As a collector of old cameras, I try to fix the ones that arrive home. Many times, even if the camera is working, the shutter speed uses to not to be accurate. To test it I'm thinking on creating a small gizmo to measure the shutter speed and in the case of the SLRs, the speed of the individual curtains, to check if some cleanup/repair/adjust is needed.
The basis is an Arduino Mini Pro board. Five phototransistors will allow to measure all the shutter types: centric, vertical sliding and horizontal sliding.
A pushbutton will allow to reset the session. After a reset, at every time a shot is detected the different travel speeds will be measured. In the same session (same shutter speed) several subsequent measures will be taken, stored and averaged. The display will show the current measures, the number of measures taken so far and the average so far.