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Thread: How to measure the register of a film back

  1. #11
    Pete Oakley
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    Re: How to measure the register of a film back

    MPP's own brand 4x5 film holders are not that hard to find in the UK and these are the non standard register as far as I can remember. As you haven't said what country you're in this might not be much help.
    Pete.

  2. #12
    Jim Jones's Avatar
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    Re: How to measure the register of a film back

    Quote Originally Posted by LetterBeacon View Post
    . . . how can I tell if I have the early or later version of the MicroPress?

    Any help would be much appreciated!
    According to the 2005-2006 McKeon's camera the perhaps scarce initial 1950 MPP Press Camera was adapted from the metal bodied MPP technical camera. It was superseded in 1951 by the MPP Micro-Press with serial numbers starting with 3000. Its body was leather covered mahogany and the rangefinder was built into the top of the body. It included a focal plane shutter with instantaneous speeds of 30-1000.

  3. #13

    Re: How to measure the register of a film back

    Thank you everyone for your replies!

    I've asked on the MPP forum, but for some reason my posts aren't turning up on their forum - perhaps I need to be approved by a moderator first.

    Thanks for the table - that's still in the members area on the MPP Club site - I just need to work out if mine is the early or late version I guess!

  4. #14

    Re: How to measure the register of a film back

    Quote Originally Posted by Pete Oakley View Post
    MPP's own brand 4x5 film holders are not that hard to find in the UK and these are the non standard register as far as I can remember. As you haven't said what country you're in this might not be much help.
    Pete.
    I'm in the UK, so I might be able to find them. Trouble is, MPP seemed to use their own standard and then adopted the International Standard later, so not all 4x5 MPP holders are guaranteed to be be the non-international standard.

  5. #15
    Jac@stafford.net's Avatar
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    Re: How to measure the register of a film back

    Just measure and if necessary shim to international standards. It is that simple.
    .

  6. #16

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    Re: How to measure the register of a film back

    For a lot of 4x5 uses, due to a working aperture of f/22 or f/32, the spec and perfect focus may not prove so critical. I expect that's why some folks responding to this thread are dismissive of a few thousandths of an inch. OTOH, with any new camera, and especially if you're trying to do something like use an Aero Ektar or other portraiture lens wide open (like trying to calibrate a split image rangefinder) it surely can be critical. Also, anytime you have a problem with attaining sharpness with a new camera, you'll want to eliminate all the variables, and this is certainly one of those several things to double check.

    There are several machinist's tools that are useful (quite nearly essential) if you're working with old cameras. A dial indicator one of these, a digital caliper is another.

    Bunches of film holders in circulation are of an earlier era, many used ones something like 30-75 years old. so it's a good idea to not just examine them for light leaks but to see if they're worn out or otherwise trashed. Fortunately, measuring them is relatively easy.

    When I was checking for flatness/warpage of film holders and backs, a cheap dial indicator on a standard "magnetic" base (weighted) is what I used since I happened to have them already. The set-up can be found for something like $30 USD at Harbor Freight Tools. For measuring individual film holders, a polished granite countertop would be an ideal surface, but any smooth counter-top should be sufficiently flat. Measure the difference from the front surface of the holder to the film pocket at several spots across each to get a sense of whether the holder is warped--the clean, polished granite surface makes it easy.
    Note that the actual film-plane register is a published specification; it takes into account the thickness of the film emulsion.

  7. #17
    Jim Jones's Avatar
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    Re: How to measure the register of a film back

    Quote Originally Posted by Ivan J. Eberle View Post
    . . . Note that the actual film-plane register is a published specification; it takes into account the thickness of the film emulsion.
    That dimension (the "T" dimension) is measured from the face of the film holder to the back of the slot in which the film slides. For 4x5 film holders, this distance is 0.197" +/- 0.007". It ignores the thickness of the film as it should in a standard for film holders. The minimum dimension of the slot (the "H" dimension) is 0.012". Curvature of film can exceed these dimensions. Even if the film is perfectly flat, there is enough slack within these specs to affect image sharpness with fast lenses. Anyone concerned with the critical distance between lens and film surface should research the matter according to their own needs rather than rely on what others may use.

  8. #18
    Jac@stafford.net's Avatar
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    Re: How to measure the register of a film back

    If we wish to get anal about this look to aerial film cameras which use a a perfect glass plate with fiducial markings that presses against the film.

    You cannot do this at home and if you tried it would be in vain. If you succeed to make perfect focus nobody would notice.

  9. #19

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    Re: How to measure the register of a film back

    Quote Originally Posted by Jac@stafford.net View Post
    If we wish to get anal about this look to aerial film cameras which use a a perfect glass plate with fiducial markings that presses against the film.

    You cannot do this at home and if you tried it would be in vain. If you succeed to make perfect focus nobody would notice.
    Some aerial cameras. But virtually all photogrammetric cameras use the glass plate and fiducial crosses.

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