What is acceptable number of dead and/or hot pixels?

Discussion in 'Digital Photography' started by PeterH, Apr 26, 2004.

  1. PeterH

    PeterH Guest

    I have a Canon 300D and have carried out the following pixel check.

    Set lens to manual focus

    Set camera to manual, aperture to 4.5, shutter speed to 30 seconds.

    Left lens cover on and also covered viewfinder.

    Took one shot in RAW mode and converted to tiff file.

    Tested for dead and hot pixels using DeadPixelTest software.

    Results are 0 dead pixels and 5 hot pixels (pixel area is X=2917 to 2919 and
    Y=1363 to 1365).

    Is this result acceptable?

    What would the range of dead and hot pixels be before taking the camera back
    to the manufacturer?

    regards

    PeterH
     
    PeterH, Apr 26, 2004
    #1
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  2. PeterH

    PeterH Guest

    A bit more info.

    The previous result of 5 hot pixels was taken at ISO200.

    Re-tested at ISO 1600 at 30secs and f4.5 and got 0 dead and 46 hot pixels.

    PeterH
     
    PeterH, Apr 26, 2004
    #2
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  3. PeterH

    Jim Townsend Guest

    Pretty well all digital cameras have some stuck or dead pixels. The acceptable
    amount is pretty well up to you to decide since you will be using the camera.

    If you take a lot of 30 second pictures with the lens cap on, then you might
    have a concern. However, if your real life pictures are coming out OK, then
    I wouldn't worry about it :)
     
    Jim Townsend, Apr 26, 2004
    #3
  4. PeterH

    BG250 Guest

    Yes. You only have one hot pixel really. The neighboring four show because
    of the algorithms that blend adjacent pixel levels (necessary on Bayer
    sensor cameras).
    Hot pixels are a fact of digital photography. There would be many more
    showing on the Rebel, but it has a built in algorithm to suppress most of
    them. My compact camera has 100 or so hot pixels that show at longest
    exposure. It looks like a color star field : ) Only a couple show under
    medium long exposure and it looks perfect under normal shooting.

    Dead pixels are another problem. I'd return or have the camera fixed if it
    had any.
    bg
     
    BG250, Apr 26, 2004
    #4
  5. PeterH

    Shaun Lowe Guest

    With lengthy exposures & higher iso values, hot pixels are a fact
    of life with all of the Dslr's out there. Stuck pixels are another
    matter all together & you shouldn't have any problems with that
    for a few years... hopefully, anyway.

    A few hot pixels here & there are easily cloned out.

    Regards,

    Shaun Lowe

    http://www.pbase.com/shaun
     
    Shaun Lowe, Apr 26, 2004
    #5
  6. PeterH

    Bill Hilton Guest

    From: "PeterH" replyto
    I bought a Canon 1Ds a month or so ago. The manual sez "There may be a few
    dead pixels ...They number no more than 0.02 percent (standard tolerance) of
    all effective pixels"

    So with your 6 Mpix Rebel could have up to 1200 pixels before Canon considers
    it out of spec, assuming this "standard tolerance" is what the industry uses
    (and if I did the math right).

    Bill
     
    Bill Hilton, Apr 26, 2004
    #6
  7. It wouldn't and wasn't acceptable for me.
    Got a replacement 10D w/o any dead/hot pixels and I'm happy now.
    I found the hot pixels when taking shots of a moonrise.
    Just have a look at the photo taken with the lens cap on. If you see the
    hot pixels, send the rebel back and ask for a new one.

    Cheers
     
    Gerhard Beulke, Apr 26, 2004
    #7
  8. Is this for the sensor or the LCD? Usually, such specs are for the
    acceptable flaw rate for the LCD.
    On the other hand, if it applies to a LCD display of approximatly 100000
    pixels, the limit is 20 dead pixels.

    Dave
     
    Dave Martindale, Apr 26, 2004
    #8
  9. PeterH

    Bill Hilton Guest

    I went back and looked again and you're right Dave, it's for the LCD. I didn't
    see an allowable % for the sensor.

    My duh, I really screwed THAT up :)

    Bill
     
    Bill Hilton, Apr 26, 2004
    #9

  10. Note that in the sensor manufacturing process, it is impossible to
    cost-effectively ship sensors with NO dead or hot pixels, but before the
    camera is shipped, those bad pixels are mapped out in firmware in each
    individual camera. One wouldn't know how many NATIVELY bad pixels there are
    on the sensor since they've been mapped out. If the OP has bad pixels when
    the camera came right out of the box, then it means most probably that the
    mapping process at the time of manufacture was substandard. The camera can
    be returned under warranty to re-map them out.

    If the camera re-seller or manufacturer will take it back to exchange for a
    new one, the go for it. But be aware that they may just want to send it back
    to the manufacturer for re-mapping, which is the standard way of dealing
    with such a problem.

    HMc
     
    Howard McCollister, Apr 26, 2004
    #10
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