In article , djlb@st-andrews.ac.uk says...

>I heard that when shooting in snow, one has to stop down to compensate for
>the metering, or obtain an exposure lock from a midtone. I'd be grateful
>if someone could inform me as to the truth in the above.

Since the meter doesn't know what is in front of it (white, black, or ?),
it turns that subject-whatever-tone into a medium tone on film (as it was designed to do) - and snow is underexposed to a grey. The best way for me
to meter a snow scene is to meter only snow (in the general direction of
the intended photo), and open up 1 1/2 to 1 2/3rds stop from the indicated
exposure (to move the grey snow reading to a much lighter grey in the photo).
Hope This Helps