
Posted: Sat Mar 09, 2002 6:14 am
Okay, I'm back withg some more odd questions

I recently went to Calumet (the web site) looking for something, and there on the front page was an electronic shutter tester for a very good amount. I couldn't resist, and I don't regret it. It has already served me well after only two day's use. But it raises some questions...
After testing all my shutters, I found them all to be slow but not overly erratic. Taking a chance on the first one, I shot some graphite into the works and the shutter came right up to speed. Did the same to the rest of them and they all came up to speed. I'm happy, almost... There seems to be a problem with speeds over 1/100th or so. The shutter does get faster but the tester doesn't. I verified the tester's accuracy on a 35mm electronic shutter up to 1/1000, and they do agree to about 1%. But not on leaf shutters. Not even on the much newer Mamiya C330 shutters which I know perform very well.
The 'manual' that comes with the tester tries to explain "shutter efficiency" with leaf shutters and says that most have a 1 millisecond travel time. That would be a total of 2 ms to open & close (that's 1/500 alone). And that the shutters are rated for a fully open time. In the example for this they explain .004 second when tested at 1/500. .004=1/250, the difference being the travel time. And this would explain the slow time I get when testing 1/400 on my shutters. They clock in between .007 to .004 (not all get to 1/400). Does anyone have actual experience in testing shutters this way and is there any reliable way to test the fast speeds?
The other question is about fast shutters... After lubricating mine, now many are a bit fast at the slow end. Some come in at 1/3 second for a 1 second setting, getting closer as speeds go up. Can this be adusted? Is it worthwhile? Or should I just mark the fast ones and make up for it with arperture (seems more pratical to me?)?
Well, sorry again for the long post but the subject of leaf shutter testing at the higher speeds interested me a bit and I thought someone else might also be interested, and maybe know some answers