Measuring shutter curtain travel time.

The first procedure for adjusting the shutter is to adjust the shutter curtain travel time. To measure the shutter curtain travel time one would need at least 2 sensors a distance apart. My question is for 35mm camera how far is the best distance? Let say for a horizontal travel curtain the width is 36mm but it would be relatively difficult to space the sensor 36mm apart because the edge of the opening may interfere with the sensor. So it should be somewhat less than 36mm but how much is best in your opinion?

For horizontal shutters, I have a pair of diodes on a breadboard where the spacing worked out to 34mm when I mounted them. I've tried 36mm exactly but it makes positioning very finicky. That's close enough too that you can spot issues like curtain bounce and capping.

Of course 36mm would be "perfect" since, at least if you're measuring with a scope like I do, you can measure travel times just by taking the differences between the two signals. If it's a lesser but known distance, the math is easy to take the measured time by the known distance and extrapolate that to 36mm.

Unfortunately there is no standard. Manufacturers often specify the travel time but not the spacing. A common distance is 32mm horizontal and 20mm vertical, that is frame size minus 2mm on each side. You would then tune to match the curtains and for exposure accuracy. One can extrapolate to a different spacing but only up to a certain point because the curtains might be accelerating.

If you look at the service manuals for your cameras, sometimes it will tell how far apart the sensors are.



Other times some guesswork is involved:

Also, Serhiy Rozum has provided an excellent table here: