What's with the obession with "Purple Fringing"?

Discussion in 'Digital Photography' started by Richard Dock, Jul 22, 2003.

  1. Richard Dock

    Richard Dock Guest

    What is with these geeks whining over and over about "purple fringing"?

    As a photographer with well over 30 years of shooting in 35mm, medium
    format, and large format B&W and color film and now digital (G3, D100), I
    can probably count on one hand the number of times I've ever tried or needed
    to take a picture of an indoor lighted scene with tungsten/flood/fluorescent
    lights like those shown in the dreaded "purple fringing" test shots.

    This is like saying you wouldn't sleep with Cindy Crawford because of that

    Get a life!
    Richard Dock, Jul 22, 2003
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  2. Totatally agree with you - seems to me there are two classes of camera user:

    Those of us who take pictures and enjoy our hobby/profession

    Those of us who keep up to date with the latest cameras and shoot nothing
    but test charts and test pictures - sad!
    UpForFunToday, Jul 22, 2003
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  3. Richard Dock

    Rick Guest

    I don't think that's a fair criticism. Chromatic aberration IS a problem,
    especially with high contrast outdoor shots. Canon and other camera
    manufacturers have spent years developing lens systems to minimize
    the problem.

    Rick, Jul 22, 2003
  4. While it can be taken too far, it is fair to expect the G5 to at least
    equal the performance of the G3, which sells for significantly less $$.
    Even with the resolution change it appears to be a much better value.
    Jason O'Rourke, Jul 22, 2003
  5. You started this totally unneccessary thread - so maybe you
    shall get a life. And me also for reading this :)

    Have a nice day and don't get all that upset over things.

    Roland Karlsson, Jul 22, 2003
  6. Richard Dock

    colinco Guest

    Isn't it more a function of the CCD??
    colinco, Jul 22, 2003
  7. Richard Dock

    Rick Guest

    Rick, Jul 22, 2003
  8. Richard Dock

    Ron Hunter Guest

    I agree. I have seen some shots where the problem made the picture look
    more like Roseanne Barr than Cindy Crawford.
    Ron Hunter, Jul 22, 2003
  9. Richard Dock

    Bernard Hill Guest

    Agreed. I have returned from holiday with 700 pictures from a mixture of
    cameras: Oly E10, Canon A20, Dimage Xi.

    The trees against sky in the Xi pictures show purple fringing, none of
    the others do. I find it a little off-putting.

    Bernard Hill
    Selkirk, Scotland
    Bernard Hill, Jul 22, 2003
  10. Richard Dock

    Terry Guest

    The problem does seem to occur only in very specific situations such as
    photographing lights which have a very dark background, so it may be that it
    is a problem with the CCD not the lens. I have not taken photos in these
    situations so I have not experienced it yet. There seems to be an obsession
    with Canon products regarding this problem on this NG. dcpreview showed
    this to have at least if not greater occurrence with the Oly C5050, which
    seems to always get favorable comments.
    Terry, Jul 22, 2003
  11. SNIP
    Very distracting indeed!

    Bart van der Wolf, Jul 22, 2003
  12. Richard Dock

    MA Guest

    See how this boat shot was spoiled:
    Are there any tricks you can use to get rid of this problem? What I am
    aiming at is filters or effects using an image processing application.
    It can't be very hard to automatically identify where in the picture the
    problem is most visible; what is best done to reduce it I don't know.

    Best regards, Magnus - who is a bit interested in automatic image
    MA, Jul 22, 2003
  13. Richard Dock

    philw Guest

    [...] dcpreview showed this to have at least if not greater
    Perhaps that just indicates that those with the machine you mention
    are less fussy about the quality of their images? If I had a quid for
    every time someone tells me that [insert name of consumer photographic
    gadget here] takes brilliant pictures then I could afford a second
    1Ds, which only takes brilliant pictures if you know how to drive it.

    Many of Canon's lenses exhibit chromatic abberations, although the L
    glass is generally pretty good. If you're using a partial-frame camera
    or looking at pictures on a consumer monitor you might not notice. My
    24-70L has a little CA when wide open at 24mm full frame. The 28-135
    is notocably worse at 28mm, as might be expected from a consumer lens.
    It's possible to correct most of this with Pano Tools. This type of CA
    is a lens design issue as per the DPreview link published above.

