Quote Originally Posted by John Koehrer View Post
The ANSI standard is ~30% like it or not. At 500 more like 50%. That;s 1/2 stop either way, a total of one stop.
Adjusting a LF shutter can be pretty tedious. The slow speeds are controlled by the governor itself, clean it, lube it. and by the POSITION of the governor relative to the retard lever that it engages.
High speeds can be adjusted by replacing main springs or swaging/filing sections of the speed cam. suggesting this is a simple thing doesn't suggest familiarity with the work.
Adjusting a metal plate requires a calibrated hammer & punch and filing can be one stroke +/- sorta.
So can wasting 8x10 transparency film at $20+ per sheet.

The first step in calibrating a shutter is to get everything clean so you can inspect each part for wear/damage, damage can sometimes be from the last one to work on it. After correcting these faults, put it together and see how it times, usually it's much better. If the shutter has been run long without proper lubrication and/or dirt in the mechanism, there will be wear in the slow speed governor and other areas. Trying to calibrate the shutter without rectifying this wear is pointless.

Once you get the slow speeds timed, check the faster speeds. By tinkering with the cams (swage if neccesary then use a medium India stone if neccesary) (don't change springs, you'll have to starrt all over again), you can get all but the highest speed very close to the marked speeds. The top speed will be slower than marked, the larger the shutter the more discrepancy.
What is very important is to get the speeds to be consistent. This requires cleanliness and proper lubrication. The above assumes you are working on a fairly recent Copal or Compur shutter, older and pneumatic shutters require slightly different approaches. You have to understand exactly what you are doing and why, otherwise you'll not get an accurate shutter.