This would be a special mode just for measuring relative density changes across the projected negative. You would switch to it from the same selection system used to toggle between "Printing" and "Calibration."
Basically it keeps track of the lightest area measured, then shows a density reading relative to that as you meter across the image. This would be a fairly simple thing to implement, and would not require keeping track of any state beyond the lowest and most recent measurement.
This would be a special mode just for measuring relative density changes across the projected negative. You would switch to it from the same selection system used to toggle between "Printing" and "Calibration."
Basically it keeps track of the lightest area measured, then shows a density reading relative to that as you meter across the image. This would be a fairly simple thing to implement, and would not require keeping track of any state beyond the lowest and most recent measurement.