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  1. #1

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    Mamiya tlr focusing problem

    Please bear with me as this is complicated and difficult to explain clearly.

    The film plane does not agree with the ground glass on my C-33. When focused at 10 feet with the 80mm, the picture comes out focused at around 8 feet. The repair guy says the lens mounting bracket is bent so that the taking lens is just slightly farther from the film than the viewing lens is from the ground glass. He points to it not being exactly parallel with the main body when cranked all the way in. The difference from top to bottom of the mount is about 1 mm. However, when visiting Central Camera in Chicago I saw this exact difference on the other Mamiyas on their shelf. The sales guy said it was more likely that the lens assembly was out of line and suggested that I do a test with the other lenses.

    So I marked the front of my house with tape at 6" intervals, set the tripod up at distances of 5, 10 and 15 feet at 45 degrees from the wall, and took one shot at each distance with the 80mm, 105mm, 135mm and 180mm with the apertures at maximum opening. All shots showed the plane of focus to be some distance in front of the intended focus point. In each photo, the in-focus area is a small strip going straight from top to bottom.

    If the mounting bracket were indeed out of true then both lenses would point slightly upward, and wouldn't that be the same as a slight backward tilt in the front standard of a view camera? If so, I would expect the area of focus to move diagonally on the negatives, rather than straight up and down, due to the wall being at a 45 degree angle.

    Might I be lucky and only need the ground glass position to be adjusted with slightly thicker shims?
    “You seek escape from pain. We seek the achievement of happiness. You exist for the sake of avoiding punishment. We exist for the sake of earning rewards. Threats will not make us function; fear is not our incentive. It is not death that we wish to avoid, but life that we wish to live.” - John Galt

  2. #2

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    Easy to check,
    Use a ground glass at the film plane & set the focus, then adjust the screen to match.
    I haven't seen one in the flesh for years but most TLR's use either shims or a spring under the screen to allow adjustment with the corner screws.
    Heavily sedated for your protection.

  3. #3

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    John has hit it right on the head. Focus the taking lens to film plane.... The tune your viewing lens n screen.

    It's been a long time since I worked in a Mamiya TLR... either the viewing lens shims or the screen adjusts. I'll have dig my camera out to see it, but I don't have a c-33, I have the C-330 pro-s... I know some of these cameras had affixed screens.

    BTW there is a guy Graham Paterson is the expert if you Google him his site is very useful for these kind of problems.
    Anyone can make a Digital print, but only a photographer can make a photograph.

  4. #4
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    Do you have just the one lens? That makes it difficult to determine if the lens or camera is the problem. It's pretty hard for the lens to be wrong though because the lens board is just a metal board, it should be flat and the two lenses should be mounted in it identically. As you say, if the plane of focus is vertical then the front standard is probably not bent.

    I would expect that you just need more shims under the focus screen. I got a C220 recently with a similar but less severe issue - focusing about 0.8m short at 6m. A bit of extra shimming has it nicely aligned now and shooting about as sharp as I think that lens is capable of.

    Edit: finding appropriate shims is annoying unless you have a local hobby store with shim stock handy. I cut a strip out of a baked-bean can, measured it to be 0.2mm thick, drilled a bunch of holes in it and then cut my shims out with tinsnips.

  5. #5

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    Hello,
    is it possible with the C 33 to put in the viewing screen upside down?

  6. #6
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    Quote Originally Posted by jochen View Post
    Hello,
    is it possible with the C 33 to put in the viewing screen upside down?
    This is a good point. The focus screen is only ground on one side. If it is in backwards then your focus will be off. Has the camera been apart for cleaning?

  7. #7
    Rick A's Avatar
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    You may want to check to see if the rear elements of the lenses are screwed in properly.
    Rick A
    Argentum aevum

  8. #8

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    Ah focusing screen may be upside down... Good point.

    The dull side should be down.

    It would be nice to check another lens on there. It is also possible your lens may be a DIY fixer upper n shims were removed or viewing n taking lenses were swapped. Look for tool marks and the beauty ring will also say VIEWING N TAKING lens but that could have been swapped as well.

    But so far it seems everyone has given you every possabe senerio.

    Try another lens before adjusting anything.
    Anyone can make a Digital print, but only a photographer can make a photograph.

  9. #9

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    Propably the method for adjusting the focusing in manual for C220 will work: http://www.cameramanuals.org/mamiya_...pro_repair.pdf
    I've had some focusing issues with my Mamiya C220 and Mamiyaflex C2 cameras. The plastic focusing screen of C220 was slightly curved. Made adjusting shims (washers) with small punches out of a beer can.

  10. #10

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    Upside down focus screen... I'll have to check that.

    It has also been suggested to do a lens mount parallelism check and also to measure more exactly the difference in the subject focus distance and do the math to get the difference in image focus distance.

    I have strongly suspected all along that it's a shim problem. I did test with 4 different lenses at 3 distances and every one looked exactly alike so it seems to confirm this. Is there anything else that anybody thinks I should look for in the negs?

    Mike Butkus has the owners guide, but does anybody have a link to a C33 repair manual?
    “You seek escape from pain. We seek the achievement of happiness. You exist for the sake of avoiding punishment. We exist for the sake of earning rewards. Threats will not make us function; fear is not our incentive. It is not death that we wish to avoid, but life that we wish to live.” - John Galt

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