This is a useful addition. I may have to buy one as lately I've been rebuilding Zorki and Fed cameras and need to test the curtains at the beginning and end of travel. I built a tester a few years ago but it's always been somewhat suboptimal - at slow speeds it seems OK but at speeds greater than 1/250 the audio signal becomes stretched out and it's harder to pick the onset and offset of the signal.
Originally Posted by AgX
I think part of the problem is that I put the phototransistor inside the box - I should have put it outside the box so the light is not diffracted by the plastic.