Shutter tester - the DIY way

[Denis Pleic]

I was quite stumped when I read here on LFF that old Calumet shutter testers are sold for $200-$300.

Given the way the economy is going, perhaps a DIY way would be acceptable for some of you.

So, I've put up a Web page describing a new and improved version of the sound card shutter tester that a friend of mine has made after I've shown him my old version.

The new one is improved: does not need batteries, has its own light source, and provides more precise measurements. I've also prepared a small Excel file with some formulas, where you can enter the measured duration of the "sound", and the actual speed is shown, together with the deviation from the marked speed (in %).

The gadget looks rather ugly, but does its job. Given that the alternative costs at least $200, this one could be interesting :)

You need a computer with sound card and a microphone input, sound recording software ("Audacity" is freeware), and that's all.

The page explains it all.

The link: here (http://www.hrtranslations.com/photo/shutter_v2/shutter2.html).

Denis

[willwilson]

I wonder if an actual microphone might work just as well. Shutters tend to have a fairly distinct open and close sound.

[ic-racer]

I wonder if an actual microphone might work just as well. Shutters tend to have a fairly distinct open and close sound.

I just hooked a cardioid mic up and tried this a while back. It takes some clever interpretation of the sound waveform to figure out when the blades actually open and when they are all the way closed. Works better with the longer times. I did try placing a white noise source behind the shutter but even then the frequency was not high enough. The first waveform peak after shutter opening did not necessarily correspond to the exact point of opening. A very high frequency source would be needed for accuracy of the high speeds. Next time I do it I'll just hook up the little gizmo that is described in the above web pages.

[willwilson]

Frequency of sound is not an issue. You would be looking for amplitude peaks. Once when the shutter opens and once when it closes. White noise is equal parts of all frequencies of sound, usually limited by the playback device. A higher quality small diaphragm condenser microphone would probably work best, as it would have a slightly faster and more accurate response time than a dynamic. Polar pattern also would not matter really.

[Ivan J. Eberle]

Why fool around with a microphone and interpreting the opening and close times in sound, when you can super-accurately time the actual light for the cost of a photo-transistor?
Even having bought the very best photo-detector I could find with a latency of a microsecond or so, I still built my a sound-card shutter tester for about $20 in materials. Took all of about an hour to put together, including waiting for the soldering iron to warm up.

p.s. while the link above points to a page with broken links to the embedded images, five minutes of Googling around should turn up several very basic designs and how-tos.

Mine is just the phototransistor inline with a 1.5V AA cell in a holder, with the output routed through 3.5mm jack, enclosed in a small project box with the phototransistor mounted flush and epoxied into a hole in the center of one flat side.

[Glenn Thoreson]

Wow! 200 to 300 bucks for that little Calumet? I'm glad I bought mine new when they were 80 bucks. What made them so valuable all of a sudden?

[Jim Graves]

I have used two of the photo-transistor home brew models (one I built and one off ebay) ... tested them on two professionally timed shutters that I had just gotten back from a commercial photo service shop.

The photo-transistor models were fairly accurate up to about 1/50th of a second. After that, they got further and further off ... don't know if it's the reaction time in the photo-transistor, the circuit, or what.

When the guy I bought the original from introduced a newer model with a faster photo-transistor I wrote, told him I was thinking of purchasing the newer version, and asked him if it was more accurate at the higher shutter speeds. He told me to "save my money."

I still use them for my old folders and packard shutters, but little else.

[Anupam]

A few months ago, I described a way to test shutters with a DSLR (http://decisivemomentum.blogspot.com/2008/07/using-dslr-as-shutter-tester.html). If you already own one, it's a very cheap and reasonably accurate method to try.

I have tried the photo-transistor testers and I agree that they go a bit wobbly at higher speeds.

[Ivan J. Eberle]

Mine seems extremely precise and consistent, used with Audacity (at the highest recording resolution) and a MacBook Pro 15" Duo Core 2 laptop.

My 3 large format lenses are all within 1/8 stop of the indicated speed, until about 1/125 and then two of them start to slow down. (One could anticipate that with a 60 year old Rapax shutter, more surprised with a ten year old Copal). They're consistent, at least. Happier to have spent a few hours analyzing all this without burning film and chemistry (not to mention burning more gasoline to reshoot).

[Struan Gray]

The photo-transistor models were fairly accurate up to about 1/50th of a second. After that, they got further and further off ... don't know if it's the reaction time in the photo-transistor, the circuit, or what.

Sound cards are not meant to measure DC. In a setup like this how they cope with high shutter speeds is complicated by the (unknown) DC rejection circuit on the sound card's input.

Using a light source that flashes at 15 kHz like Denis' setup gets round the problem to a large extent: there is still an unpredictable DC drift, but the 15 kHz oscillation comes through loud and clear.

Phototransisters do have relatively slow reaction times, especially cheap ones, but most are more than fast enough to time a LF shutter.

[Denis Pleic]

p.s. while the link above points to a page with broken links to the embedded images, five minutes of Googling around should turn up several very basic designs and how-tos.


Ivan,

Do you mean that you can't see the photos on my Web page - i.e. the link I provided in the original post?

If so, please, let me know, and I'll try to fix it...

BTW, do the others see the page properly (with images and everything)?

Denis

[cowanw]

I can see everything; very complete.
good work
Regards
Bill

[ic-racer]

Frequency of sound is not an issue. You would be looking for amplitude peaks.


As I pointed out, the frequency of the sound source placed behind the shutter is the limiting factor in the resolution of the system. For example, the waveform peak of a low frequency sound (placed behind the shutter) will not even show up at a fast shutter speed. A very high frequency sound would be needed to have the resolution to pick up where the blades open. For example as the blades open (which may take as little as 1/2000 of a second) you would like to have a 5 or 6 waveform peaks to plot out the opening phase. That would require a sound source placed behind the shutter with a frequency of about 10,000 cps.

[Gordon Moat]

I just use a microphone and audio software. Then I can look at the audio waveform, and measure the timing directly. Many laptops have microphones built in, and if your audio software recognizes the built-in mic, then you are all set.

Ciao!

Gordon Moat Photography (http://www.gordonmoat.com)

[Paul Kierstead]

As a matter of curiosity, does anyone know how leaf shutters compensate for leaf travel at higher speeds? Focal plane shutters typically use a "travelling slit" to ensure all the film plane gets the same exposure. It would seem to me that at higher speeds a leaf shutter would over expose the center (or under expose the edges), further adding to the "fall off" effect. Does measuring speed at the edge give a different result then the middle?

[Struan Gray]

Leaf shutters don't compensate for the leaf travel time. They don't over-expose the centre because they lie in the middle of the lens near the aperture.

The leaf travel time does have consequences though. The most often encountered on in LF is that at the highest speeds the effective exposure time is longer at small aperture stops. At the top speed the leaves just get to the edge of the wide-open aperture in time to turn around and close again. With a small aperture the leaves clear the centre hole much faster, and the effective exposure is longer.

The second consequence is seen when you take photos at the fastest shutter speeds and wide apertures with out-of-focus bright highlights. As is exhaustively documented in the various bokeh threads, the highlights take on the shape of the aperture. The subtle point is that the shutter changes the aperture shape with time, and at the fastest speeds the aperture is never 'normal'. The result is shown in the attached photo: background highlights turn into little flowers. In this case, the shutter does overexpose the centre, and the star-shape you get as the shutter leaves start to open.