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I shot a few rolls on Minolta XG-M with different lenses and some images have an underexposed edge. It take a while for me to go through a roll, to the point of me forgetting which lens/settings I used, but looking through the images, I'm fairly confident that

  1. The shaded region appears on the same side.
  2. It only appears when using my 70-210mm Vivitar.

That pretty much rules out shutter problems, I guess? Could it be the lack of a lens hood?

Here are some examples:

example 1 example 2 example 3

EDIT: Apologies for the mistake, the lens is Sigma Zoom-k II f/4.5 70-210mm Multi Coated Lens. Other lenses I use are Minolta MD 50mm f/1.7 and Minolta MD Zoom 24-35mm f/3.5, which don't seem to have this problem (from what I remember about the images taken). The zoom lens has some internal dust, but otherwise looks fine. Not sure how to test for thhe interaction between the aperture and a mirror. Also, I scan with a DSLR+zoom reverser, so had to improvise with these images, but the same shade doesn't seem to overlap with two frames:

requested example 1 requested example 2

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  • \$\begingroup\$ Have you checked the lens (and its aperture mechanism) for damage? Which Vivitar 70-210 anyway, there are at least 6 common versions made by different OEMs.... If there is nothing visibly wrong with the lens, the only explanation would be some foul interaction between the aperture control mechanics and the mirror system...... \$\endgroup\$
    – rackandboneman
    Commented Feb 12, 2019 at 15:19
  • \$\begingroup\$ Edited the question. The shadows seem to be localised to a single frame. The lens seems to work fine, not sure about it's interaction with the mirror though or how to test it. \$\endgroup\$
    – timberhill
    Commented Feb 12, 2019 at 20:14
  • \$\begingroup\$ @xiota I was thinking of a misbehaving aperture coupling making the mirror return too early (or the shutter operate too late)... \$\endgroup\$
    – rackandboneman
    Commented Feb 12, 2019 at 20:34
  • \$\begingroup\$ Have you tried reproducing the effect with the back open and the lens pointed somewhere bright and even? \$\endgroup\$
    – rackandboneman
    Commented Feb 12, 2019 at 20:42
  • \$\begingroup\$ Testing with the open back sounds good, I will try once the film is out. Thanks! \$\endgroup\$
    – timberhill
    Commented Feb 12, 2019 at 20:57

2 Answers 2

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It looks like light fall off from an obstruction, either in front of the lens or behind it. It's similar to, but too large to be, vignetting caused by diffraction of light along the edge of the film gate.

  • After seeing the frame edge, it doesn't appear to be caused by the film gate because the ocean picture shows the border of the film gate within the shadow.

    When caused by the film gate, it's usually pretty small and cropped off from printing or mounting, so you don't have to worry about it because it's not visible. If the pressure plate is loose or film gate deformed, it can be larger.

  • Some lenses have a frame behind the rear element. If the frame is not aligned with the film gate, it could cast a shadow on the film.

  • I doubt a problem with the aperture itself because that would affect the image globally, not along an edge. A problem, like a loose blade, would be visible in bokeh balls.

  • A shutter problem would have a sharper edge because it's pretty close to the film plane. They're also usually more obvious and variable. But this could be an early sign of impending shutter failure.

  • Could be poor mirror clearance if the shadow always occurs along the same edge. However, the mirror isn't supposed to move until after shutter is closed.

  • If the shadow occurs only when zoomed out, it could be related to imaging circle coverage, but I would expect the shape to be curved, like the imaging circle.

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  • \$\begingroup\$ That's interesting. Is that a thing that people have to deal with? Are you saying one should add some margin when taking a picture? \$\endgroup\$
    – timberhill
    Commented Feb 12, 2019 at 20:17
  • \$\begingroup\$ Ok, I will finish current film and check. How would one check it though? Apart from just looking at the pressure plate, mean. I assume the deformation, if it's there, would be quitw amall, right? \$\endgroup\$
    – timberhill
    Commented Feb 12, 2019 at 20:41
  • \$\begingroup\$ Also, why would it not show with shorter focal length lenses? I have SOME doubts about it, but can't find a definite example. \$\endgroup\$
    – timberhill
    Commented Feb 12, 2019 at 20:43
  • \$\begingroup\$ I don't think it's the pressure plate or film gate, but it doesn't hurt to check. No idea what the obstruction is, only that there's probably an obstruction. \$\endgroup\$
    – xiota
    Commented Feb 12, 2019 at 20:48
  • \$\begingroup\$ yeah, I will do, thanks. Most pictures I take with the zoom lens are fully zoomed in, because i would rather use the 50mm if I can get closer. Thanks for the hypotheses, I will try to check them out. Just got an XD7, so could see if it's the camera or the lens. \$\endgroup\$
    – timberhill
    Commented Feb 12, 2019 at 20:56
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It looks like you mirror may be blocking the edge of some of the shots.

Remember, the image is inverted in the camera and the bottom of the scene is projected onto the top of the film.

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