OK, I've got my little tester working. Tuns out I needed 6 volts. So now we have here a screen shot of an actual shutter test--I forgot which speed, but it's not important for now. My problem in interpretation. I'm dealing with a 100 year old Betax shutter that I worked on, and I knew all along that I had a rather week shutter-closure spring. If you will note the attached shot, you will see that after the initial exposure, there is an equally long time before the graph returns to zero, which I am supposing to be caused by the slower action of the weak spring. Would you agree, or is this to be expected? And if so, should I include some portion of this slower upward sweep in my computation? Thoughts? Thank you.