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Thread: Flange focal distance for lenses mounted in Prontor shutters

  1. #21

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    Re: Flange focal distance for lenses mounted in Prontor shutters

    Sure, having the gg can be used to our advantage too. Putting the focus helix at a shorter than infinity FFD and then just focusing correctly the infinity at the gg, even marking the newly found infinity at the focus helix is also a possibility. Then you don't even need to check the gg, the marking is sufficiently precise (as even eventual 1 or 2 over turning of the helix translates to a very minimal FFD change, precise enough.)

  2. #22

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    Re: Flange focal distance for lenses mounted in Prontor shutters

    Quote Originally Posted by Jac@stafford.net View Post
    (the cherry-wood body was made to mm accuracy by my friend, Don, on his micro-precision planer with my suggestion for a mm adjustment of my choice which was to be 2mm short of ideal, the rest to be made up with a back gasket.)
    While thinking of it - what you said, should be written in golden letters! As a warning to all those who want to build a camera thinking that it is enough to know the FFD and then build a box of the right thickness for it.
    In reality, it is very difficult to measure all the parts that make that box and to make it precisely for the given FFD without falling in some practical difficulties on the way (see the OP). Even more so, when installing a 35mm lens as the OP wants. That lens will need very precise plan parallelism difficult to achieve at once with all the parts involved.
    An adjustable construction is necessary in amateur manufacturing.

  3. #23
    Jac@stafford.net's Avatar
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    Re: Flange focal distance for lenses mounted in Prontor shutters

    I am thinking of Dan From's many posts which concern his experience with military RECON cameras and lenses. A very good friend of mine was an air recon tech who dealt with Voodoo and U2 films. He was always impressed with the camera and lens technology and he added, "Nothing can replace the photo interpreters..." The human's capacity then (the Sixties) could recognize and accommodate lenses ever-so-subtle errors. But that was before digital.

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