The f-Stop Printing Calculator allows darkroom printers to modify times by stops when calculating exposure values. The calculator will establish 1/4 stop increments (+ or – up to 3/4) of the base time you have entered and, either generate a new time, or an increment of an f-stop if you are burning in. By working with f-stops rather than linear units of time, you can produce an easier to read test strip as the exposure differences are exactly equal. This app has been designed by Digitaltruth Photo Ltd and Bruce Tanner.