Advice on purple fringing

Discussion in 'Digital Photography' started by Stoneman, Oct 11, 2007.

  1. Stoneman

    Stoneman Guest

    I'm a photography noob so try not to flame my ass too much. :)

    I recently purchased a Fuji S700 and noticed that when I take pictures
    in the shade, and the sky is really bright, the light from the trees
    above can show purple fringes in the extreme edges. I have a few
    questions on how to minimize this problem.

    - Would buying a UV or polarizing filter help cut down on the
    - Should I just use Photoshop and remove it using software?

    I got a super deal on the camera and I can live the the purple
    fringing. It only happens when there is a huge difference in the light
    balance between where I am taking the shot and the back ground.
    Compared to my old camera, this one should make it a few years.


    Stoneman, Oct 11, 2007
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  2. Stoneman

    Scott W Guest

    I had, well still do have, a Sony F828 which also has a lot of purple
    fringing. Most of the time I just left it in the photo, people rarely
    notice it in a print. When I wanted to get rid of it I would selected
    and de-saturate it with maybe just a bit of darkening.

    I never had luck with UV filters, a polarizing filter might help a bit
    in that it will sometime darken the sky. Note that it has to be a clear
    day and the sun has to be at the right angle to get much benefit from this.

    Scott W, Oct 11, 2007
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  3. Stoneman

    Rich Guest

    The purple fringe you see isn't really just fringe. The purple colour
    is diffused across the whole image. It is the defocused blue and red
    light cause by the lens not being able bring all colours to a single
    focus point. You can use PS or PSP, whatever and remove the purple
    glow as long as it isn't too bad or doesn't bleed directly into the
    object it surrounds. If you are forced to remove a lot of it, you can
    see all the image's colour change. The net result of the light being
    diffused across the whole image is a reduction in image contrast.
    Rich, Oct 11, 2007
  4. Stoneman

    Stoneman Guest

    Thanks for the responses everyone. I am going to experiment a bit with
    the camera and maybe get a filter or two. The filter will also help me
    protect the lens when the camera is in use.

    Stoneman, Oct 11, 2007
  5. Stoneman

    Ray Fischer Guest

    Good question, though.

    The fringing is inherent in the lens. It comes from lenses acting
    sort of like prisms and separating out the colors of light. Even
    expensive lenses can show it.
    Ray Fischer, Oct 12, 2007
  6. Stoneman

    Alex Monro Guest

    This is a common problem with many digital cameras, fundamentally down
    to the design of the lens and sensor. It's due to the angle that the
    light from the lens strikes the sensor - at less than straight on the
    microlenses don't pass the same amount of light to each of the red,
    green & blue photosites in the Bayer array of the sensor.

    This is different to chromatic aberation, which is when the lens
    focusses different colours in slightly different places.
    That's one way, though it can get tedious.

    Although I find purple fringing is a problem with my Fuji S9500 at wide
    angle (28mm equiv), the problem goes away when I zoom in slightly, and
    at 50mm equiv it's unnoticeable even at 100%. The changing optical
    path as I zoom in results in the light striking the sensor more straight
    on. You might try zooming in a little, and stepping back.
    I find that tree branches against the sky are the biggest problem.
    Alex Monro, Oct 12, 2007
  7. Stoneman

    HEMI-Powered Guest

    Rich added these comments in the current discussion du jour ...
    I've always thought, rightly or wrongly, that much of the color
    fringing is chromatic aberration from the lens. I more often see
    a turquoise color in my Rebel XT images rather than purple. PSP,
    beginning with 9, has had a CA removal filter but I have found it
    both problematical to use and relatively ineffective. When it is
    really bad, I use a PSP 9 tool called Change To Target Brush to
    mildly change the fringing to a grayer, less objectionable color.
    HEMI-Powered, Oct 12, 2007
  8. Stoneman

    HEMI-Powered Guest

    Alex Monro added these comments in the current discussion du
    jour ...

    I didn't know that fringing in this context is different than
    classical CA, which I just commented on in another reply.
    Interesting idea no matter what causes it.

    HEMI-Powered, Oct 12, 2007
  9. Am I seeing this effect on my Canon 30D using the 24-105 f/4L
    at absolute closest focus distance, at 105mm? There is certainly
    something blurry and blue going on at edges near the corners.

    It does not appear focused at reasonable (non-macro) distances.

    It is correctable to some extent in software.

    Doug McDonald
    Doug McDonald, Oct 12, 2007
  10. Do a Google search. You can find step by step instructions.
    Ockham's Razor, Oct 12, 2007
  11. Ockham's Razor, Oct 12, 2007
  12. Stoneman

    KGB Guest


    Like you, I am not an expert - I haven't a clue about the technical
    side of photography and have just about figured which bit of the
    camera to point at an object; but like you I wanted some way of
    getting rid of the purple bits from my holiday snaps.

