Quote Originally Posted by kavandje View Post
OK, hypothetical: Big landscape, early morning just after sunrise, no clouds, facing west into valley, light fog covering the floor. Tentative guess at exposure?
IR at sunrise? Yikes, that's a hard call, especially if there is ground fog. I'd go with EV+8 or so at least, but I'd also definitely expose two sheets and keep one in reserve should major processing adjustments be necessary.

At sunrise I think you might do better with a deep red filter and EV+2 or 3. There probably won't be much IR component at all until mid morning. The optimal IR hours (i.e. when exposures are shortest and the Wood effect is at its strongest) are typically from about 11 am to 3 pm in most places; maybe in dry desert you might extend that by a couple of hours, but even in the desert, when the sun is low it scatters through all kinds of moisture on the horizon.

P.S. Yes, by "EV+8," I mean an 8 stop filter factor. So in sunny 16 light, rating the film at 400 and shooting at f/16, the normal exposure would be 1/400 and the exposure with the IR filter would be ~1 sec. With exposures longer than that, you are quickly getting into reciprocity issues and will find yourself doing exposures of 30 sec or more!

P.P.S. I miss the baobabs! I grew up around them. Thanks for that link!