In article , jashiau@midway.uchicago.edu says...

>Can anyone recommend a good filter for bringing out contrast in the
>sky and making clouds more visible? I shoot black and white film and the
>sky in all my pictures are coming out white. Thanks

If your skies are coming out paper-white (no tone), you are probably
overdeveloping the film (or possibly using too high a contrast grade
of paper) - normally, even an overcast sky will show some tone in a
print. IF the sky has VERY clear blue areas, the yellow filters will
somewhat darken the blue areas, but otherwise, you may want to try
an orange filter (or for more extreme effects, a red). Be aware that
camera TTL meters often show reading errors when metering through
the pure colors of B & W filters, and can be off by as much as 1.5
stops. (Meter without the filter, put it on, and apply the needed
compensation; or [beforehand], compare the readings of a grey subject
in constant light without and with the filters you have, note the
differences between what they should be [given the filter factors]
and what they are, and then always apply those compensations with
the filters after taking readings with the camera meter.)
Hope This Helps