Uneven exposure

Discussion in 'Leica and Rangefinders' started by raul_zav, May 23, 2015.

  1. Dear friends,
    I shoot with leica M6, and recently came across an issue with the contax sonnar 90mm converted to M mount. The images have an over-exposed patch of uneven shape , usually at the top center (see photo). Does anyone encountered similar problems? The camera is not a problem, as with my 50mm and 135mm leica lenses I do not have this issue. Also I have my films developed at same place. I wonder whether this could be caused by loose parts in the lens, which may cause a slight angle between the image plane and the film surface.
    Thanks for your help!!
    Raul
    00dJ3Z-556889584.jpg
     
  2. All shots taken have this? What is the effect of a lens hood? The focus looks accurate. What about rectilinear subjects like
    buildings: are they straight? Looks like a major flare of light from reflective metal perhaps. Is everything tight with no
    wobble?
     
  3. Thanks for the reply.
    Straight lines and focus seem fine, and I do not use hood, which usually cause symmetrical problems. The barrel of the lens is indeed slightly wobbling
     
  4. It looks precisely like flare to me. What are the symmetrical problems that stop you using a lens hood? It is a round hood is it not?
     
  5. If it happens shooting with the light to your back and not into the light it must be a lens or mount problem. Do you have another camera
    to test it with?
     
  6. Ray: actually it DOES happen mostly with front/top light. What does it mean? I don't have another camera to test the lens.
    but since other lenses work fine, I thought the body is ok.
     
  7. James: I do not use hood, so I can't say if it will change anything in this case.
    by symmetry I meant vingetting
     
  8. Do you have the right hood? Lens manufacturers are fairly fastidious about supplying hoods which vignette. If it is the correct hood, can you fit a hood made for a 75mm or 50mm lens?
    From what you say, I would say the body is OK., It's just light bouncing around inside the lens, which would be normal if this was an uncoated lens, but it's modern, isn't it. Maybe the edges of the lens elements aren't blacked, & are picking up oblique light.
     
  9. As James says, and especially if you're shooting into the light, you should be using the proper hood. It's pretty
    common for lenses to flare when shooting toward a light source. Or, email DAG or Sherry Krauter with the
    image and ask them. They're both very helpful and will tell you what could be going on. You may want to
    send the lens in to have it checked and/or fixed if that's what they recommend.
     
  10. Many thanks for your help, guys! Seems like I'll get a proper hood firsthand and see if it helps
     
  11. There's always a bit more of a problem with RF Leicas than SLR's with flare, as SLR TTL viewfinder will at least hint if there is some flare, while with Leica, you can only anticipate flare.
     
  12. "The images have an over-exposed patch of uneven shape , usually at the top center "
    I wonder if flare would repeat itself in much the same way across a number of photos, all of them being taken with the same lens. I have been called fanatical about the use of hoods, but this problem does not look like it would be solved by one.
     
  13. In addition to everything stated about flare: also check for a light leak around the adapter/lens mount. This lens required
    some surgery to make into M-Mount.
     
  14. I will have the pictures taken with the original hood very soon. I will update on what I got later.
    thank you all!
     

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