Exposure time varies greatly by exposure unit. With our Autolight Exposure Unit, start with 60 seconds on the first exposure and 60 seconds on the second exposure (film positive)
Exposure time depends on the quality of film positives. Pass a white paper behind the film positive. If you can detect the edge of the paper behind the emulsion, your positive is somewhat transparent and will require reduced exposure times. In a good positive, no light should be seen through the black part of the film.