soundcard shutter tester works great!

[Mike Davis]

I should have said not just aperture-dependent, but also speed-dependent, because in principle the opening-closing action constitutes a larger portion of the overall exposure time as the speeds get faster. But just how fast the mechanical action is and where it starts to be an issue, I don't know.

Ah, ok.

I only averaged the speeds that I generally use. I did do some tests at 1/25th and 1/50 but I didn't save the results when I was testing. They seemed ok, but the peaks and valleys of the actual tests were small, again I guess due to the sensitivity of the photo-transistor and its placement in the camera.

Mike

[r.e.]

Previously I had tested the slow speeds by simply recording the sounds so I had an idea about the shutter.

Does this work significantly better than simply recording the sound?

[Marko]

All being said and as interesting as the project really is, we should keep in mind that this is a home-made device and thus have realistic expectations. I am going to use mine to determine if the shutter is in need of a CLA, not for real calibration.

[Mike Davis]

Does this work significantly better than simply recording the sound?

In my experience, it is more accurate and reproducible, so yes it is better.

Mike

[Mike Davis]

All being said and as interesting as the project really is, we should keep in mind that this is a home-made device and thus have realistic expectations. I am going to use mine to determine if the shutter is in need of a CLA, not for real calibration.

Yes, it is homemade, yes it is simple. But the theory and results are both logical and reproducible. That makes it valuable as a tool.

If I had a Calumet tester I would compare them. This has been done by others in the past and the results were very similar to the Calumet and more expensive testers.

I don't agree with the homemade must be lower quality school of thought. Sometimes the best things that we can use are those that we've made. I've found this to be true with a variety of items, from computers to knives, to gun parts, to shortwave radios, to lensboards, to electronics such as this. Simple things are often both more effective and higher quality than complex ones.

Mike

[Marko]

Yes, it is homemade, yes it is simple. But the theory and results are both logical and reproducible. That makes it valuable as a tool.

If I had a Calumet tester I would compare them. This has been done by others in the past and the results were very similar to the Calumet and more expensive testers.

I don't agree with the homemade must be lower quality school of thought. Sometimes the best things that we can use are those that we've made. I've found this to be true with a variety of items, from computers to knives, to gun parts, to shortwave radios, to lensboards, to electronics such as this. Simple things are often both more effective and higher quality than complex ones.

Mike

Oh, I agree with you, otherwise I wouldn't be doing diy projects to begin with

It's only that I prefer not to have high expectations of the things I make myself until I can verify their precision/reliability.

In this case, if my homemade shutter tester shows significant deviation, say a full f-stop for a Copal type shutter, I'll take it as an indicator that the time has come to send it for a professional CLA.

[Will Thompson]

does it works with apple computers ?

There is no reason it would not. Audio in is audio in.

It's having the software that makes it usable.

[cyrus]

There is no reason it would not. Audio in is audio in.

It's having the software that makes it usable.

The software that I use is Audacity which is free.
I would think the problem with the audio version is identifying the right sound of the shutter opening and closing?

[JW Dewdney]

this whole thing seems crazy complicated to do - in terms of circuit complexity. Why on earth wouldn't you just use a simple timer IC circuit and an opto-electronic sensor (photo-eye) - I'm POSITIVE there are TONS of instructions for doing that on the 'net.

[Will Thompson]

I would think the problem with the audio version is identifying the right sound of the shutter opening and closing?

Not sound per-say but a positive then negative edge of a square-wave. (open pop then the close pop)

You are using a light sensor not a microphone into an analog input similar to a digital storage scope.