I've been shooting Maco ir 820/Efke 820 with an 89b and i've made the switch to a #87 filter. I can't find info on exposure times. I know, i should test a roll of 120 and go from there but i don't have time. I'll be shooting 4x5 and 8x10 so longer exposures are the norm for me. How about spot metering w/o filter at iso 3 or 6?