Shutter Tester

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Cuchulainn

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Brian
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I've been working on an Isolette that I picked up cheap off eBay. It's shutter was firing, but I wanted to test it with a bit more accuracy. I had a play today with the new Raspberry Pico. For those who like to play around with electronics, it's more like and Arduino than a Raspberry Pi - it's a small standalone computer that had a lot of inputs and outputs to connect to sensors, electronics, motors etc. It's also cheap - it costs about £4 and easy to programme in Python.

So, a few hours learning how to do some things, a phototransistor and a resistor later and I have a shutter tester that seems to work up to at least 4kHz. The picture and video below show it mounted in a board that includes a screen and some other nice things because I'm testing the Pico for work (and costs about £20, so still reasonably prices), but the whole tester could be built on breadboard and give the results back to a PC or laptop without needing this extra hardware. Oh, and the shutter seems close enough for a 60-something camera that I'm not going to open it up!

Pic:
ShutterTesterPicoWeb.jpg


And there's a video of it in action here:
Shutter Tester with Raspberry Pico
 
Cuchulainn said:
It's genuinely easy to set up once it's been done once. Would be happy to tell people how and share the code if anyone needed it! Helps to be able to solder.
Click to expand...
Alternatively, start mass production with a 95% reduction in price to your friends here in f&c :hug::p:LOL:
 
I'd be very interested in more detail on this - I'd not heard of the pico but looking at the photo, it does look fairly straightforward as you say. Nice job.
 
Lindsay56 said:
I'd be very interested in more detail on this - I'd not heard of the pico but looking at the photo, it does look fairly straightforward as you say. Nice job.
Click to expand...
No problem - I'm particularly busy for the next wee while, but I'll get something together and online and update this thread when it's done!
 
Hi Brian

I'd also be very interested in more details please, it looks great.

(I've been reading this forum for a while since deciding to get back into film photography, primarily 35mm, and your shutter tester finally made got me to register!)
 
No worries, with the speed my projects move at, and some house redecoration looming, I've plenty to keep myself occupied!
 
Flighter said:
No worries, with the speed my projects move at, and some house redecoration looming, I've plenty to keep myself occupied!
Click to expand...
Hi James, a bit OT (off topic), but welcome to tp and it's best corner, F&C!
 
Cuchulainn said:
I've been working on an Isolette that I picked up cheap off eBay. It's shutter was firing, but I wanted to test it with a bit more accuracy. I had a play today with the new Raspberry Pico. For those who like to play around with electronics, it's more like and Arduino than a Raspberry Pi - it's a small standalone computer that had a lot of inputs and outputs to connect to sensors, electronics, motors etc. It's also cheap - it costs about £4 and easy to programme in Python.

So, a few hours learning how to do some things, a phototransistor and a resistor later and I have a shutter tester that seems to work up to at least 4kHz. The picture and video below show it mounted in a board that includes a screen and some other nice things because I'm testing the Pico for work (and costs about £20, so still reasonably prices), but the whole tester could be built on breadboard and give the results back to a PC or laptop without needing this extra hardware. Oh, and the shutter seems close enough for a 60-something camera that I'm not going to open it up!
Click to expand...


It's great to see this, I missed it for a couple of weeks.
During lockdown, I spent some time learning/playing with Arduino kit (a small, cheap microcontroller). I did a few of the tutorials, then made a few of my own projects. It all works well.

Recently, I resurrected some of my old film cameras and have actually put film through a couple of my 50/60s rangefinders (yet to dev them). Along the way, I bought a couple of similar rangefinders that might not have good shutters. The shutter sound is different from those that I know work, but it's difficult to see they are wrong. So I too built a very simple shutter tester using a phototransistor and used the Arduino to time the "flash" as the shutter operates. It needs good light and gives convincing results at slow speeds. Although the spec of the phototransistor suggests that it should be fast enough, the apparent shutter speeds of all cameras tested begins to tail off as they get over 60th. It is dependent on getting good light onto the sensor, which is difficult when there's a lens in way.
I saw a video on someone's similar tester where he used a laser diode and a sensor. I've ordered a set, they're only a couple of pounds and it's fun to play with them.

Then, I realised that there is a problem in measuring the shutters of most of my rangefinders that use the "round the lens" shutters like the Prontor and the Compur. These are limited to around 1/300 to 1/500 sec. At the higher speeds, the leaves spend much of their time opening and shutting to the extent that at the fastest speeds, the shutter spends very little time wide open but are in transition for most of the operation. The finite shutter speed means that the shutter will not be open only for the nominal time on the dial, but will be open or part open for longer. It's the exposure that counts, not the time that the shutter is actually fully open.
So, when my shutter tester is put to work, the results will be a bit vague to give a good interpretation, I can only use them as a comparison with other cameras.
The traveling "slot" of curtain shutters should be as the dial is set, so there is use for the gadget.

Have you noticed this effect?
 
Hi Dave,

I have and I haven't! The times for the shutter were slightly long, so I reckoned this might have been the reason for it. I set the phototransistor up on a digital channel as a simple comparator, so it only tells me open or shut for light above a certain threshold. If you can get the laser aligned so that it's going through the edge of the lens at the shutter, then that would be a more reliable indication of fully open time. Alternatively, you'd need a light source that fills the full entrance aperture of the lens and then the ability to sample the voltage due to the photodiode/transistor so that you can plot the light coming through the lens at any given instance - it will plateau during the full opening time. I skipped that for two reasons: I didn't know how accurate the voltage sampling was on the pico in terms of timing, and I didn't want to have to mess around too much with large, bright light sources! I've done various other shutter testers in the past and, particularly with these old cameras, if I'm within 25% of the indicated shutter speed then I'm happy that the lattitude of negative film will let me get good exposures.
 
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