by pgillis » Sep 26, 2005 10:33 am
To eliminate fog, the glass must be warmer than the air (or more precisely, warmer than the dewpoint temperature.)
I have found that pressing my tongue against the glass for 10 seconds or so will do the trick. Then of course you need to wipe off the saliva with a very clean cloth or tissue (often a precious commodity!) Then the glass will generally stay clear for a few minutes.
Of course it is best to do this to a filter in front of the lens--wiping the lens itself in-cave risks scratching it.. But if there is dust or grit on the glass, and it cannot be blown off, I think licking it off is probably safer than trying to wipe it off. But I don't think it is very nutritious!
Paul Gillis
Falls Church, Va.
Creaky old flashbulb & film burner
PSC, NSS, GVKS