and the snow too offer very little contrast.
Image courtesy: doortoriver
Exposure is an issue under both overcast as well as bright sunny conditions.
If the day is sunny, the snow would reflect sunlight and appear 1-2 stops brighter than what a routine camera meter expects to see. It feels the frame is over-exposed, and hence, quite un-smartly, compensates by lowering exposure. The result is that the bright snowy scene in front of you transforms into a dull gray scene in your camera. Shot ruined. Similarly if the sky is overcast, the camera meter may not be smart enough to figure out that the snow you're shooting is white snow under dimmer lighting rather than a gray object under proper lighting. And most camera meters go with the latter option and you end up getting gray snow instead of white. The cure here is to increase EV by a stop or so, to get the color of snow correct.
- Likewise, a darker object against the background of a bright snow comes out very dark or underexposed. One has to carefully meter for exposure on the darker object (preferably using spot metering) to prevent the camera from automatically metering the bright snow. Else, lowering EV compensation by around 1 stop should also work. Do take care not to under-expose, else the snow will look gray instead of white.
As a general rule, if using an SLR, use 'spot' or 'evaluative' metering if your snow scene has areas of contrast - dark and bright - in it. But if its more or less evenly bright, 'center weighted average' metering may give you appropriate exposure.
As snow can quite brightly reflect sunlight, you may end up losing surface texture and get a flat, over-exposed image. Try to place your subject at a 45-90 degree angle, to get the surface texture correct. Bright sunlight also tends to upset the white-balance and one ends up getting a bluish cast on the white snow. Manually setting the white balance while pointing to a clean white patch of snow should improve results quite a lot.
Always remember to watch your histogram while shooting snow, and if you're getting blown highlights, reduce exposure, shutter speed or ISO. You may also bracket for exposure and use HDR software to get a truly unique snow photo.