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OT Help with Hot Pixels

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  • Felipe González
    Hi everyone I recently updated my Pano equipment and bought my first DSLR (a Canon Rebel XT with a Peleng 8mm). Last week I was shooting a night pano on a
    Message 1 of 4 , Nov 26, 2006
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      Hi everyone

      I recently updated my Pano equipment and bought my first DSLR (a Canon
      Rebel XT with a Peleng 8mm).

      Last week I was shooting a night pano on a restaurant and I noticed a
      few white and a nasty magenta pixel. My exposure was of 2 seconds.
      I guess the CMOS has "hot pixels" since all my pictures had exactly
      the same pixels in the same position. Afterwards, back in my studio, I
      made some test shots and this pixels appear starting at half second
      exposures and worsen as the exposure time increases.

      I read that "hot pixels" are inevitable, but I'd rather ask (I'm not
      even sure that this white pixels are hot pixels). Is there a method
      (other than cloning the adjacent information in PS) to avoid having
      this problem? Is it normal to have hot pixels or do I have to take my
      camera to service (it's still in warranty)?

      Any advice would be greatly appreciated.

      Thanks from the subtropical regions of Mexico

      Felipe B.
    • Rik Littlefield
      ... Felipe, Those sure sound like hot pixels . My old Canon 300D has 1-1/2 of them (one hot, one warm). Mine have never been troublesome enough to deal
      Message 2 of 4 , Nov 26, 2006
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        --- In PanoToolsNG@yahoogroups.com, Felipe González <felipe@...>
        wrote:
        >
        > Hi everyone
        >
        > I recently updated my Pano equipment and bought my first DSLR
        > (a Canon Rebel XT with a Peleng 8mm).
        >
        > Last week I was shooting a night pano on a restaurant and
        > I noticed a few white and a nasty magenta pixel. My exposure
        > was of 2 seconds. I guess the CMOS has "hot pixels" since
        > all my pictures had exactly the same pixels in the same
        > position. Afterwards, back in my studio, I made some
        > test shots and this pixels appear starting at half second
        > exposures and worsen as the exposure time increases.
        >
        > I read that "hot pixels" are inevitable, but I'd rather
        > ask (I'm not even sure that this white pixels are hot
        > pixels). Is there a method (other than cloning the adjacent
        > information in PS) to avoid having this problem? Is it normal
        > to have hot pixels or do I have to take my camera to service
        > (it's still in warranty)?
        >
        > Any advice would be greatly appreciated.

        Felipe,

        Those sure sound like "hot pixels". My old Canon 300D has 1-1/2 of
        them (one hot, one warm). Mine have never been troublesome enough to
        deal with. But it sounds like you have several more, which strikes
        me as quite a few. I recommend trying to get it fixed as a warranty
        repair. Test/demonstrate under the nastiest conditions that make
        sense for your work, then make sure that the service people
        understand that the problem really is interfering with your use of
        their otherwise excellent camera.

        --Rik
      • Tim Hatch
        ... I found a page [1] that says Custom Function #2 ( Long Exposure Noise Reduction) takes a dark frame of the same length as your long exposure and subtracts
        Message 3 of 4 , Nov 26, 2006
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          >> Last week I was shooting a night pano on a restaurant and
          >> I noticed a few white and a nasty magenta pixel. My exposure
          >> was of 2 seconds.

          I found a page [1] that says Custom Function #2 ("Long Exposure Noise
          Reduction) takes a dark frame of the same length as your long
          exposure and subtracts it automatically on the 5D and 20D. A quick
          test on my 350D reveals the same behavior – that the "busy..." after
          taking an exposure does indeed last as long as the exposure with
          C.Fn#2 enabled, but is nearly instantaneous otherwise. My tests were
          with a 30sec exposure, I'm not sure when C.Fn#2 kicks in.

          Tim

          [1]: http://www.dpchallenge.com/forum.php?
          action=read&FORUM_THREAD_ID=486252
        • John Riley
          I don t know if this would work the same for a Canon, but with my Fuji S2 the hot pixels get mapped out in the RAW conversion. Hot pixels are there if I shoot
          Message 4 of 4 , Nov 26, 2006
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            I don't know if this would work the same for a Canon, but with my
            Fuji S2 the hot pixels get mapped out in the RAW conversion. Hot
            pixels are there if I shoot a long exposure in jpeg and are also
            there before the conversion when I shoot in RAW, but gone after
            conversion. Do a long exposure with the lens cap on in jpeg and RAW
            and compare the two after converting the RAW.

            Almost all sensors have some hot and/or dead pixels. The cost of the
            sensor would be much higher if the QA was such that _no_ dead pixels
            were allowed. On some cameras, you can remap the dead pixels so that
            they are eliminated in the camera. When I was still using a Nikon
            995, I used a program that made the camera do just that. Before,
            lots of hot pixels; after, none (at least not showing.) I don't know
            if you can do that with a DSLR.

            If you are in a hot region of Mexico, that would exacerbate the
            problem, as sensor noise is temperature sensitive.

            John

            John Riley
            johnriley@...
            jriley@...




            On Nov 26, 2006, at 7:13 PM, Felipe González wrote:

            > Hi everyone
            >
            > I recently updated my Pano equipment and bought my first DSLR (a Canon
            > Rebel XT with a Peleng 8mm).
            >
            > Last week I was shooting a night pano on a restaurant and I noticed a
            > few white and a nasty magenta pixel. My exposure was of 2 seconds.
            > I guess the CMOS has "hot pixels" since all my pictures had exactly
            > the same pixels in the same position. Afterwards, back in my studio, I
            > made some test shots and this pixels appear starting at half second
            > exposures and worsen as the exposure time increases.
            >
            > I read that "hot pixels" are inevitable, but I'd rather ask (I'm not
            > even sure that this white pixels are hot pixels). Is there a method
            > (other than cloning the adjacent information in PS) to avoid having
            > this problem? Is it normal to have hot pixels or do I have to take my
            > camera to service (it's still in warranty)?
            >
            > Any advice would be greatly appreciated.
            >
            > Thanks from the subtropical regions of Mexico
            >
            > Felipe B.
            >
            >
            >



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