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  1. #11

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    I echo that, shutterfinger--thanks. Had seen your handle on occasion, but never connected it with a good knowledge on shutters. Regards.

  2. #12

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    Quote Originally Posted by Hatchetman View Post
    I recently had a Supermatic 800 shutter CLA'd by Paul Ebel. It was his opinion that the fast shutter speeds never did, in fact, reach those speeds. Now the shutter is accurate to 1/100. Then 1/200 is also 1/100. 1/400 is actually 1/200 and 1/800 is actually 1/400, which is pretty good. I just need to remember that when using.
    Would that be the Synchro-Rapid 800 you are talking about? I happen to have one too, in a Kodak Tourist. For a long time I had resisted buying the top-end Tourist I wanted (the one with the Anastar lens), just because of all the stories about how unreliable and potentially difficult to service that 800 shutter was. But I finally decided to risk it, partly because of the cool factor of the double-ended shutter mechanism (I guess I'm a bit of a gadget freak), and because I really just wanted to see how that Anastar lens would perform. It turns out the 800 on the one I bought is in fact going to need some service - surprise, surprise - so we'll see how it goes! In the end if I could get to the clean sequence you mentioned, topping out at 1/400 I would be happy. It is sounding more and more like that is the best I can hope for with the Flash Supermatic too (topping out instead at 1/200). As long as the speeds are consistent I think I could probably live with that.

  3. #13
    shutterfinger's Avatar
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    Had seen your handle on occasion, but never connected it with a good knowledge on shutters
    I'm just a good electronic and mechanical technician that picked up a few service manuals and taught myself the shutters. I serviced about a dozen Supermatics, about the same number of Graphex/Rapax, and some Compurs, Ilex, and a few Betax.

    I think too importance is placed on a shutter speed tester reading. I have been working out testing on Graflex SLR shutters. I did some work on making a shutter speed tester and posted my findings on both photo.net ( http://photo.net/large-format-photog...044cW?start=10 ) and Graflex.org ( http://www.graflex.org/helpboard/viewtopic.php?t=6105 ). I recently had an Anniversary Speed Graphic in 4x5 format that I CLAed and it tested that the 1000 speed was around 1/550 to 1/600. I metered an exposed some fresh white calla lilies at 1000, 500, 250, and 125 varying only the aperture. The result was the density on film suggested the variance in density to be .5 stop or less across the exposures.
    The film used in my test was Arista EDU UIltra ISO 400 developed in HC 110. The flowers were in bright sun with deep shades.

    Take a shutter speed tester readings with a grain of salt until some carefully executed test exposures are made to verify or refute the speed tester results.


    Springs weaken with age and use. Shafts, pivot pins, and bushings wear faster with dirt and dried lubrication. Wear results in play which prevents parts from moving freely.
    Last edited by shutterfinger; 06-12-2014 at 01:40 AM. Click to view previous post history.

  4. #14

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    That's about the way I see it on springs and parts wear, Shutterfinger. I'm not big on actual film exposure tests as my defining standard, as there's enough variable there to mislead the results. Still think lab testing for speeds is best. Problem is ,cutting up computer mice for the IR sensors and sound-card audio programs are not exactly Apollo 11 grade tests. Luckily I now know that a 1947 shutter was a worn out piece of junk in 1948 after the first 4 rolls of film.

  5. #15
    Hatchetman's Avatar
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    Quote Originally Posted by Denverdad View Post
    Would that be the Synchro-Rapid 800 you are talking about?
    Yes. In the Tourist. Pretty cool camera.

  6. #16

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    In spite of(in some opinions) being instantly worn out or only being good for
    four rolls of film, these things served a great many people for a good long time.

    Most leaf shutters typically do overexpose at their highest speeds.
    This is caused by the the film getting additional exposure as the blades
    open and close.

    You can see why if you open and close the blades slowly/manually.
    In any case your camera is perfectly good to use as long as you know
    the error involved.
    Heavily sedated for your protection.

  7. #17
    Ken Nadvornick's Avatar
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    Quote Originally Posted by John Koehrer View Post
    Most leaf shutters typically do overexpose at their highest speeds.
    This is caused by the the film getting additional exposure as the blades
    open and close.
    This was always my common sense understanding as well. Simplified, if it takes the blades a millisecond to open, and another millisecond to close, that extra transitional "open" time gets added to the nominal shutter speed time.

    If the shutter is set for a correctly calibrated 1/500 sec once it reaches full open, then the addition of that 2/1000 sec effectively doubles the expected exposure time to 1/250 sec.

    My low-mileage and recently serviced Graphex on my Crown measures: 1/400=1/200, 1/200=1/150, 1/100=1/100, with all the rest near perfect down to 1 sec.

    At 1/200 sec I know I can handhold the beast for critically sharp negatives, which is the only true non-negotiable shutter requirement for this camera. And as long as I know the shutter speed deltas, I can simply compensate for them when reading my light meter.

    My base sunny-16 setting for Ilford HP5+ thus becomes 1/400=1/200 sec at f/22.

    Ken
    "They are the proof that something was there and no longer is. Like a stain. And the stillness of them is boggling. You can turn away but when you come back they’ll still be there looking at you."

    —Diane Arbus, March 15, 1971, in response to a request for a brief statement about photographs

  8. #18
    shutterfinger's Avatar
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    My limited testing showed it takes the shutter blades .1 ms to .3 ms to open and faster close times once the delay mechanism has released the blade controller and the cocking spring returns the blade controller to the closed position.
    One must factor in the rise and fall times of the sensor/electronics, the sensor's angle of view, and the fact that a leaf shutter is basically a variable aperture and as the shutter opens and closes there is a small portion of that open time that the shutter opening is 3 stops and more smaller than the exposure aperture resulting negligible exposure if any exposure density build up on the film.

  9. #19
    Ken Nadvornick's Avatar
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    Agree with all of those geometry-enforced considerations.

    My understanding is that factory calibration means a shutter being open all the way for the nominally marked time. Transition time does not factor in to nominal time. So the shorter the nominal, the higher the percentage is the (fixed) transition of the total aggregate open time.

    And since no mechanical shutter can ever open truly instantaneously, then no shutter can ever match the nominally marked times. However, only with the shorter times does the transition time become a large enough percentage of the total time to matter.

    My assumption has always been that this is the reason behind marking the highest nominal leaf speed as 1/400 instead of 1/500, as the arithmetic progression would require. Just as a recognition of the practical geometric design limitations.

    So I guess what I was really trying to say was that none of this really matters in practical use.

    If one's top-end shutter speeds are off by a stop slow, just compensate for it. And as long as I can handhold a 4x5 camera without blurring the negative, I'm good. And the shutter is doing its job just fine.



    Ken
    "They are the proof that something was there and no longer is. Like a stain. And the stillness of them is boggling. You can turn away but when you come back they’ll still be there looking at you."

    —Diane Arbus, March 15, 1971, in response to a request for a brief statement about photographs

  10. #20
    Ken Nadvornick's Avatar
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    Quote Originally Posted by shutterfinger View Post
    My limited testing showed it takes the shutter blades .1 ms to .3 ms to open and faster close times...
    Was that a typo? The blades actually opened in a measured 1/10,000 sec?

    Ken
    "They are the proof that something was there and no longer is. Like a stain. And the stillness of them is boggling. You can turn away but when you come back they’ll still be there looking at you."

    —Diane Arbus, March 15, 1971, in response to a request for a brief statement about photographs

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