ACK! Purple fringing, 85mm 1.8, D2x

Discussion in 'Lens Lust' started by ednaz, Jul 9, 2005.

  1. ACK! One of my favorite lenses has always been the 85 1.8 - light, sharp, crisp. Was shooting for a charity a couple days ago, and shot a family portrait with the 85 1.8 - the backgrounds were awful so I needed f1.8 to make them go away. Put me farther away from a foursome than I usually want to be, but it worked.

    Then I pulled it up on the screen, and there was fringing like I've never seen before with any lens. Used this lens for years with film and my F100s, and with my D100 since I got it. But on the D2x - well, see for yoru self. Example from a small piece of the image below.

    Anyone else have a problem with this lens and the D2X?

    I guess the closest thing to good news is that the 24-120VR is even better with the D2x than it is with the D100. Go figure.

    [​IMG]
     
  2. How would you fix that?

    Mike
     
  3. Very good question, Mike

    You can photoshop it away, but it's tedious work. (Trust me I know, because I did it...) Even the lens fringing adjustments in Adobe RAW wouldn't handle it.
     
  4. ckdamascus

    ckdamascus

    928
    May 14, 2005
    New Jersey
    This is not surprisign to me at all. I was under the impression the 85mm f/1.8 was highly susceptible to this due to lack of ED elements.

    http://www.camerahobby.com/Review-70-200mmVR.htm

    Scroll down to see the comparisons of the 85mm, 80-200mm, and 70-200mm VR with purple fringing on the pole.

    The 85mm prime loses to the zooms. No big surprise there since there is not any ED elements in that prime.

    As to how to fix it, you can usually reduce it by modifying the saturation of the purple.

    Under Photoshop

    Go to Hue/Saturation
    Use the pen to pick the purple OR just pick magenta as a starting point.
    put -75 for saturation and -17 for lightness.

    Keep picking the purple spots and hope it does not clobber the rest of the image. Or, slide the color bar until it seems to 'find' the purple. It should dull the purple out significantly.

    Of course, this does not always work unerringly and it can be quite a pain in the butt.
     
  5. CK, that's what I had to do

    Pain in the butt is way underplaying the problem, frankly. I ended up doing similar to what you said on a layer, and basically editing pixel at a time. UGH. But, I shot about 15 shots - with four people in the picture, you need about 4x the number of people shots to guarantee one where no one has a goofy expression, or at least that's my rule of thumb - and this one was the only one that met that criteria.

    I"ve never had fringing with the 85 before, even shooting wide open in all kinds of conditions. On the other hand, I'd never used it on the D2x. I think I might have learned something about the angles of the light out the back of this lens vs the sensor; that's been my theory as to why the 24-120VR is so much better on digital than on film, the light out the back is at better angles to the sensor, where film doesn't matter.

    I really don't want to have to buy the 85 1.4, I don't need another two-ton lens. Sigh.
     
  6. Chris101

    Chris101

    Feb 2, 2005
    Arizona
    My Quick and Dirty...

    [​IMG]

    Go into Quickmask and Fill the entire picture.
    Select an eraser brush just the width of the purple line.
    Erase the purple line from the mask.
    Go back to normal mode, the purple line is now selected.
    Go to Hue/Saturation.
    Select Magenta, then expand the color selection with the dropper. Over do it.
    Desaturate the selection somewhat, and change the hue/lightness to closely approximate the color of the surrounding skin.
    You are done.

    It's not perfect, but it won't be anywhere near as noticeable.

    PS, Hey, is it just me, or are tatooed mamas hot?
     
  7. JeffKohn

    JeffKohn

    Apr 21, 2005
    Houston, TX
    If you shoot RAW CA can be corrected in either ACR or the latest version of NC. The correction in ACR seems to work fairly well and is a lot easier than any manual process I've tried. CS2 also has the lens correction tool but I don't know if the correction works as well there as it does in ACR.
     
  8. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    This does not look as CA to me, more like demosaicing artifact. Was it NEF?
     
  9. NEF it was

    And, I tried converting it with ACR, Capture, and RawShooter, and it's there in all of them - I wondered if it was the conversion myself, but figured if it was there in all three conversions, it was probably some interaction between the lens and the sensor.

    My first thought wasn't even fringing. It was such a hideously hot and humid day that you could see the humidity in the air, and I figured I was getting something related to that since the 85 has been such a reliable "go to" lens for me.
     
  10. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    It would be very interesting to see if this fringing is in the NEF itself
     
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