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  1. #1

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    Another Pentax 67 problem...

    A new problem with my Pentax 67. Putting the speed at 1 second caused a strange shutter problem today, one that gave me no choice but to waste half a roll trying to figure out what was going on. When I put the shutter dial at 1 second and pressed the MLU switch, the aperture blades stopped down to f/22 (correctly), for about a second (judging by ear), then the mirror went up and the blades opened up again. Then, upon pressing the shutter, the the mirror went down immediately, leading me to believe the MLU switch made the exposure. How can this be!?

    I can't believe how mischievous the 67 is. After unloading the wasted roll when I got home, I tested the camera in dry mode at 1 second again with MLU engaged. Worked perfectly!
    Why does the shutter suddenly take on a life of its own when film is loaded?

  2. #2
    dpurdy's Avatar
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    Poltergeist! Has the camera seen heavy use in the past? They are very durable but eventually parts will start to wear out.

  3. #3

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    It was a college studio camera. I've recently got it back from a repair.

  4. #4
    Hatchetman's Avatar
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    did you change the lens right before by any chance? that sometimes messes things up.

  5. #5

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    I only have one lens so didn't change it. Very curious as to why the shutter only does this when film is loaded though.

  6. #6
    Poisson Du Jour's Avatar
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    Are you sure you are following the 67 at the moment of actual exposure? MLU comes first (initiated by you), then you shortly after, triggering the shutter and, by dint of that, stopping down the aperture blades. It is not in the realms of possibility for the process to be reversed or for MLU to emulate the shutter: it has no connection to the shutter; it's only connection is to the mirror with electrical connection to two solenoids to bring it up and magnets to throw it down. But...

    ...if the prism/lens reattachment process is not followed, unpredictable results can occur because the aperture coupling is not engaged, so there is no coordination between the lens aperture and the camera coupling. Remove the prism. Remove the lens (this resets the position of the aperture coupling to null. Then replace the prism. And replace the lens, in that order (this will link the aperture tang and coupling chain correctly). Load a dummy/exposed roll of film and go through the process carefully again.
    .::Gary Rowan Higgins

    One beautiful image is worth
    a thousand hours of therapy.


    "It is horrifying that we have to fight our own government
    to save the environment."
    .::Ansel Adams






  7. #7

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    Quote Originally Posted by Poisson Du Jour View Post
    Are you sure you are following the 67 at the moment of actual exposure? MLU comes first (initiated by you), then you shortly after, triggering the shutter and, by dint of that, stopping down the aperture blades. It is not in the realms of possibility for the process to be reversed or for MLU to emulate the shutter: it has no connection to the shutter; it's only connection is to the mirror with electrical connection to two solenoids to bring it up and magnets to throw it down. But...

    ...if the prism/lens reattachment process is not followed, unpredictable results can occur because the aperture coupling is not engaged, so there is no coordination between the lens aperture and the camera coupling. Remove the prism. Remove the lens (this resets the position of the aperture coupling to null. Then replace the prism. And replace the lens, in that order (this will link the aperture tang and coupling chain correctly). Load a dummy/exposed roll of film and go through the process carefully again.
    I followed your reattachment advice, loaded a dummy roll and everything went smoothly. But who knows what will happen when I shoot a new roll tomorrow!
    Is it really possible this coupling thing was causing the erratic shutter problem? If so, simply removing the lens before the prism can cause such a major problem, leading to lost frames? I just wonder how the camera could have been engineered in such a silly way.

    Today when I engaged MLU, the mirror didn't move immediately, there was a lag of about a second. Then when the mirror did move, the aperture blades opened fully rather than staying at f/22 as set. Then when I pressed the shutter, the mirror this time dropped immediately, even though the shutter dial was set to a second. That second pause when I pressed the MLU button led me to believe MLU made the exposure, as it was the only time in the process when there was a pause in the camera mechanism.
    Last edited by batwister; 09-21-2012 at 06:07 PM. Click to view previous post history.

  8. #8
    dpurdy's Avatar
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    The prism and lens order have to do with the meter working. If you happen to take off your prism with a lens on the camera and then put the prism back on the meter won't work. You have to have the prism on the camera and then put the lens on for the meter to work.

  9. #9

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    The prism I have is just the standard pentaprism, non-metered.

  10. #10
    Poisson Du Jour's Avatar
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    Yes, the prism needs to be coupled to the lens aperture lever or the mechanism will not engage and thus potentially snap the coupling chain — an involved and extremely fiddly repair job that is a bit like repairing a watch.

    Process is: prism off, then lens. Replace the prism, then re-mount the lens. Ensure the prism coupling pin engages positively with the shutter speed dial. If the prism has a switch, turn it on to verify the meter is reading at the selected aperture/shutter speed value (if in low light, switch to bulb and maximum aperture of lens: needle should shoot up to the top). If the prism has been correctly fitted/coupled, it is safe to change just lenses any time you wish.

    The prism is generally only removed to facilitate cleaning of the focusing screen.
    Last edited by Poisson Du Jour; 09-21-2012 at 10:16 PM. Click to view previous post history. Reason: grammatic correction
    .::Gary Rowan Higgins

    One beautiful image is worth
    a thousand hours of therapy.


    "It is horrifying that we have to fight our own government
    to save the environment."
    .::Ansel Adams






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