    I use the following, which I found on the WWW and saved as a doc file
    - I forget the original URL so have copied the doc file here. It
    works fine for me and is fairly straightforward, certainly not as
    complicated as it sounds; and as long as you don't actually save the
    result until you are happy, you are not going to cock up your original
    shot - or safer still save it as a copy.
    Step 1
    Open your image in Photoshop.
    once opened go to image > mode and you will see a list of possible
    mode changes that can be selected. For this operation we want to
    choose 'Lab Colour'. Changing to Lab colour in Photoshop is a
    non-destructive mode change so there is no need to worry about loss of
    image quality.

    Step 2
    Once converted to Lab colour you will notice on the channels palette
    that we now have three different channels than what we previously had.
    Before we had red, green and blue and now we have Lightness, A and B.
    To carry out this operation we shall be using channels A and B, these
    channels hold the colour information in the image.
    Select 'channel A' from from the channel palette, you will notice this
    is a very different image than what you opened up. Select filter >
    blur > gaussian blur from the menu at the top. Now you have the
    gaussian blur tool enabled move the slider to the right to add more
    blur. What is in effect happening is that you are softening the colour
    information in the selected channel. A good place to start is to
    remove the sharp edges in the channel and click ok and see what your
    image looks like with all the channels selected, so click ok and
    select Lab again. You will see the red fringing on your image has
    decreased slightly.
    Now do the same procedure with channel B and remove the sharp edges in
    that colour channel, click ok then review your image by selecting Lab
    again with both channels now slightly blurred. You will see this has
    significantly removed the fringing from the edges in the image.

    Every image is going to be different in the amount of colour fringing
    so just experiment here by adding more blur or if you feel you added
    too much to start with just go back using history and retry again.
    Remember not to overly blur any of the channels as by doing this you
    are removing the colour information from the image.

    Step 3
    If the saturation in the image has decreased a little by doing this
    then now is the time to add a bit of saturation to the image,
    remembering not to over do it.

    Step 4
    Once you are happy with the outcome just convert your image back to
    RGB using the image > mode route and save your image to its original
    format once again

    I have also used PFree0.2 with good results - URL is
    <> and it is freeware.

    Whilst they both work, of the two methods - the first (changing to lab
    mode in Photoshop) - seems the most effective.


    KGB, Oct 13, 2007
  13. What a joke! This actually removes the color from you photos ...
    not just the fringing, but ANY area of that color! And since
    the usual main subjects of my photos afflicted with the blue/purple
    fringe problem are flowers, frequently this would remove color
    from the main subject (assuming of course the procedure was applied
    to the whole image.)

    What I meant by correctable in software was by using the
    procedure used for fixing lateral chromatic aberration, that is,
    rescaling of the size of the three color images.

    Doug McDonald
    Doug McDonald, Oct 13, 2007
  14. Stoneman

    Ron Hunter Guest

    Then there is the rather more obvious, if more expensive, approach of
    buying a camera with sensor and lens system that doesn't HAVE the
    problem... Something to put on one's 'essentials' list for next purchase.
    Ron Hunter, Oct 13, 2007
  15. Ron Hunter wrote:

    An even easier solution is to use one of the other lenses I own.

    The problem with that is carrying all this stuff around. The lens
    with the "problem" is my best "walk around" lens, for most purposes.
    Focused at farther than say three feet it is superb. There really
    isn't a better lens! I was just looking at the pictures in question.
    They are lovely pictures. But ... I didn't have the other lenses with
    me, and thankfully so. These pictures were made on the summit of Mt.
    Elbert, at 14,400 feet ... and I got there just in time for the
    thunderstorms to start up in the distance. I would have been later
    if I had carried all the lenses I own, "just in case", rather then
    just the general purpose one. I own quite a heavy collection! Better
    use the weight for a tripod (which I didn't carry anyway ... too heavy.)
    The lens I brought made a fabulous 360 degree panorama.

    Would you like to recommend a lens for the 30D that both covers
    the wide to medium tele range, is relatively fast, and makes
    BOTH distant shots and modest macro shots that are better than
    the 24-105 f/4L IS? And, oh yes, it has to be IS.

    Doug McDonald
    Doug McDonald, Oct 13, 2007
  16. Stoneman

    Jim Guest

    And I thought that chromatic abberation that is severe enough to be seen was
    banished years ago.
    Jim, Oct 14, 2007
  17. Stoneman

    I Guest

    Does your camera come with software for uploading you images to the
    computer? If so, maybe the software can reduce the CA (purple fringing). I
    shoot Nikon DSLR and use Nikon's software to all but eliminate the fringing
    from the lesser quality lenses.
    I, Oct 14, 2007
  18. Stoneman

    irwell Guest

    The latest version of Irfanview includes a very good
    CA correction in the Effects Folder.
    irwell, Oct 22, 2007
  19. Ockham's Razor, Oct 22, 2007
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