Purple fringe sample from Sony DSC-F828

Discussion in 'Digital Photography' started by Richard J Kinch, Jun 7, 2004.

  1. Here's the first instance of purple fringing I've seen from my Sony DSC-
    F828:

    http://www.truetex.com/purple_fringe_sample_sony_dsc-f828.jpg

    [note: 490 KB JPEG file]

    Look at the mirrored trophies and you'll see obvious purple fringes
    around the specular reflections of the on-camera flash firing. Note
    that depending on where they are in the scene, the reflexes have varying
    degrees of fringing, down to none. The reflex off the glass in the
    distance also shows no fringing.

    This is a poor shot: mercury vapor overhead lighting, flash, the camera
    was pushed to ISO 400 speed (resulting in the noise and dithering), and
    a lot of smear from hand-holding a long exposure. So please don't take
    this as typical of the photos that this camera can produce. I like this
    camera and have yet to see this purple fringing problem in any of my
    normal scenes. I simply want to submit this as an example that people
    can use for analysis of the fringing problem.

    I had a notion that the fringing might be some kind of afterimaging,
    given the smearing of the entire image. But in looking closer the
    fringes seem to be symmetric.

    Note that the above link is to a 490 KB recompression of the original
    3.3 MB JPEG file from the camera, which must have introduced some
    additional compression artifacts. I can post the original if it should
    be important.

    Richard J Kinch
    http://www.truetex.com/
     
    Richard J Kinch, Jun 7, 2004
    #1
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  2. Richard J Kinch

    Vubast Guest

    I see a picture in poor ficus with camera movement. I don't see purple
    fringing, and I havcen't seen any in annything I've shot with my own F-828 so
    far.
    "Dan I Ain't"
     
    Vubast, Jun 7, 2004
    #2
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  3. It's there. Take a look at the trophy that's being held by the guy on
    the right. It's half purple in the highlight areas.

    Now... Nevermind the fact that the picture's out of focus... The guy
    on the right looks like he has a matte line around him, as if he was
    pasted into the picture from another one. Although I guess it could
    be a motion blurr...
     
    Paul Fedorenko, Jun 7, 2004
    #3
  4. Richard J Kinch

    vince Guest

    Purple Fringing (or chromatic aberrations) do not come from any image
    processing problem, but from the lens, that do not focus all colors
    exactly at the same point on the sensor). If you try to shoot photos
    with very high contrats (against the sun for example..), you are more
    likely to get some.

    After, I don't know really why, but 8Mpix Cameras seem to give more
    fringings than 5Mpix. It might also come from the size of the sensor.
    But do not worry, it is not a problem of your camera : all DSC828 do
    it!

    Vince
     
    vince, Jun 7, 2004
    #4
  5. The lens is in focus. The blur is a combination of camera shake on the
    long expopsure, subject movement, and the ISO 400 dithering.

    The matte-looking shadow I'm not sure about. It may be the flash shadow
    with movement. But the flash is above the lens, so the shadow should be
    below the subject. Hmmm.
     
    Richard J Kinch, Jun 9, 2004
    #5
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