    A different problem is sometimes called "blooming". This happens with
    Bayer sensors when one or more channels are over exposed. The original
    post in this thread seems to be refering to this.
    Of course most of us haven't been working with digital for thirty
    years, but I have come across precisely this type of problem several
    times in the wild. I've had blooming both outside and indoors (tv
    studio). Once you know what it is, it's generally fixable and often
    philw, Jul 22, 2003
  14. Richard Dock

    Jim Townsend Guest

    Other than not shooting high contrast objects.. There isn't much you can do on
    the camera end.

    If the sun would have been at another angle, it wouldn't have been reflecting
    off the aluminum trim on the boat and the purple fringe wouldn't have

    Despite the fact that this lens exhibits the trait, it doesn't do it all the
    time... just when conditions are right.

    With an application like photoshop, it is possible to select the purple color
    and change it into something neutral (like grey) so it isn't as apparent.
    I've never done this, but I've read about it.
    Jim Townsend, Jul 22, 2003
  15. Richard Dock

    George Kerby Guest

    Your talking about mixed lighting shadowing, not chromatic aberration
    (purple fringing). Apples n' oranges.

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    George Kerby, Jul 22, 2003
  16. Richard Dock

    BG250 Guest

    I find it to be a BIG problem. If any of my film lenses did this, they'd be
    history. It is just unacceptable in some shots to have that false coloration
    showing. Using 35mm lenses on 35mm SLRs, I've never seen the problem show as
    bad as some of these digital cameras - even with consumer zooms.

    I hear someone has made Photoshop filters to clear the fringing problem near
    the edges.

    BG250, Jul 22, 2003
  17. Richard Dock

    Paul H. Guest

    I think "spoiled" is going a bit overboard, if you'll pardon the pun. You
    could have shown this picture to a thousand people and maybe _one_ of them
    might have mentioned the relatively minor fringing which appears along the
    highly reflective gunwale.

    Besides, your shot doesn't look at all like an example of chromatic
    aberration, but instead it looks like blooming distortion caused by electron
    spill-over from over-filled electron wells on the CCD. If it were chromatic
    aberration, there would be a spectrum of color represented: it would be too
    much of a coincidence for a lens system to be dispersive and at the same
    time absorb or reflect out all colors but the particular purple/magenta
    color in question.

    It should be possible to distinguish true chromatic aberration from blooming
    by using a procedure similar to this: Set up a test scene consisting of a
    sharp-edged object against a bright background, expose for the object and
    then take a series of photographs, keeping the aperture constant but
    decreasing the exposure by 1/3 EV for each successive photo. If fringing is
    due to chromatic aberration, the observed fringe should become _gradually_
    fainter as exposure declines, but if fringing is caused by blooming, a
    definite threshold effect will be observed, i.e., a particular exposure will
    be made at which fringing all but disappears, even though it was evident in
    all previous pictures.

    "Purple haze are in my brain,
    Lately things, they don't seem the same
    Acting funny, but I don't know why
    'Scuse me while I kiss the sky"

    --Jimi Hendrix, from the song "Purple Haze", on the over-reaction to the
    digital camera fringing problem.
    Paul H., Jul 22, 2003
  18. SNIP
    Using a smaller aperture usually helps some.

    Yes, that works (provided there are no subjects of similar color in the
    image, masking should be added to the cure then).

    Bart van der Wolf, Jul 22, 2003
  19. There are a bunch of different ways to clean it up in Photoshop. My
    favorite lately is the Healing Brush, set to color mode.
    Set the brush width a little wider than the purple fringe, option-click
    on something vaguely the right color, paint over the fringe, and it
    usually goes away nicely. If not, undo and try again.
    David Eppstein, Jul 23, 2003
  20. Richard Dock

    Paul H. Guest

    It is really easy to correct fringing in Photoshop Elements, Jim:

    1) Enlarge a section of the photo containing the fringe
    2) Use the eyedropper tool to select the distinctive fringe color
    3) From the main menu, select Enhance --> Color --> Replace Color
    4) Manipulate the "Fuzziness" slider until you've selected all the fringe
    5) Move the "Saturation" slider in the negative direction until you've made
    the fringe unnoticeable.

    Bingo--that's it! You _may_ have to do this a couple of times to eliminate
    the last vestige of "fringy-ness", if you're really picky. I actually did
    this to your boat photo and the result was quite good.

    It's funny--half the magic of Photoshop and its derivatives resides in
    selecting the correct mask.

    Paul H., Jul 23, 2003
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