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  1. #1

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    Need help diagnosing an odd problem

    Hi everyone,

    Didn't know where best to put this so I'm posting in this wedding section

    I've been shooting wedding recently almost entirely on film and have had quite a lot of success, especially with black and white film and medium format color (using a Pentax 645).

    However, I recently ran into an issue where one of cameras/lens with color film would strangely cause part of the image to darken and sometimes just downright underexposure the image.

    Attached is a sample here of where the image was strangely darkened. And no, that's not my finger.

    Click image for larger version. 

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    It usually happens when it's really sunny. The camera setup is as follows:

    Nikon F3
    Nikon 35mm F1.4 Ai-S (or Ai).
    Usually high shutter speed of 1/2000 or 1/1000.
    I have a neutral density filter on those times (usually). The ND Filter is mounted by progressive step-up rings so the step-up rings look like a cone (52->55, 55->58, 58->etc etc until I get to 77, the size of the neutral density filter.

    Portra 400 color film used.


    Any suggestions? I'm very puzzled...

  2. #2
    MattKing's Avatar
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    It looks like vignetting to me.

    Do you use a lens hood?

    Is there a strap on the camera?

    Is the shape of the cone not wide enough for a 35mm lens?
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  3. #3

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    I'd say the shutter slit is changing speeds on you. IOW, the shutter is erratic.

  4. #4
    Andrew K's Avatar
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    Does this happen with other lenses at the same shutter speeds?

    My initial reaction is that you have a shutter problem where the curtain speeds are not accurate, and the 2nd curtain is firing early and causing "capping" of a part of the exposure (think setting the shutter at the wrong flash sync)..

    Do some test shots if you're not sure, but thats my guess based on years of repairing cameras
    A camera is only a black box with a hole in it....

    my blog...some film, some digital http://andrewk1965.wordpress.com/

  5. #5

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    There's a strap on the camera but I'm quite sure it wasn't in the way.
    The "lens hood" is more like this setup, with an ND filter on it. It's so I can use my 77mm ND filter with a 52mm thread lens.
    http://canong11.amirw.net/prevent-vi...-58mm-adapter/

    I have some images with vignetting and it occurs around the edges. This I notice and can pretty easily diagnose. However, this is different.

    I'm beginning to think that maybe it does have to do with the camera body itself. I've been testing on a Nikon D40 with the lens and ND filter and haven't had any issues creep up. Will definitely shoot more test images but would like to see if there's any more suggestions.

    Kinda sucks this happened during a wedding. Thankfully, it was 1 of 3 cameras.

  6. #6

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    It's the shutter. Time for CLA, or stay below 500. There's no sane need for these superfast shutters in the first place.

  7. #7
    MattKing's Avatar
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    Quote Originally Posted by dugrant153 View Post
    There's a strap on the camera but I'm quite sure it wasn't in the way.
    The "lens hood" is more like this setup, with an ND filter on it. It's so I can use my 77mm ND filter with a 52mm thread lens.
    http://canong11.amirw.net/prevent-vi...-58mm-adapter/

    I have some images with vignetting and it occurs around the edges. This I notice and can pretty easily diagnose. However, this is different.

    I'm beginning to think that maybe it does have to do with the camera body itself. I've been testing on a Nikon D40 with the lens and ND filter and haven't had any issues creep up. Will definitely shoot more test images but would like to see if there's any more suggestions.

    Kinda sucks this happened during a wedding. Thankfully, it was 1 of 3 cameras.
    Isn't the D40 a cropped sensor camera? If so, the "sensor" size is a lot smaller than 35mm film, so I'm not sure it will serve as a reliable test for vignetting on "full frame" film.
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  8. #8
    MattKing's Avatar
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    Quote Originally Posted by Tom1956 View Post
    It's the shutter. Time for CLA, or stay below 500. There's no sane need for these superfast shutters in the first place.
    If it is the shutter, it looks to me like the shutter has a curved edge.

    I'd suggest putting the multi-stage adapter on with a fairly transparent 77mm (UV or skylight??) filter of similar physical size and then using depth of field preview plus a smaller aperture to see if you can see any vignetting.

    Some ground glass at the film plane with an open shutter may also allow you to see what is happening.

    The Canon G11 article you referenced deals of course with a camera sensor that is about the size of a fingernail - the conditions that lead to vignetting change with real focal lengths and sensor sizes. It may be that a 35mm lens used with 35mm film needs a "steeper" adapter.
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  9. #9
    lxdude's Avatar
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    Quote Originally Posted by MattKing View Post
    If it is the shutter, it looks to me like the shutter has a curved edge.
    I think that look is due to more light at the horizon. I think it is a shutter curtain issue.
    I do use a digital device in my photographic pursuits when necessary.
    When someone rags on me for using film, I use a middle digit, upraised.

  10. #10
    markbarendt's Avatar
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    I'm thinking along the same lines as camera strap, finger.

    Buddy of mine was having the same Lind of problem, had him show me how he held the camera, sure as sunrise he was letting a finger get in the way.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

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