A Stouffer scale is a piece of film that has been exposed to different densities from clear to a solid black. To use it you will need to lay the scale over the film and expose the film thru the scale. Some how you read the scale on the film and then you are able to figure out the exposure. I would be lying if I said I knew anything else about the scale. The old time printers (offset) would use a shorter scale from Stouffer that was on a piece of paper. You would expose and develop the line film for a "solid 4". In theory, everything below 4 would be black and everything above would be white. That is all that is needed in line film processing. I would just make a test strip and be done with it.