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Winfried
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, January 16, 2004 - 02:44 pm: | 
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From time to time I check the shutter of a camera I just restored. This time it was the turn for a NKS shutter on a japanese MizuhoSix 6x6 folding camera. The shutter is basically an almost true copy of a Prontor II shutter, and these are easy to disassemble, so was this one, and there was no big problem to clean the blades etc. I don't know whether it was due to my mistreatment but the tiny hook which latches the cocking shaft broke off, so I had to disassemble the release levers and solder a new latch. (All this took MUCH longer than writing about it!)
Since this camera was designed for 6x4.5 format and has a 'fixed' mask (two hinged blinds) I am planning to use it for slide film and decided to verify the shutter speeds with a phototransistor assembly and a digital storage oscilloscope (Fluke ScopeMeter) to which I have access. It turned out that the slow speeds were quite exact but the high speeds were somewhat to slow - at 1/100 the actual speed just was 1/60 or so, and top speed /1/200 nominal) was around 1/100.
I rebent the cam of the cocking shaft which runs against the lever of the escapement gear to speed the shutter up a bit, and now the high speeds are much better although the highest speed (1/200 nominal) still rather is 1/150. When rebending that cam in most cases slow speeds are affected much more, and I had to refile the slow speed cams a bit. So this guy is running fine now at all speeds except for the top speed which is still a bit off and probably will remain that way.
More or less for fun I also checked the +70 years old Compur shutter on a 6x4.5 Ikonta. This guy was still running really strong! Most speeds were dead on, except for 1/50 and 1/100 which are approx. 10 p.c. too fast. This one did not reach the top speed (1/300 nom.), too, but the 1/250 it actually has comes pretty close. This shutter did not need any repair, just a few drops of lighter fluid on the speed escapement prior to the test.
However I have to say that on most cameras where I cleaned (and sometimes repaired) the shutters I did NOT test the shutter speeds and there was hardly any camera where the first roll of slide film did not turn out satisfactorily. |
JIM
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, January 16, 2004 - 06:03 pm: |
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Winfried-
I feel your pain. I often think about shutter testers and that I should build or buy one. On the other hand, maybe ignorance is best. The real test is still what the film looks like. Lots of latitude in black&white.
Regards,
JIM |
charlie stobbs
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, January 17, 2004 - 07:38 am: |
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I don't know what speed CD drives turn at but a 33 1/3 RPM turntable with an index mark on the base and a record with suitable marks painted on is a lower tech method of testing shutter speeds. |
Henry
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, January 17, 2004 - 04:29 pm: |
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If you think shutter speeds on a lot of old shutters are screwy, try testing the apertures! Testing them is real simple. I show my first one in the test equipment section. Basically a digital multimeter and the CdS cell out of a junker Canonet.
Now...try combining the two! Apertures and shutter speeds...EV tester. There is a tester for that too. Albeit much more difficult to make. If built and calibrated well it'll give the same results as film testing only with immediate results and no added expense.
Henry |
rick oleson
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, January 17, 2004 - 10:23 pm: |
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High speeds are off on leaf shutters, almost by definition: Since the shutter blades open from the center out, and at the highest speed they are in constant motion, the center of the lens gets a much longer exposure than the edges. Ideally, the shutter should be timed to give the light-transmittance equivalent of the marked speed, but even this is impossible as it will be different at different apertures. A shutter passing 1/500 second worth of light at f/3.5 will be passing about 1/250 second at f/16, and may read as 1/250 on a shutter tester at either setting (depending as much on the design of the tester as on the accuracy of the shutter).
I don't even bother testing high leaf shutter speeds on a tester; the only reliable test is a roll of film.
 = |
Winfried
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 18, 2004 - 02:38 am: |
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Rick, you are quite right. I just put a phototransistor behind the shutter, and of course this does not sense the whole 'stream of light' passing through the shutter. It would be more accurate to put the sensor in the film plane (focus point).
According to international standards, shutter speeds are measured between the 50p.c. points of the rising and the falling edge of the light stream. Of course the 'fully open time' of a shutter set to 1/300 is quite shorter than the time measured to this standard. I found that most leaf shutters have rise and fall times around 1...2 milli-seconds which may cause a significant error when set to 1/300 where nominal open time is 3.3 milli-seconds. |
Mark Sarafyan
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, April 29, 2004 - 07:23 pm: |
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I am a collector with about 120 cameras, ancient and modern. I would like to test their shutters before I put them on sale. Where can I buy a simple and reliable shutter-speed testing device for both between-the-lens and focal-plane shutters? I am not looking for a high-precision device. Calumet used to stock one but not any more. Please help me. |
David Hansen
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, July 23, 2004 - 08:08 am: |
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Hi Mark, Micro-Tools has what looks like a real nice one and I intend to buy one... cat. price is about $225 Dave |
Slow Hands
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, August 24, 2005 - 10:02 pm: |
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The Calumet Tester is available online for $110 plus shipping:
https://www.calumetphoto.com/ctl?ac.ui.pn=cat.CatTreeSearch&PAGE=Controller&keywords=shutter+tester&x=24&y=12 |
