Carl Zeiss Biometar 80mm on Nikon D300

Discussion in 'Nikon' started by avishek_aiyar, Aug 7, 2011.

  1. Hello,
    I recently acquired this lens (its the newer MC version and not the Zebra) from fleabay. I mounted it to my Nikon D300 using the Pentacon 6 to Nikon F adapter.
    However, while using it yesterday I noticed something really weird.
    Wide open and maybe upto f4 it is OK....but when stopped down further, it develops a weird white band in the middle of the picture.
    Pictures are here: http://www.flickr.com/photos/smiling_buddha/sets/72157627376964706/
    The first one is wide open and then the 2 shots are stopped down to f5.6 and all the way respectively.
    I ran tests with my Kiron 105mm and my 60mm macro Elmarit and I could not see the same effect. So, I think we can rule out the camera sensor being responsible for this.
    I would appreciate any insight any of you may have.
    Thanks a lot!
    Avi
     
  2. Interesting.
    It looks to me that the more you stop down the less contrast you get. And that is kind of backward. Does your adapter have a lens in it? Because it looks a little like internal flair and I would expect a Zeiss lens to not produce internal flair.
     
  3. Mike,
    Thanks. The P6-Nikon adapter is lenseless. The P6 register is much higher than the F mount FFD, so no need for optics in the adapter.
    Thanks.
    Avi
     
  4. Exposure does not seem consistent between the 3 photos, the second one (f/4) looks about 2/3EV brighter than the wide open one (which does not look very sharp, to be honest). The f/5.6 one, sure the white band is weird, but it's rather hard to judge what it could be (in my view), since the photo suffers from what looks like considerable camerashake.
    I can understand these are quick test-shots, but it would be wise to repeat as more controlled experiments (tripod, sufficient light).
     
  5. Second for adapter internal flare, a common problem with low cost adapter. I would look for shinny stuff just outside of the sensor light cone but with-in the lens image circle (ie: screw). Cover that up and your problem should go away.
     
  6. Wouter....you are spot on....these were quick hand held tests....I know the camera blur adds to the complexity, but I felt that the artifact was present irrespective. Anyways, I will conduct some detailed tests soon.
    Tommy...are you referring to reflections off the adapter itself? Hmm....I should look into it.
    Thanks!
    Avi
     
  7. Flare, somewhere. This certainly does not occur on the Biometar in its native P6 environment, nor have I seen it in the few times, I've mounted it to a Canon EOS camera.
    However, your post does remind me that I need to get a P6>Nikon adapter, too. The P6 Sonnar 180mm f/2.8 is one of the best I own in any mount.
     
  8. Hmm To me this looks like a reflection of the subject , reflected back by the sensor into the rear element of the lens, and back again towards the sensor. .
    It makes sence that this effect is stronger when closing down the aperture, like glass with a dark surface on the backside acting like a mirror..
     
  9. I think it is light bouncing around from the aperture iris. Is it shiny? I've had lenses where the light bounces off the front elements and back, and causes this. Most noticeably on longer exposures.
     
  10. Another +1 to internal reflection from inside the adapter. Stopping down increases the image circle of the lens (well, not strictly true, but near enough) allowing the outer part of the image circle to strike any reflective surface and bounce back strongly. It's important to stop these flare-causing reflections, especially with a lens that's been designed to cover a larger image circle than that of the camera it's being used on.
    Avishek. You need to look at the inside of the adapter and see if there are any areas not covered with matt black paint. But black paint itself is usually not enough to suppress flare, there should be ridges or baffles in a decent adapter or extension tube. If the tube hasn't been machined with ridges, then no amount of paint will properly stop internal reflections. There's only one material that'll do the job, and that's black velvet. Buy a piece of black velvet from a fabric supplier, cut it to size and double-sided tape it all over the inside surface of the adapter. If that doesn't solve the problem, then nothing will.
     
  11. Thanks so much to all. I will take a look at the adapter at the first opportunity and get back.
    Avi
     

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