[QUOTE=Claire Senft]What methods are you using to determine exposure and SBR, to establish a developing time, with conditions of backlighting?
When working, I used to do a lot of macro work with small sealed glass bottles or test tubes with bacterial or fungal cultures on their specific growth media.
I would meter with the incident hand-held meter pointing twards the polarized light source. Correct exposure was usually 1.5 stops (plus bellows extension, plus 1 and 1/3 for the on-lens polarizer) open from the light meter reading.
In about 20 years, I rarely found this technique to fail.