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  1. #1
    smieglitz's Avatar
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    Weird exposure problem

    One of the students in an Intermediate Photography course at the college where I work attempted a night photography assignment and her negatives exhibit a weird problem I have never seen before and am at a loss to explain. Throughout the roll and with different image locations, there is a faint inverted image of the frame that was being exposed superimposed on the main image. The faint image appears to be rotated 180 degrees from the main image rather than being a reflected mirror image. (See the attached print test strips. The image with the star has been manipulated so that rectangular part shows better on the scan.) She was using an older Canon AE-1 on "B" and bracketing exposures from 1 second out to 2 minutes at f/5.6. The foam padding around the viewfinder where the mirror seats when a image is being recorded on the film has deteriorated and is essentially missing. All I can think of is some faint image is somehow being reflected back and forth off the mirror or pentaprism surfaces because of that gap and ending up on the film upside-down.

    Any other ideas?
    Attached Thumbnails Attached Thumbnails camera problem marquee.jpg   camera problem star.jpg  

  2. #2
    cliveh's Avatar
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    She is bracketing exposures as you mentioned, but turning the camera round between exposures and the camera is double exposing (it's a Canon).

    “The contemplation of things as they are, without error or confusion, without substitution or imposture, is in itself a nobler thing than a whole harvest of invention”

    Francis Bacon

  3. #3

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    I had some ghosting/double images when scanning some of my high contrast slides. After initially blaming my lenses I found the film did not have the ghost image. It was coming from my scanner and internal reflections. Not nearly as bad as what you show though and not inverted either. That really is weird.

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    Poltergeist?

  5. #5
    smieglitz's Avatar
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    Quote Originally Posted by Lamar View Post
    I had some ghosting/double images when scanning some of my high contrast slides. After initially blaming my lenses I found the film did not have the ghost image. It was coming from my scanner and internal reflections. Not nearly as bad as what you show though and not inverted either. That really is weird.
    It's definitely on the negatives and throughout the roll. I also played around with it a bit in Photoshop and confirmed the secondary inverted image is the same size as the normal image, although it does not align perfectly when rotated 180 degrees. The angular relationship is the same but the secondary image is offset a little bit when rotated.
    Last edited by smieglitz; 10-02-2013 at 09:59 AM. Click to view previous post history.

  6. #6

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    Quote Originally Posted by smieglitz View Post
    It's definitely on the negatives and throughout the roll.
    So can you rule out cliveh's explanation?

    pentaxuser

  7. #7
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    I had this problem once in a similar situation - high contrast night shots (of St. Peter's Basilica and the Vatican, if anyone's interested).

    All I did to rectify this was make sure that I used the viewfinder cover before I took the shot - my only guess as to what caused this was internal reflections from somewhere within the pentaprism. The camera I was using was an AE-1 too, with a less-than-perfect mirror - maybe some light leaked through the old (possibly worn) coating on the mirror?

    Don't even know if this is possible, but I can't think of anything else that would cease to be an issue by simply covering the VF.
    Last edited by Jim Taylor; 10-02-2013 at 10:05 AM. Click to view previous post history.
    Cheers,

    Jim.

  8. #8
    smieglitz's Avatar
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    Quote Originally Posted by jimbop View Post
    I had this problem once - similar situation, high contrast night shots (of St. Peter's Basilica and the Vatican, if anyone's interested!!). It turned out to be internal reflections from within the camera - presumably stray light reflecting around inside the pentaprism.

    All I did to rectify was make shire that I used the eyepiece cover - I guess that was enough to reduce the reflections from the viewfinder eyepiece.
    I'll have her try this again while covering the eyepiece.

    But still, if the mirror flips up and blocks the imaging light from hitting the viewfinder/pentaprism during normal exposure, why would blocking the viewfinder from the rear affect an internal reflection, especially one originating from the front of the camera)? I can understand how it might affect the meter reading depending on where the cell was located, but the image? The secondary image does not appear smeared or distorted in any way which I would assume would happen if the mirror was somehow refracting the image. Also, why would a night exposure present this problem when daylight exposures do not exhibit it? I would again assume a daylight image would have a general fog or show the brightest areas in a scene (specular reflections, etc.,) also copied from the viewfinder/pentaprism if that was the source.

    I have seen pressure plate dimpled patterns reflected and imaged over an exposure (especially with HIE infrared and Olympus OM cameras) but if that was the source, the secondary image would not be inverted relative to the normal one. Ditto if the mirror was acting as a pellicle mirror. (Which BTW was originally introduced into 35mm cameras by Canon and only followed/copied later by Nikon after an 11-year lapse.)

    The problem remains (if you will excuse the pun) baffling.

  9. #9
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    If it were a reflection, wouldn't the image be reversed, not simply inverted?
    A prism may not reverse the image, but I'd think it would be difficult to reflect an whole image in this manner while the mirror is moving - I'd expect more of a light-leak from the area, not a full ghost image, unless there are a number of reflections occurring to produce this. Just guessing.
    Truzi

  10. #10

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    What lens is the student using? Filters, etc? Could they be photographing through a window? Very wierd.

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