hot/dead pixels

Discussion in 'Digital SLR' started by bp, Jun 5, 2005.

  1. bp

    bp Guest

    What is "normal" as number of hot&dead pixels of a rebel XT's sensor?
    I've just noticed that I have a few in my camera and I don't know if I
    should send it for repairs.

    Thanks,
    Ogdan
     
    bp, Jun 5, 2005
    #1
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  2. bp

    Slack Guest

    I don't think there is a "normal" number. I, too, have a few/several on
    my XT. Bottom line is: It doesn't effect my pictures from what I've
    seen, so far. No need to send it in for "repair."
     
    Slack, Jun 5, 2005
    #2
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  3. Before you do anything drastic or expensive, try the freeware
    DeadPixelTest from http://www.starzen.com/imaging/utilities.htm and
    read the explanation. Dead pixels are relatively rare, but hot pixels
    are very common and show up primarily in longer exposures. My test found
    ten hots in exposures 1/4" and slower, visible when images were viewed at
    1:1 or larger.

    Fortunately, my Pentax *ist-DS has an optional post-exposure processing
    of long exposures to snuff out any hot pixels it finds. My 10 hot pixels
    appeared only while I had that option turned off.
     
    Charles Gillen, Jun 5, 2005
    #3
  4. bp

    Sheldon Guest

    My understanding is that a certain number of dead or hot pixels is normal,
    but the sensor is supposed to work around them. If they effect any of your
    photos you should get it fixed. I'm assuming you mean the image sensor and
    not the LCD display.
     
    Sheldon, Jun 5, 2005
    #4
  5. Hot/dead pixels are an inevitable consequence of digital imaging devices. If
    you don't have any now, you will later. Manufacturers evaluate each sensor
    to find hot/dead pixels at the time of manufacture and then program (re-map)
    so that the camera returns an average value of the pixels surrounding each
    bad one. You can do that yourself in post-processing with the clone-stamp
    tool (Photoshop), but at the point when it gets to be too annoying, you can
    always send the camera back to have it "re-mapped". Most camera
    manufacturers will do that for free while under warranty.

    HMc
     
    Howard McCollister, Jun 5, 2005
    #5
  6. The remapping function should be available to the user, IMO. Many cameras
    have this as a setup menu item, and providing it isn't too often, it's a
    real benefit compared to having to send the camera in for service.

    Nikon tend to hide this function away, but on some of their cameras it's a
    routine in the firmware which can be accessed with special commands.
    Users have even written programs to trigger the firmware routine. I've
    been grateful to these program authors on at least three occasions now!

    Cheers,
    David
     
    David J Taylor, Jun 5, 2005
    #6
  7. bp

    Stacey Guest

    And some actually have a remap feature in the menu so you don't have to
    send it anywhere...
     
    Stacey, Jun 5, 2005
    #7
  8. bp

    Trapezium Guest


    Olympus include pixel mapping on some of their cameras - it's an even
    better feature than their self cleaning DSLR sensor, but one that gets very
    little attention.

    FWIW, Sigma UK told me that their SD10 also has automated pixel mapping.

    'Hot' pixels that appear at long exposures are common, and can't be helped -
    but 'dead' pixels that show up in the same place at all exposure/speed
    combinations are the curse of digital photography and any camera exhibiting
    such a pixel should be returned under warranty (perhaps with a note pointing
    out that if the camera had a pixel mapping facility they wouldn't be
    receiving it back!)

    All the manufacturers could include pixel mapping a part of the camera
    firmware - but until customers start demanding that function they won't
    bother to implement it (possibly because they make money from running the
    same sort of software fix 'off camera')
     
    Trapezium, Jun 5, 2005
    #8
  9. bp

    RichA Guest

    Lets see what Canon charges if it's out of warranty.
    -Rich
     
    RichA, Jun 5, 2005
    #9
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