I recently read in the Kodak Master Photoguide from 1951, that the camera can be used as an extinction meter.

By focusing on a dark object and stopping down until only slight detail remains, and consulting a chart, an accurate exposure can be made. The chart shows times for Kodak Super-XX, which shows an index of 100, that would be about ISO 200, in today's scale. From what I can find about that film, the reciprocity issues normally associated with longer exposures were virtually nonexistent.

Does anyone have any experience with this? Would only calculating the exposure from the table for your film speed and adding for reciprocity provide a correct exposure? I tried it on my digital, and got decent results.

I just wanted to see what folks have experienced before using up some film. Thanks!