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Thread: Is my lens bad?

  1. #1

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    Is my lens bad?

    Let me preface this by saying that I don't have prints scanned and I'm not sure it would be apparent in a low quality scan anyway. So, here's my problem. I have a Mamiya M645 1000s that I have owned for 7 months, but have run very little film through. Perhaps 6 rolls. I never can get what I consider to be a sharp image, even at 8x10. Some prints are just barely tolerable, but most are clearly not in focus--anywhere. Even when shooting objects at a distance and the focus is set to infinity. Keep in mind that I am shooting static objects handheld at shutter speeds no lower than 1/125 on an 80mm lens. The lens is one of the later 80mm models. At first I thought it was just the lack of DOF associated with MF. However, I have seen plenty of photos in MF that have reasonable DOF. And please don't say "it's not Zeiss glass" because Mamiya lenses are perfectly capable of getting sharp images. Any thoughts? I am going to try to borrow a friend's lens to see if the results differ, but I figured I'd ask here too. Oh, one more curiosity. I printed one photo at grade 2 and it looked adequate. Then, I printed it at grade 1 to get more tone in the sky and the G1 looks OOF while the G2 appears more focused, though not super sharp. Thanks.

    Jmal

  2. #2

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    I don't know that camera, but I have been thinking about optics for 40 years. Borrowing a friend's lens seems a great way to trouble-shoot the problem. I bet the lens is normally capable of razor-sharp negatives. Your method of shooting at infinity is a good one, too. The viewfinder screen may be out of place - although you have wisely bypassed that cause by your infinity method.

    Is it possible that the lens isn't in the designed location? - i.e. slightly ahead with a mis-fitted lens attachment flange, for example. It must be small distance if that is the problem.

    Perhaps the lens requires an overhaul. I can imagine something being amiss there, without knowing exactly what it might be.

    Looking at the negatives with a magnifier should remove any doubt of sharpness. With my Rolleicord, on ACROS film, I photographed my daughter's boyfriend, on his bike, from about 12 feet away. I could see a myriad of his leg hairs on the negative, and these didn't survive [low-cost] scanning and digital printing.

    Is it possible that the film isn't in the correct place? A few thousandths of an inch error and images would not be sharp. If you could borrow a ground glass, and hold it against the film guide rails, that will show if the lens is forming the image in the correct plane.


    I imagine that when you solve the problem, the negatives will be stunningly sharp. My best wishes.

  3. #3

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    LM--the lens has no other attachments and is mounted correctly. As for the film location, there is no other place it can go. It's a pretty simple mechanism. And, the film is wound snugly againt the pressure plate, so it should be flat. We'll see what another lens changes, if anything. Thanks.

  4. #4

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    I would double check the seating of the focusing screen under the finder. It may be not seated fully and locked in place.

  5. #5

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    I will double check it, but I believe it is seated well. It sort of "snaps" into place. It's definitely worth checking, but how about the shots at infinity? They should have [I]something[I] in focus.

  6. #6
    phenix's Avatar
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    Did this lens pass a CLA before you used it? If yes, than it is very possible that an element was mounted reversed. Usually it is the case of a quasi-symmetric element. I’ve bought once a 50/1.4 lens (35mm format) that showed the same symptoms you are explaining here, including the error to focus at infinity. I took it apart, and reversed an element that looked quite symmetrical, but of course wasn’t. After this operation, my lens worked perfectly. Just a suggestion.

    Anyway, as said before, if your lens doesn’t focus at infinity, your troubles are not from the focussing screen. Leave it as is, don’t introduce another variable in this equation.
    B&W is silver.

  7. #7

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    The quickest road to Rome=get another lens: if this will focus sharply on your negative (forget the print) you can be happy about the body and the mount. If not, then try a different back as the next step. I have seen a dropped camera (landed nose down) where the mount snapped in nicely but the flange was very slightly buckled. This was evident on inspection of image on ground glass (actually the poor man's trick of scotch tape across the film gate) as only a part of the image would come into focus.

    Very frustrating for you because this camera is quite capable of excellent results.

  8. #8

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    Thanks for the advice. As for the CLA, it could have been done before I bought it, but I have no idea. I bought the kit from KEH in EX+ condition, so it all looks good. I don't see any evidence of damage to the body or mount. We'll see how another lens works out. If it looks good, I will just geta new lens. They are probably cheaper than sending a camera for repair.

  9. #9

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    You could always check the collimation of the lens using an SLR and a telephoto lens. It's fairly simple to do, and it will tell you a lot about whether the Mamiya lens is sharp at infinity.

    When checking collimation, the lens should reach its sharpest point when it's at infinity.

    Also, is it possible for you to try that lens on another body?

  10. #10
    Ian Grant's Avatar
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    Get the camera checked out, it is possible the screen is off register. I have a 1000s and a 645J and I noticed the 645J body wasn't sharp at wider apertures. I placed a ground glass screen across film plane with the camera back & shutter open and cross checked with the focussing screen and it was out of register, so it was corrected and was fine afterwards.

    Once it is sfixed make sure that you use the MU - mirror up - option whenever you use the camera on a tripod, this prevents mirror slap and the resulting images are significantly sharper.

    Ian

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