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Thread: How tightly should film back fit in the camera?

  1. #1
    jvuokko's Avatar
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    How tightly should film back fit in the camera?

    I have noticed that one of my Toyo monorail cameras has alignment error, the plane of ground glass (and whole film back assembly) differs from the plane of the back frame.

    When the back and GG is aligned to vertical, the back frame shows some tilt.

    I have seen the slight out of focus portions in some negatives, but have always thought that it's just my mistake. Now after found that alignment difference, I checked my other monorail cameras.

    The 810G and 45G does not have problems with GG plane - rear frame alignment. But while checking these, I noticed another thing; the back on every camera has some freeplay. Horizontal and vertical.

    Is this normal or should I do some shimming? The amount of movement is demonstrated in this video clip.


    The GG to rear frame alignment must also be fixed - is this done with some kind of shims or how?


    Thanks for your help
    Jukka Vuokko
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  2. #2
    Unwitting Thread Killer Ari's Avatar
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    Re: How tightly should film back fit in the camera?

    Jukka,
    Some play is normal on these cameras, especially if they have seen some use.
    This does not affect much, just make sure that the back is in the same position when focusing as when shooting.

    As for aligning the GG, Toyo Gs don't normally use shims, the glass rests directly on the metal protrusions that are built into the frame.
    You'll have to find out why it sits at an angle, and make adjustments accordingly, but make sure you refer to the metal protrusions as the zero setting; that is the plane where the film will sit.
    I hope I made enough sense.

  3. #3
    jvuokko's Avatar
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    Re: How tightly should film back fit in the camera?

    Thanks!

    Good to know that some freeplay is normal

    The Alignment problem - So far it seems that it's caused by rear standard's inner part (where you attach the film back and/or bellows).
    When GG and inner part is aligned properly with lens board and front standard, the rear standard has ca. 2 degree backward tilt and some swing.
    Jukka Vuokko
    Flickr

  4. #4
    Unwitting Thread Killer Ari's Avatar
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    Re: How tightly should film back fit in the camera?

    Can you post photos?
    It sounds very strange.

  5. #5
    jvuokko's Avatar
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    Re: How tightly should film back fit in the camera?

    Quote Originally Posted by Ari View Post
    Can you post photos?
    It sounds very strange.
    First measurements were done by using mainly calipers and then calculating the angles.


    Now I got digital protractor (not sure how accurate, but better than bubble lever).


    The initial measurements confirms that there is alignment difference between the rear frame's top part and the inner part.

    The difference is approx. 1 degree when all settings are zeroed. This can be corrected by shimming top bubble levers.


    However I found something more confusing.

    When the monorail is aligned horizontally, the rear (and front) frames are tilted 2,5 degree backward!
    At the GG, this is about 2,2 degree backward tilt. The lens board on the front has similar tilt (+/- 0.1 degree).


    So the confusing part is now: Why both front and rear frames aren't directly 90 degree angle against the monorail, but are instead tilted backwards?


    Here's photo with illustrations:

    Jukka Vuokko
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  6. #6
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    Re: How tightly should film back fit in the camera?

    It looks like that when the machine operator who did the dovetails did not indicate the standards very well.
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  7. #7
    jvuokko's Avatar
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    Re: How tightly should film back fit in the camera?

    The more I check, the more I found inaccuraties.

    As the frames aren't perpendicular to monorail, the swing is also flawed. When read and front frame are zero swing position (there's detent), they have actually some degree misalignment.
    With old credit card align check, when the left edge of (inner) frames are set to distance of a credit card, then the right edges has distance of a credit card plus some 3-4 millimeters.


    I guess that this is just a badly built? And only fix is to mark my own corrected zero positions for tilt and swing.


    Here's shown how much the plane of rear frame differs from vertical:
    Jukka Vuokko
    Flickr

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    Re: How tightly should film back fit in the camera?

    The standard already seems significantly off angle to the base rail - the frame only alters that by 0.2. I don't think that camera can possibly have been sold in that (poor) shape - the maker, importer, shop and buyer should all have noticed such a glaringly obvious flaw. This is either the result of a clumsy repair (or combination of parts from two poorly matched cameras) or the standard got bent in a drop.

  9. #9
    jvuokko's Avatar
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    Re: How tightly should film back fit in the camera?

    I aligned both frames horizontally and vertically. Took also zero position detents off.


    It's mystery to me how both standards are so much off angle to the base rail, and similary.
    Perhaps it's poorly repaired or something. I haven't seen many pictures of similar cameras, so it's hard to tell if there's something that clearly isn't original part.
    Jukka Vuokko
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  10. #10

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    Re: How tightly should film back fit in the camera?

    Is the dovetail slot gibbed? From the picture it looks like there is an adjustment plate or shim in the dovetail slide that is wedging the whole rear standard assembly out of plumb.

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