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Thread: Is my lens bad?

  1. #11
    Kevin Kehler's Avatar
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    This might sound like a stupid suggestion but I had noticed a significant drop in sharpness of prints about a year ago. I thought that perhaps the lens elements were loose or the focus screen was off; turns out one of my eyes made a significant change in prescription strength and since I used that eye to focus, the pictures were off. My eye doctor said these changes can happen suddenly or gradually. A $100 visit to the optometrist might save a $500+ camera repair if you haven't had your eyes checked recently.
    Once a photographer is convinced that the camera can lie and that, strictly speaking, the vast majority of photographs are "camera lies," inasmuch as they tell only part of a story or tell it in a distorted form, half the battle is won. Once he has conceded that photography is not a "naturalistic" medium of rendition and that striving for "naturalism" in a photograph is futile, he can turn his attention to using a camera to make more effective pictures.

    Andreas Feininger

  2. #12
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    Kevin , it's not a stupid suggestion : I have solved a focus problem with -3d eyepiece correction lenses , because I don't like to use glasses while photographying .

    An other suggestion : many lenses don't give sharp images at full aperture and it's better at f:5,6 and more .
    Perhaps some tests at several apertures could give some information...
    (I say that , but I have a 50mm Sekor RB67 C lens which is bad at f:4,5 and also bad at f:8...)
    Last edited by Andy38; 09-16-2008 at 03:20 AM. Click to view previous post history.

  3. #13
    noumin
    I have nothing to offer than a few stupid questions and suggestions :

    - If you use an "N" Type lens you should be ok with DOF. The DOF-Scales on the older non "N" lenses
    were way to optimistic.
    - Do you use a waistlevel finder and if so, do you use the loupe for focussing ?
    - You're not using 120 film with a 220 back ? I don't know if this is technically possible but who knows.
    - Just for comparison, use a tripod or put the camera on a wall or chair or what's available
    for a shot, and then mirror up, cable release and see if this helps.
    - Check if the groundglas is properly seated.
    - Do the negatives actually appear sharp ? It seems you make your own enlargement, it could as well be, that
    there is something going wrong there. And yes more contrast does make prints appear sharper.

  4. #14

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    Not my eyes--still 20/20 and I shoot a Nikon with a plain focusing screen rather than the rangefinder in the Mamiya, which makes focusing easier (and I have also shot at infinity with no sharpnes anywhere). Not the aperture--occurs at f8 and f16. It's a later N model lens. I use the eye level prism, not a waist level finder. Enlarger is fine for other formats and cameras.

  5. #15
    Ian Grant's Avatar
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    Before you do anything else check the lens focus like I suggested early. If you don't have a glass screen to put across the film plane then waxed paper used in cooking or tracing paper will work just tape it tight. Put the camera on a tripod focus on something using the normal screen/prism finder then fire the shutter on B and see if the image is sharp at the film plane.

    Ian

  6. #16

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    Ian, how do I get the wax paper in/on the film plane. the body doesn't have a removable back, so the film plane is inside the body. Thanks.

  7. #17
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    If the image on the ground glass looks sharp, it must be the ground glass or the mirror which is the culprit, it seems to me.
    John, Mount Vernon, Virginia USA

  8. #18

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    As a comment on your G1 and G2 difference, that could well be the contrast effect creating a "perceived" increase in sharpness. This is not real and is more about how the eye resolves images. Is the improvement of the sharpness perceptible in areas of continuous tone or are you perceiving it at the edges (more likely to be related to contrast increase?)

    If it was me, i would set up a controlled test with the existing lens, set to infinity, and also close up, with an f-stop set two stops down from fully open on a tripod. I would then pay a visit to a shop with exactly the same film and set-up in camera and take a couple of pictures with a new lens, on the pormise to the shop that you want to check out the lens before buying it...if all the pictures are the same after development, then you may be looking at a viewing screen or maybe even a film plane issue...

    Finally...are you sure the sharpness is not lost in the printing stage....?

    K

  9. #19

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    Shangheye, the sharpness is on egdes and I agree with you that this is probably perceived sharpness due to contrast. Also, I'm in luck for testing because a friend works at a local store and I can try any of the bodies. lenses, and prisms for free. No explanations needed. Lastly, I don't believe the sharpness is lost at the printing stage but I will be trying a news enlarger lens tomorrow. That is the only variable at the printing stage.

  10. #20
    Ian Grant's Avatar
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    Quote Originally Posted by jmal View Post
    Ian, how do I get the wax paper in/on the film plane. the body doesn't have a removable back, so the film plane is inside the body. Thanks.
    That's a very good point, it's about10 years since I tested my 645J - I had an unmounted focus screen and used that. It showed that the focus screen was significantly out on my camera.

    As you can get your friends help get the store to have a look for you.

    Ian

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