Spyderman
Well-known
I've always wanted to build have a shutter tester. I remember our teacher at university in lab telling us "if you don't measure, you don't know!" Knowing the precise shutter speed of my pretty old cameras (some 20 to 30 years old) would be nice, so I build one. (a few different schematics are available on the web) It's just 2 phototransistors, powered by USB and output recorded by PC sound card mic input.
When shutter was built I proceeded to testing.
My SLR system is some Oly OM cameras and I've got 2 RFs: Leica M6 and Bessa R2.
My oldest are a pair of OM-1n. One brassed that has undergone a difficult surgery, one like new. On both the fastest 1/1000s was more like 1/450s
Ouch. On the pristine sample the difference between left and right edge of frame was 53% (more than 1EV!) Thanks to the repair manuals at olympus.dementix.org an easy fix. Tuned the shutter curtain tension and now both bodies are within 10% of specs except for 1/1000 which is now more like 1/600. I didn't want to overtension it.
Next in age is an OM-4. Brassed, worn, dented, with bent flash shoe and peeling covering. Got in trade with Pitxu (R.Jenkinson) a few years back. 1/2000 measured actually 1/900, and 57% (again more than 1EV) difference in illumination of R and L edges of film gate :bang:. Some 3 hours of repeated tuning and measuring later 1/2000 is actually 1/1700, 1/1000 is actually 1/900 and difference in illumination below 20% at fast speeds and below 5% at 1/500 and slower. I was very surprised that the electronic shutter of the about 25 years old camera is this precise (I mean very very good).
My Leica M6 was made sometime in 1993. Measured speeds all over the place: 1/1000 actually 1/350 ! 1.7EV slower After some 4 hours of tuning and with help of this article (http://feuerbacher.net/photo/repair/LeicaMP/LeicaMP.html) I managed to get 1/1000 to 1/600, but it was more pain than any of the Olympus OMs. Adjusting tension of shutter curtains wasn't enough and I had to mess with the "slit width adjustment". Unfortunately the slit-width makes it very difficult, as with a narrower slit, the difference in illumination of R and L sides is more pronounced. Moreover the movement of the slit adjustment excentric screw are very subtle (hardly any movement at all).
The newest is the Bessa R2. I expected it to be the most precise. I was quite disappointed to find that all shutter speeds were 10 to 25% slower (0.5 EV) and the difference between top and bottom parts of frame up to 35% (0.7 EV). Not that great. And not easy (I'm not sure if it's even possible) to fix
Overall the shutter tester is very handy to have. But to be honest, I must say that I never noticed the overexposure or difference in illumination on L/R sides of frame. Negative film has so much latitude, that error up to 1 EV seems negligible. But when using slide film, it's good to know which body to choose based on the precision of shutter.
When shutter was built I proceeded to testing.
My SLR system is some Oly OM cameras and I've got 2 RFs: Leica M6 and Bessa R2.
My oldest are a pair of OM-1n. One brassed that has undergone a difficult surgery, one like new. On both the fastest 1/1000s was more like 1/450s
Ouch. On the pristine sample the difference between left and right edge of frame was 53% (more than 1EV!) Thanks to the repair manuals at olympus.dementix.org an easy fix. Tuned the shutter curtain tension and now both bodies are within 10% of specs except for 1/1000 which is now more like 1/600. I didn't want to overtension it. Next in age is an OM-4. Brassed, worn, dented, with bent flash shoe and peeling covering. Got in trade with Pitxu (R.Jenkinson) a few years back. 1/2000 measured actually 1/900, and 57% (again more than 1EV) difference in illumination of R and L edges of film gate :bang:. Some 3 hours of repeated tuning and measuring later 1/2000 is actually 1/1700, 1/1000 is actually 1/900 and difference in illumination below 20% at fast speeds and below 5% at 1/500 and slower. I was very surprised that the electronic shutter of the about 25 years old camera is this precise (I mean very very good).
My Leica M6 was made sometime in 1993. Measured speeds all over the place: 1/1000 actually 1/350 ! 1.7EV slower
After some 4 hours of tuning and with help of this article (http://feuerbacher.net/photo/repair/LeicaMP/LeicaMP.html) I managed to get 1/1000 to 1/600, but it was more pain than any of the Olympus OMs. Adjusting tension of shutter curtains wasn't enough and I had to mess with the "slit width adjustment". Unfortunately the slit-width makes it very difficult, as with a narrower slit, the difference in illumination of R and L sides is more pronounced. Moreover the movement of the slit adjustment excentric screw are very subtle (hardly any movement at all).The newest is the Bessa R2. I expected it to be the most precise. I was quite disappointed to find that all shutter speeds were 10 to 25% slower (0.5 EV) and the difference between top and bottom parts of frame up to 35% (0.7 EV). Not that great. And not easy (I'm not sure if it's even possible) to fix
Overall the shutter tester is very handy to have. But to be honest, I must say that I never noticed the overexposure or difference in illumination on L/R sides of frame. Negative film has so much latitude, that error up to 1 EV seems negligible. But when using slide film, it's good to know which body to choose based on the precision of shutter.
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nobbylon
Veteran
Reading errors can be huge with these home testers. I built 4 myself and they all read differently. It seems to depend on the positioning of the photo diode, type of diode and illumination used.
I still use an old crt as a good yardstick for the high speeds. FWIW I would never mess with the slit width, only the curtain tension and even then gently!
I still use an old crt as a good yardstick for the high speeds. FWIW I would never mess with the slit width, only the curtain tension and even then gently!
Spyderman
Well-known
Well, the tester I made uses 2 phototransistors positioned 32mm apart to be able to measure exposure time on both edges of frame.
BTW sampling rate of the sound card (44kHz) is enough to be able to measure the time with precision to 1/44000s. I record the signal using Audacity (free sound editor software) and then zooooom in and measure the time between peaks.
Probably too much information in the first post. I wanted to share my experience with this, and it might be a bit difficult to read.
The point is that the shutters were waaay off, and still I haven't noticed it in my pictures. And that after I tuned the shutters, I'll be slightly more confident with slides that any exposure error is only my own fault
BTW sampling rate of the sound card (44kHz) is enough to be able to measure the time with precision to 1/44000s. I record the signal using Audacity (free sound editor software) and then zooooom in and measure the time between peaks.
Probably too much information in the first post. I wanted to share my experience with this, and it might be a bit difficult to read.
The point is that the shutters were waaay off, and still I haven't noticed it in my pictures. And that after I tuned the shutters, I'll be slightly more confident with slides that any exposure error is only my own fault
UberSquid
Member
having access to a recording studio I took several cameras in after hours the other day to see if I could capture the sound profile of the shutter opening and closing. With the editing software we use I was able to zoom in on the waveform and measure shutter open time. It was repeatable and didn't vary more than a ms or two from test to test. I really believe that if you know what your doing a good quality microphone is just as good if not better than any of the homemade systems I've seen.