I think these types of arduino testers are great for seeing if your camera needs a service. To see if your old camera is in the ballpark or way out. But if you are actually servicing cameras, you need a tester that will tell you a little bit more about how the shutter is performing.
Focal plane shutters
The first thing to get in spec when servicing a focal plane shutter are the curtain travel times. All of the other shutter timing assumes a spec'd curtain speed and if that's not accurate, it's nearly impossible to get all of the shutter speeds firing correctly. You don't want to be adjusting the slit width before confirming that your curtain times are correct. So you need a shutter tester with multiple sensors so it can calculate travel times across the frame and also variation in exposure across the frame.
The other thing to be aware of with focal plane shutters is the penumbra effect. The curtains essentially cast a shadow on the film, and the optical sensors of the shutter tester are triggering on the edge of that shadow. The transition from dark to light. But if the sensor is too far from the curtains, the edge of the shadow becomes diffuse. It's no longer a sharp edge but a gradient, and the point at which the sensor transitions from off to on becomes uncertain. At slow speeds, this isn't a big deal. But at high speeds, when the slit width is just a few millimeters, this can introduce significant errors.
Leaf shutters
Leaf shutters take a certain amount of time to open and close. Usually around 1 millisecond. Again, this is not a big deal at slow speeds, but at high speeds it makes up a significant portion of the exposure time. While the shutter is opening, the film is not getting full exposure, so camera makers lengthen the time of the shutter action to get a proper equivalent exposure. In the video you measure a Yashica Mat set at 1/500. The tester measured 1/260 but that is doesn't mean that it's a stop slow. It's actually pretty close to where it should be. Here's a link to some info that goes into more detail on shutter efficiency.
https://learncamerarepair.com/downloads/pdf/NatCam-Shutter-Test-Guide.pdf
This isn't meant to be a take down. I think testers like the one you've built have their uses. I just want people to know their limitations as well. When I built my arduino tester I found that it's pretty simple to make a
working shutter speed tester, but it's quite difficult to make a
good shutter speed tester. I eventually discovered
this tester, which is essentially a recreation of a classic camera technician's unit and gladly paid Srozum for all their hard work. It's incredible.
Post #1 by SilverDog
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