Quote Originally Posted by Kirk Keyes
Last year, I was in Death Valley, trying to take photos of patterns in the sand. I've got one of those newer Minolta Flashmeter VIs that can do both incident and reflected measurements. I used the spot meter while there and some of the scenes were only about 3-4 stops (reflected) between the darker and lighter portions of the scene. Using Acros and Xtol, I was able to develop the film enough to expand it out to where it prints well.

Today, I was flipping through my copy of the BTZS book (3rd Ed.), and I thought back to the Death Valley stuff. So I was looking for a description of how to meter scenes of low contrast using BZTS. Using an incident meter, it looks to me that the BZTS system can't measure scenes that have SBR's less than 5. It also seems that it can't differentiate between a 5 SBR scene and a 3 or 4 SBR scene.

I know you can determine development times for SBR ranges this low, but how do you actually measure them with and incident meter. Does photographer's discretion (i.e. override meter readings) kick in here?


A couple of things, first a difference in reflected measurements of 3 or 4 stops is very different from measurements of Illuminance. If you have a shadow, however light and a bright "side" you can use the incident system as explained by Davis. OTOH like any metering system it does requires some experience and the situation you describe is a perfect example. There are times when an SBR of 5 just simply wont do, you have to use an SBR of 4 or even 3 and this can only be determined by experience.

All the exposures in the BTZS are based on the shadow measurement, so in the case of a SBR of 3 or 4 you would still use the meter setting given to you by the shadow reading. Supposedly you would have already made your film tests and know how you should adjust the EI for extreme expansion.