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  1. #21
    michaelbsc's Avatar
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    Quote Originally Posted by jnanian View Post
    i would guess the typically the "I" setting
    on a fixed shutter speed camera
    from that period was around 1/100S
    a roll of film is cheep, you could alway shoot 2 rolls
    - one with that camera, and one with another, process them at the same time
    and compare the negative density to determine the shutter speed.
    i have a few cameras that say "I" and i rate the shutter at about 1/100...
    even if it is off a little bit, it doesn't really matter too much

    nice camera!
    have fun

    john


    with
    I'm not so sure that something that old would have been 1/100 for the instantaneous setting. Clearly this is "just a guess" on my part, but I'd bet it was closer to 1/20 or 1/25 for the film speeds of the day, particularly if it has a fixed f/12.5 aperture.

    Of course that doesn't mean a thing about what it currently fires. However it can't be a complicated mechanism, so getting it back in proper order should be possible, especially if it works now. Clearly all the parts are there an not broken if it fires.

    MB

  2. #22
    bobwysiwyg's Avatar
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    Quote Originally Posted by srs5694 View Post
    The TV test that sun of sand mentions can be done without film; just open the back and look through the film gate as you shoot a TV. This Web page describes the process in more detail. Note that this technique works only with older raster-scan TVs and computer monitors, and you must be aware of the TV/monitor's refresh rate. (This can be just about anything for a computer monitor.) If you've got a new high-def LCD, plasma, etc. TV or computer monitor, this technique won't work. It's a bit of a seat-of-your-pants approach, since you can't get an exact number from it, just a guesstimate of "oh, that looks about right for 1/125s" (or whatever). FWIW, I used this technique to adjust the shutter speed on my Kiev 6C, which arrived with shutter speeds that were very badly off. I'm sure my Kiev's shutter speeds are still off, but not badly enough to cause me serious problems.

    I've seen plans on the Internet for an elaboration of the sound card technique described by ntenny: [url=http://www.davidrichert.com/sound_card_shutter_tester.htm]one,[url] two, three. The idea is to hook up a phototransistor to a computer's sound card, position that phototransistor behind the film gate, shine a light through the lens or lens mount, use an audio recording program to record the output from the phototransistor as you fire the shutter, and measure the time the shutter was open using the audio program. Parts are supposed to cost about $5. There's a guy who sells these on eBay for $51 (shipped) if you're completely hopeless with electronics. I'm planning to put one of these together myself soon (maybe this weekend, in fact), but I've not gotten around to it yet.
    This seemed like the logical thread for more of my newbie questions. I'm new to 4x5, I've exposed perhaps 20 sheets. Note I didn't say I've taken 20 photographs. I have three lenses; 135mm, 150mm and a 210mm, all used from eBay. I've wondered just how accurate they are. I finally got around to acquiring the gadget described above. Pretty interesting gadget and I've used it to check all three lenses. Now that I have, it raises several questions for this newcomer.

    I've seen references to CLA, which I'm assuming stands for Clean/Lub./Adjust? How accurate, in terms of absolutes are shutter times after a CLA? Is there some sort of allowable +/- deviation and the shutter is still considered OK?

    I compared each shutter, at each speed and now have values for deviation from the absolute. My next question is, if one were to compute the % difference from the absolute, correct value for a given shutter speed, could this be used to translate into an f-stop difference? That is, say a given speed were off by 25%, would that correlate into a 1/4 stop difference?
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  3. #23
    ic-racer's Avatar
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    Quote Originally Posted by bobwysiwyg View Post
    I compared each shutter, at each speed and now have values for deviation from the absolute. My next question is, if one were to compute the % difference from the absolute, correct value for a given shutter speed, could this be used to translate into an f-stop difference? That is, say a given speed were off by 25%, would that correlate into a 1/4 stop difference?
    Close enough for practical purposes.

    To be exact, use the log scale. On the log scale the 1/4 point between 1/30th and 1/60th is 1/35.6th. If you just figure 25% then the (close but technically incorrect) answer is 1/37.5th.

  4. #24
    bobwysiwyg's Avatar
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    Close enough for practical purposes.
    I'll go with that, thanks. I would have thought I was unlikely to be able to detect anything below a half stop visually (that is by the negative or the print) but is seems I can. I took notes on my shots and one negative in particular seemed "thinner" than I would have expected or liked. Turns out I could trace it back to a lens and shutter speed that turns out to be off by 30% so maybe there's hope for me yet.

    I thought keeping a record of the shutter speeds might help identify future changes or declines in performance.

    Any sense for what the level of accuracy, +/-, one might expect after a professional servicing?
    WYSIWYG - At least that's my goal.

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  5. #25
    Anupam Basu's Avatar
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  6. #26

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    Quote Originally Posted by michaelbsc View Post
    I'm not so sure that something that old would have been 1/100 for the instantaneous setting. Clearly this is "just a guess" on my part, but I'd bet it was closer to 1/20 or 1/25 for the film speeds of the day, particularly if it has a fixed f/12.5 aperture.

    Of course that doesn't mean a thing about what it currently fires. However it can't be a complicated mechanism, so getting it back in proper order should be possible, especially if it works now. Clearly all the parts are there an not broken if it fires.

    MB
    yup, just a guess.
    an educated guess from the days when i used to fix and use and resell falling plate cameras ...
    ... and other "stuff" that used a guillotine shutter.

    YMMV

    john
    Last edited by jnanian; 09-14-2008 at 01:26 PM. Click to view previous post history.

  7. #27
    ic-racer's Avatar
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    Quote Originally Posted by bobwysiwyg View Post

    Any sense for what the level of accuracy, +/-, one might expect after a professional servicing?
    The specs given in my COMPUR repair manual state 15% tolerance for speeds 1 to 1/125 and 20% tolerance for 1/250 and 1/500

  8. #28
    bobwysiwyg's Avatar
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    Thanks, both helpful and comforting.
    WYSIWYG - At least that's my goal.

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  9. #29
    bobwysiwyg's Avatar
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    Nikon FM Shutter Test

    Having used "the gadget" to check my 4x5 shutters, thought I would start checking my 35mm bodies. Just did the Nikon FM and the accuracy was pretty amazing considering their age and past use. I'll do my FE and an even older Pentax SV when I get time.
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