Quote Originally Posted by Bill Burk View Post
Hi Tom1956,

The vendor's chart you found seems to illustrate three different products they offer, which seem to be designed to peak at different colors.

The reference I found in Todd-Zakia Sensitometry gives a single CdS curve, probably an average of cells available at the time, that is a little less abrupt...

Hi, I don't know if Todd and Zakia told what the (RCA) S-3 and S-11 are, but the designations sound like they may be photomultiplier tubes. If so, they would have been more at home in an densitometer from that time period than in a hand-held exposure meter.

All of those sensors could have had their response manipulated just about anywhere with filters, so one should keep in mind that an actual exposure meter might not respond the same as the sensor data indicates.