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  1. #21

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    Quote Originally Posted by Tom1956 View Post
    As upsetting as it is to accept, ... I've come up with equally dismal results. So I can [sort of] concur. Evidence the shutter is in bad need of CLA. And even then I doubt the speeds could come up to actual marked speeds and stay that way for more than a year. ... But I also believe his numbers are the sad truth.
    It is simply wishful thinking to expect older clockwork leaf shutters to give full speed; even newer ones are notoriously slow at higher marked speeds.

    That does not necessarily mean that they are inaccurate, however. Once you know that your 1/500 is really 1/160 or whatever, then just use that. If you really need reliable speeds faster than about 1/125, get a camera with a focal-plane shutter.

    FWIW I test my shutters by sound (ms between opening and closing peaks) and have very consistent results through the range of speeds. I use mostly smaller apertures, and thereby eliminate much of the opening-closing light loss. When I get my shutters CLAd, I always ask the tech to check the shutter speeds optically at f/22 and give me a list. This goes on the lensboard so I can use it in the field.

    Best,

    Doremus

  2. #22

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    The old Kodak Professional Dataguides used to have efficiency charts for leaf shutters used at different apertures and speeds.

  3. #23

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    I need an Avery label on the back of my focus hoods.

    f 16 22 32
    /125 x x -1/3
    /250 x -1/3 -2/3
    /400 -1/3 -2/3 -1

    from my RB67 hood & 90mm

    I think this means I need to reduce exposure by a stop at /400 f/32 i'd need to be using fast film though.

    For a TLR 11 16 22
    etc.

    without the Avery Id bracket.

  4. #24

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    The tester I build is great for focal plane shutter but with leaf shutter I think I need a redesign. I use a thru beam sensor that uses a very narrow beam of laser. It detect the shutter curtain edges very well and I see the signal on an oscilloscope. I would need a larger light source and sensor with an analog output to check the leaf shutter taken into account of the opening and closing.

  5. #25
    Bill Burk's Avatar
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    Quote Originally Posted by Tom1956 View Post
    ...I know Bill is disappointed at these numbers, because I've been there. But I also believe his numbers are the sad truth.
    Thanks Tom1956, I think you'll understand I'm not disappointed at all... I've got shutter speeds I can use.

    It's interesting how far the speeds are from nominal, which illustrates the often-heard expression: your light meter is probably the most accurate piece of equipment you have.

    It's also a good learning experience for me... Now I know how to verify shutters of any camera, and this will help me when it comes to interpreting other people's Zone System tests... Because the Zone System calibration is designed to incorporate shutter speed variations in the personal EI. I now understand some people may "correctly" arrive at an EI that is higher than rated speed.

  6. #26

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    Quote Originally Posted by Bill Burk View Post
    Thanks Tom1956, I think you'll understand I'm not disappointed at all... I've got shutter speeds I can use.

    It's interesting how far the speeds are from nominal, which illustrates the often-heard expression: your light meter is probably the most accurate piece of equipment you have.

    It's also a good learning experience for me... Now I know how to verify shutters of any camera, and this will help me when it comes to interpreting other people's Zone System tests... Because the Zone System calibration is designed to incorporate shutter speed variations in the personal EI. I now understand some people may "correctly" arrive at an EI that is higher than rated speed.
    And that's why on another forum about X-ray film and 8x10 cameras, I've seen guys claiming they're getting ASA 200 and 400 and other outlandish speeds out of X-ray film, when I'm lucky to be getting ASA 50. I've tested my shutter, and I don't think those guys have. I've seen 1/500 marked barely top out above 1/100. I know the truth.

  7. #27

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    Revisiting an old Betax No. 5 that I know has always suffered from speeds that are off. When using the record player set to 78 rpm and measuring the degrees of rotation, I calculated ~.0021 seconds per degree of rotation. Does that sound like an accurate figure?
    Entre La Espada y La Pared.

  8. #28
    RalphLambrecht's Avatar
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    how do you know that the 78 rpms are accurate?Do you havemains stabilization?
    Regards

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

  9. #29
    RalphLambrecht's Avatar
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    Quote Originally Posted by Bill Burk View Post
    Thanks Tom1956, I think you'll understand I'm not disappointed at all... I've got shutter speeds I can use.

    It's interesting how far the speeds are from nominal, which illustrates the often-heard expression: your light meter is probably the most accurate piece of equipment you have..
    sometimes precision is more important than accuracy
    Regards

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

  10. #30
    RalphLambrecht's Avatar
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    Quote Originally Posted by silveror0 View Post
    +1
    I assembled a sensor, based on Ralph's tester, and then made a jig out of MDB to hold both a lens-on-lensboard and a 75W flood in position, carefully aligning the sensor to the lens axis. Then used free download of the Audacity program to record the waveform on my PC screen. Then the program is able to measure the time from halfway up the rising wave (shutter opening) to halfway down the falling wave (shutter closing). All six of my large format lenses in leaf shutters checked out within tolerance, except for a couple of speeds, which I then labeled on the lensboard so I could make exposure corrections when using those speeds. I did, however, see a frequency of 120 Hz superimposed on the Audacity wave (which did not affect the ability of determine the shutter speed), but I was curious to learn the cause. So I contacted Chris Woodhouse (co-author of Way Beyond Monochrome 2nd Ed., WBM2) who is the electrical guru of this checker. His response to my query:

    "It is the mains - but you commonly get 2x the mains frequency (100Hz in the UK and 120 in the US). It normally comes from the fact that any power supply that has a bridge rectifier will cause current bumps 120 x per second."

    I've not tried my setup with a battery-driven light source yet to see if this oscillation goes away, because I'm satisfied with the results I got.
    Yes, Chris was thr electronic brain behind the shutter tester shown in WBM2nd Ed.it works wellwith audCITY AND I use it regulary.
    Regards

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

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