I have a number of sensitometers to compare. Each is a different construction. EG&G: Xenon flash Wejex: incandescent lamp ESECO Speedmaster: green LED ESECO Speedmaster: blue LED I'm going to run some step wedges at different development times and see if they all produce curves that can give reasonable information about development time. The LED sensitometers are frequently available on ebay and I hope to provide some information on the utility of those devices in making control strips for the B&W home darkroom. Then null hypothesis here is that the color of light and time of exposure will have very little effect on the films response to changes in development times.