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Monday, November 10, 2014

rehab

I've been hobbling around for the past week with a bit of a hip strain from chasing the Marigold Parade last weekend.  Seemed a good excuse to hang out at home and work on a project that didn't require any significant level of mobility.  I borrowed a home-built shutter tester from a friend and applied it to measuring the performance of a number of my old cameras.

Shutter tester and Kodak Retina IIc

There is a light-sensitive phototransistor out on the end of the boom which is maneuvered in close to the rear lens.  A flashlight is shone on the front of the lens and the shutter is tripped.  The result is captured through a connection to the microphone port by the freeware Audacity sound recording/editing program.

Audacity Sound Recording and Editing Program, Retina II results

The dark block encloses the opening and closing points of the shutter on my Retina II and the length block at the bottom center shows the duration of the exposure to be 0.012 seconds.  Divide 1 by that amount and you get a shutter speed of 1/83 with the shutter having been set to 1/100.  When I set the Compur-Rapid shutter to 1/250 I got a recorded speed of 1/200.  That is better performance than I get from my Retina IIa, and I was surprised and pleased because the Xenon lens on the II model is probably the best on any of my Retinas.

I tried out the tester on quite a few of my cameras.  The Compur shutters produced very smooth wave forms and the results repeated consistently.  The box camera results all showed speeds in the expected 1/30-1/40 range, but the wave forms were noisy and I didn't have a lot of confidence in the absolute numbers.  Still, the comparisons are interesting, and the relative values are useful.  I didn't try speeds above 1/250 as it seemed that would be stretching the device's capabilities beyond its potential accuracy.

Mid-way through my shutter testing, this mantis showed up on my front porch, so I snapped a few portraits with the digital:




4 comments:

Jim said...

What a cool setup to test shutter speeds. Very clever.

Do you plan to adjust any of your cameras to make their shutters more true to speed?

Mike said...

I may tune up one or two of my favorites. In general, though, if they are only off by half a stop I don't think it is worth much concern. It is nice to know the actual speeds, however, so as not to attribute problems to the wrong issue.

One thing I have found out is that some of my assumptions about the shutters on my simple box cameras are wrong. They are actually all pretty close in shutter speed. It seems that the real issue is the smoothness of the shutter release and other ergonomic differences that are more likely the source of differences in performance.

One thing that did surprise me completely was the speed on my little p&s Vivitar Ultra Wide and Slim cameras. One is shooting at about 1/75 and the other about 1/90. I had previously bought the oft repeated claim that they were at 1/125. In practice, that is a pretty small difference given the latitude of modern films, but it is good to know anyway.

Julio F said...

Shutter speeds should be within about 20% of nominal. The mechanical setup of the tester is very practical.

I have done the same, but with much less class, just holding the sensor with tape in the film gate.

Thanks for the data on the Vivitar USW, I had never seen it tested before. It looks like a nominal 1/100.

Mike said...

I recently acquired a simple tester from a Romanian guy on ebay that requires no battery. Results are comparable to the battery-driven one I was using. I'll have more to say on the subject sometime soon.