70-200 VR bokeh question

Discussion in 'Lens Lust' started by Beezle, Jul 1, 2005.

  1. I use this lens quite often, and cannot really complain about the results.

    But now and again, I find that I get bokeh that exhibits a sort of doubling effect. I did some experimentation to see if I could determine what causes it.

    Light reflecting off of the filter? VR? Light? And I could not actually find any difference that accounts for it. It was actually difficult to reproduce, except for one case. I find that shooting through double pane glass can definitely make it worse unless shooting nearly perpedicular to the glass.

    Another thought I've had is if it might be focal length and/or focus distance related. Haven't tested that out as yet.

    Example of what I see in regular use:

    [​IMG]

    Anyone have an ideas on how to control it? Avoid it? Nature of the beast?

    Thanks,

    Ed
     
  2. It'll happen whenever you have a high contrast object in your background. Just compose tight and avoid anything harsh and you'll be fine.
     
  3. Ed, I routinely see that with my 70-200VR. I've also found that it's noticeably worse when using a teleconverter as well. I haven't experimented much with different combinations of things to see what tends to accentuate it, but I've wondered if VR being turned on or off would make a difference. Have you tried that?

    One of these days I'll put some time into this to see what conditions make it worse. In the meantime, virtuamike's suggestion seems reasonable as a starting point.
     
  4. I might be wrong but I have determined it is the VR trying to *correct* what it sees as motion blur. I couldn't find any other logical reason. It only happens when the bokeh is *just* the right amount to appear as motion blur. Try this -- find a subject / distance / aperture that gives the effect with VR on. That's not as easy as it sounds because even though it may seem like it, it does not happen very often at all. Shoot the same scene with everything the same except with VR off. I'll give you odds the "doubling" is gone -- at least it was in my test. A strong, narrow vertical seems to produce it the easiest -- that is if you can figure out the correct distance/aperture. Took me several sessions to find the right combo.

    Phil
     
  5. JeffKohn

    JeffKohn

    Apr 21, 2005
    Houston, TX
    I've noticed it most when there are lines in the background (branches, grass, etc) that aren't completely blurred out. I think part of it is just a characteristic of the lens, it handles specular highlights very well but when it comes edges/lines it just doesn't fare as well.
     
  6. Thanks for the comments.

    Phil, I tried some shots with various sorts of detail out of focus with the idea that I would compare VR on and off as well as removing the Nikon filter I keep on the lens.

    I saw no difference between the above, then again I wasn't seeing the doubling effect at edges. This was indoors, which led me to think it could be a focus distance or focal length thing as well.

    I want to say it is like the areas that happens in are over OOF. If that makes any sense.

    Here is the resized full frame of the image that the above comes from. It might seem odd to shoot a basically landscape image using a 200mm zoom, but I really like how this sort of lens compresses such a scene.

    [​IMG]
     
  7. Makes perfect sense. The area has to be just the right amount of OOF (or, bokeh) for the effect to appear -- not too little, not too much. There also needs to be stark contrast behind the object so the cam/lens can better "see" what seems to be motion blur but is in reality the right amount of OOF to confuse what VR is looking for to correct. The instance I finally found and was able to test was a flag pole against some distant, darker trees. The cam was at F2.8 and the focus point was a distance (don't remember what), the pole was about twice that distance or a little more and the background was far enough to be almost a total blur. Like I said, it took several tries before I found a repeatable set so I could test.

    Doesn't seem odd AT ALL to me. A 70/80-200 to 210 zoom has long been one of my faves for landscape shooting. It is *much* easier to compose and isolate a small section of the grand landscape than to sort the jumble in a WA. I would say the vast majority of my "landscape" shots have been in the 70 to 135 or so range with many at the full 200.

    Phil
     
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