Any way to avoid rainbowing through a condenser lens?

Discussion in 'Photography' started by Doc, Dec 18, 2006.

  1. Doc

    Doc Guest

    Pardon if this ends up being a repeat - Google hiccuped when I
    submitted the first time, I waited several minutes and it still hasn't
    appeared so I'll try again.

    Projecting 8mm film through a 6.5" uncoated plano convex condenser
    lens, there's this light "rainbowing" that appears on the left side of
    the image, with the convex side facing to the right. A short example
    posted here:

    The file is about 5 megs.

    Admittedly it's subtle and only noticeable under circumstances such as
    shown - against a grayish background like in this example. However I
    can see it and wonder if there's any way to get rid of it? Why does
    this happen? And why from left to right like this? I also get a similar
    effect going through a smaller - 2.5" - achromatic lens.

    Thanks for all input.
    Doc, Dec 18, 2006
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  2. Doc

    Dave Schaack Guest

    Doc, I looked at the clip multiple times and could not see anything where
    you drew the arrows. What I did see is that the nominally gray background
    appeared to change color balance during the clip. It appears reddish to me
    at the beginning and bluish at the end.
    Dave Schaack, Dec 20, 2006
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  3. Doc

    Doc Guest

    I tried different codecs to find one that had the most clarity within
    the size limitations I'm working with. I'm on dialup and have a 10 meg
    limit on my ISP's freebie website. Of course, it is subtle, and the
    monitor I'm using may be brighter than the one you're on - one of the
    reasons I like it, it's got great color.

    The tips of the arrovs follow the curvature of the outside of the
    rainbow. It's most readily visible in the portion when panning between
    the two fountain towers.
    Doc, Dec 21, 2006
  4. Doc

    Dave Schaack Guest

    I looked again, still cannot see it. I also suspect that my monitor is not
    as good as yours.
    Dave Schaack, Dec 21, 2006
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