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  1. #31
    Bill Burk's Avatar
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    Quote Originally Posted by RalphLambrecht View Post
    how do you know that the 78 rpms are accurate?Do you have mains stabilization?
    As I understand, the 60-cycle frequency of our mains in the states are guaranteed to a very high level of precision... A friend of mine works at a power company and told me how the breakers kick out any circuit that deviates even slightly in frequency. It's the voltage that fluctuates freely around 120 nominal and I wouldn't be surprised if it varies 5 volts.

    The old record player I used in the test has a synchronous motor, and its speed is governed by the mains. Now I know not to trust an old record player speed to be engineered at "exactly" 78 RPM. And it's not. I calibrated it (the old one runs at 79.2 RPM) to a German-engineered Dual CS-5000.

    That particular turntable has a unique design. It's belt-driven with a computer controlled speed regulator. A small bar on the platter passes between a light source and a photo-detector on the base. Once per revolution the turntable speed is checked by a quartz-controlled clock. Any deviation from the selected speed and the needle lifts.

    p.s. Shots from the camera are pleasingly well exposed, since I calibrated the shutter speeds. It is rewarding to get properly exposed negatives from a vintage camera. Now I see a need for hand-holding skills and scale focus skills, because many of the shots suffer camera shake and focus mistakes. But that's something I can work on.

    I'll recommend performing this procedure (calibrating vintage shutter speeds) on particularly robust cameras and lens/shutters. For example, this is where you can appreciate the value of a high quality-build camera, because you can trust that tests like this remain valid for long enough to be worth the investment in time.

  2. #32

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    Quote Originally Posted by Bill Burk View Post
    As I understand, the 60-cycle frequency of our mains in the states are guaranteed to a very high level of precision... A friend of mine works at a power company and told me how the breakers kick out any circuit that deviates even slightly in frequency. It's the voltage that fluctuates freely around 120 nominal and I wouldn't be surprised if it varies 5 volts.

    The old record player I used in the test has a synchronous motor, and its speed is governed by the mains. Now I know not to trust an old record player speed to be engineered at "exactly" 78 RPM. And it's not. I calibrated it (the old one runs at 79.2 RPM) to a German-engineered Dual CS-5000.

    That particular turntable has a unique design. It's belt-driven with a computer controlled speed regulator. A small bar on the platter passes between a light source and a photo-detector on the base. Once per revolution the turntable speed is checked by a quartz-controlled clock. Any deviation from the selected speed and the needle lifts.

    p.s. Shots from the camera are pleasingly well exposed, since I calibrated the shutter speeds. It is rewarding to get properly exposed negatives from a vintage camera. Now I see a need for hand-holding skills and scale focus skills, because many of the shots suffer camera shake and focus mistakes. But that's something I can work on.

    I'll recommend performing this procedure (calibrating vintage shutter speeds) on particularly robust cameras and lens/shutters. For example, this is where you can appreciate the value of a high quality-build camera, because you can trust that tests like this remain valid for long enough to be worth the investment in time.
    Logically, it's the most sure and foolproof way. Burns up a little film, but still the truest way. Proof positive the camera does not lie; to quote an old expression (I think Barney Fife said that).

  3. #33
    Bill Burk's Avatar
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    Quote Originally Posted by RalphLambrecht View Post
    how do you know that the 78 rpms are accurate?Do you havemains stabilization?
    Ralph,

    Do you have any idea how hard I was laughing while answering your question? The best humor has a kernel of truth in it.

    I couldn't have made up a funnier answer than saying I calibrated to German engineering... and it's really what I did.

  4. #34
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    German engineering is no onger what it was cracked up to be.what you need is German engineering with Jspanese quality controland ,I do know a good deal about both.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  5. #35
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    Seeing you have many suggestions I decided to add another one to the mix. I rigged a simple one for my DIY cine cameras, simply a photodiode hooked up via a minijack to a sound card (or mic jack on Mac) and used Soundboth although audacity can work too. Lightsource -> Shutter -> Photodiode connected to PC.
    "The real work was thinking, just thinking." - Charles Chaplin

  6. #36

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    Quote Originally Posted by RalphLambrecht View Post
    German engineering is no onger what it was cracked up to be.what you need is German engineering with Jspanese quality controland ,I do know a good deal about both.
    I think the engineering is still good, but the manufacturing, for one reason or another, is not what it used to be.

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