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  1. #11

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    I just thought of something. An upside down focus screen would produce exactly the opposite problem than the one I am having. The film plane would be closer to the lens so the subject in focus would be beyond where the taking lens is focused.
    A politician is a man who will double cross that bridge when he comes to it.

    Oscar Levant

  2. #12
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    Hi pbromaghin. Check out my comprehensive suggestions in the last two posts in the thread beginning here http://www.apug.org/forums/forum51/7...ml#post1322255. They should assist anybody attempting to fix/calibrate their TLR's focus (I used a Mamiya C330).

    regards
    Peter
    Last edited by PeterB; 10-16-2013 at 04:49 AM. Click to view previous post history. Reason: deleted some buggy formatting characters

  3. #13

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    Quote Originally Posted by PeterB View Post
    Hi pbromaghin. Check out my comprehensive suggestions in the last two posts in the thread beginning here http://www.apug.org/forums/forum51/7...ml#post1322255. They should assist anybody attempting to fix/calibrate their TLR's focus (I used a Mamiya C330).

    regards
    Peter
    Thanks, Peter. Reading that made me feel your pain. This corresponds closely with other advice I have gotten outside this thread. I'm going to show your last 2 posts to my repair guy, It's starting to look like a good idea to buy a repair manual, too.
    A politician is a man who will double cross that bridge when he comes to it.

    Oscar Levant

  4. #14

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    yeah it sounds like a classic case of the foam underneath the focussing screen deteriorating. I'm pretty sure my comments are in PeterB's thread. I would suggest starting with examining the foam of the screen First before messing with anything else.

  5. #15

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    Quote Originally Posted by RidingWaves View Post
    yeah it sounds like a classic case of the foam underneath the focussing screen deteriorating.
    Oooooh. I hadn't thought of it that way. Makes a lot of sense.
    A politician is a man who will double cross that bridge when he comes to it.

    Oscar Levant

  6. #16

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    Revisiting this

    My repair guy just can't be convinced there is a problem. I even showed him a roll that I shot to diagnose the problem. Does anybody see any big hole in this procedure?:

    Taking a clue from PeterB above, I set the camera on a tripod at 45 degrees from the brick front of my house with the sun at an angle to create lots of texture. I put several lengths of tape on the wall, vertically at 6-inch intervals. I then took 12 shots, 1 each for the f/80, f/105, f/135 and f/180 at 5 feet, 10 feet and 15 feet, all at maximum aperture.

    After developing the roll, I examined it with a loupe on the light box and guestimated the difference between the target and the actual focus plane (a2 + b2 = c2). I then plugged these guestimates into the focal formula 1/lens focal length = 1/subject distance + 1/image distance. I figured that with 12 data points, even if some of the m are off, the aggregate will be better than what I have now.

    I haven't calculated all the data points yet, but so far the average appears that I need a 1 mm shim under the ground glass. I plan to order a C-33 repair manual this week on eBay.
    A politician is a man who will double cross that bridge when he comes to it.

    Oscar Levant

  7. #17

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  8. #18

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    Nice link. Thank you, Xmas. I haven't opened the camera up myself yet. I am reluctant to do so until I have the repair manual in hand.
    A politician is a man who will double cross that bridge when he comes to it.

    Oscar Levant

  9. #19

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    Undo the knob at rear of screen hood and lift off the screen hood.
    As documented in user manual...

  10. #20

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    Just to clarify: How did you measure the 5, 10, and 15ft distances? Measure from the central subject marker to a point on the camera, or using the focus scale? I am assuming the physical tape measure method, otherwise you have a secondary variable in the mix.
    I feel, therefore I photograph.

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