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Thread: Is the nominal shutter speed listed on the Calument tester correct?

  1. #31
    8x10, 5x7, 4x5, et al Leigh's Avatar
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    Re: Is the nominal shutter speed listed on the Calument tester correct?

    Quote Originally Posted by Pfsor View Post
    If I remember well, the 555 runs on 0.1 MHz. Enough to measure to 1/100000 s. And yes, the 555s are used in time measuring devices (with a 4026 to count the oscillation). You can always strive for better. Besides, there is no meaning to use 16-200MHz crystals to measure times long at most 1s. Not in a device with possible errors from off centre position!
    My but you can sure cram a lot of mis-information into a few sentences.

    The highest possible frequency for a 555 would be defined by the rise time + the fall time of the output waveform.
    Those are each 100ns, so 200ns total, which is a frequency of 5MHz.
    Of course in a real circuit you could never achieve such fast operation reliably, but you can get to 1MHz.

    The problem with the 555 is that it uses external resistors and capacitors to set its operating frequency.
    While precision resistors are readily available, capacitors better than 5% are very difficult to find.
    Add to that the switching time errors within the device, and you'd be lucky to hold 6% without high cost.
    The actual 555 timebase circuits I've encountered usually spec their accuracy at +/-10%.

    I've never encountered any crystals that operate at 200MHz.
    Perhaps such do exist, but I've never found them in any equipment I've worked with.

    And the position of the sensor has nothing to do with the measurement of exposure time.
    A good time meter has three sensors, one in the middle and a pair at diagonally opposite corners.
    This allows you to get three times for each test, regardless of the direction of shutter movement.

    - Leigh

    Ref: 555 datasheet from TI: www.ti.com/lit/ds/symlink/lm555.pdf
    If you believe you can, or you believe you can't... you're right.

  2. #32

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    Re: Is the nominal shutter speed listed on the Calument tester correct?

    Leigh, you try hard, don't you? Of course you can use overtone with 555 but the normal frequency it runs on is 0.1 MHz. And whatever you say, 555 are widely used for time measuring. Some of us need the precision down to 1/millionth of s for measuring shutter speeds, and some of us use their Calumet testers.
    To each its own. Leigh is after "the absolute" precision. When was the last time you saw a Calumet tester with 3 sensors? In your dreams perhaps.

  3. #33

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    Re: Is the nominal shutter speed listed on the Calument tester correct?

    Quote Originally Posted by Leigh View Post
    I've never encountered any crystals that operate at 200MHz.
    Perhaps such do exist, but I've never found them in any equipment I've worked with.
    - Leigh
    Don't despair Leigh, there is always something new you can learn in the life. For a starter, try to google "200 MHz crystal oscillator". It could be your first encounter with the beast, who knows.

  4. #34

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    Re: Is the nominal shutter speed listed on the Calument tester correct?

    After this exchange I became more curious about the Calumet shutter tester (which I own) and decided to see its old manual. Rightly so, the tester has 1 light sensor only and among many possible error sources when used is also indicated the precise alignment between the sensor (the tester itself) and the shutter.
    A very interesting reading and it can be found on the net also. Recommended to all who are interested to know more about this shutter tester. (There is also a detailed explanation to the OP's question.)

  5. #35

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    Re: Is the nominal shutter speed listed on the Calument tester correct?

    Quote Originally Posted by Pfsor View Post
    After this exchange I became more curious about the Calumet shutter tester (which I own) and decided to see its old manual. Rightly so, the tester has 1 light sensor only and among many possible error sources when used is also indicated the precise alignment between the sensor (the tester itself) and the shutter.
    A very interesting reading and it can be found on the net also. Recommended to all who are interested to know more about this shutter tester. (There is also a detailed explanation to the OP's question.)
    I own three Calumet shutter speed testers. When testing a shutter I test each speed three times because every once in a while the meter in error will give me the wrong speed. Sometimes it's the meter I think and sometimes it's user error on my part.

    I've found that it's also a good idea to "warm up" the shutter by firing it a few times at all speeds before testing.

  6. #36
    8x10, 5x7, 4x5, et al Leigh's Avatar
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    Re: Is the nominal shutter speed listed on the Calument tester correct?

    Quote Originally Posted by Pfsor View Post
    When was the last time you saw a Calumet tester with 3 sensors? In your dreams perhaps.
    I was talking about real shutter testers, not oriental toys.

    - Leigh
    If you believe you can, or you believe you can't... you're right.

  7. #37
    8x10, 5x7, 4x5, et al Leigh's Avatar
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    Re: Is the nominal shutter speed listed on the Calument tester correct?

    Quote Originally Posted by Pfsor View Post
    For a starter, try to google "200 MHz crystal oscillator". It could be your first encounter with the beast, who knows.
    Why do you insist on talking about subjects with which you have no knowledge whatsoever?

    In my earlier post, I said "crystals operating at 200MHz", NOT "crystal oscillators".

    Since you obviously do not know the difference, why are you running your mouth?

    - Leigh
    If you believe you can, or you believe you can't... you're right.

  8. #38

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    Re: Is the nominal shutter speed listed on the Calument tester correct?

    Quote Originally Posted by Leigh View Post
    I was talking about real shutter testers, not oriental toys.

    - Leigh
    Still trying hard? Ever noticed the title of this thread? Can you read?

  9. #39

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    Re: Is the nominal shutter speed listed on the Calument tester correct?

    Quote Originally Posted by Leigh View Post
    I was talking about real shutter testers, not oriental toys.

    - Leigh
    Way to make a racially based buying decision!
    Bill
    "There are a great many things I am in doubt about at the moment, and I should consider myself favoured if you would kindly enlighten me. Signed, Doubtful, off to Canada." (BJP 1914).

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