EOS 10d, dead or hot pixel???

Discussion in 'Digital Photography' started by Mark N, Jul 22, 2003.

  1. Mark N

    Mark N Guest

    Hi troops,

    i have just taken some star trail pictures and upon examination, have
    noticed some pixels are unusually bright dont really belong in the image.

    I have heard about hot and dead pixels but dont know exactly what to look
    for.

    could someone take a look at these 2 images and let me know what the hell is
    going on here!!!

    http://www.marknowak.co.uk/images/pixel-1.jpg (17Kb)
    http://www.marknowak.co.uk/images/pixel-2.jpg (65Kb)


    There are a number of image 1 and 2 of image 2 in all of the images i have
    taken this evening. I have only noticed these when taking star trail pics,
    and so does not really affect the other types of photography i do


    Thanks for any help, Mark
     
    Mark N, Jul 22, 2003
    #1
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  2. Mark N

    Mark M Guest

    "Mark N" <> wrote in message
    news:pJ_Sa.2503$...
    > Hi troops,
    >
    > i have just taken some star trail pictures and upon examination, have
    > noticed some pixels are unusually bright dont really belong in the image.
    >
    > I have heard about hot and dead pixels but dont know exactly what to look
    > for.
    >
    > could someone take a look at these 2 images and let me know what the hell

    is
    > going on here!!!
    >
    > http://www.marknowak.co.uk/images/pixel-1.jpg (17Kb)
    > http://www.marknowak.co.uk/images/pixel-2.jpg (65Kb)


    Oh no!
    Yet another Mark! :)
    You've zoomed in on the image so much that it's hard to say.
    Post a simple full-res crop to give us a better idea.
     
    Mark M, Jul 22, 2003
    #2
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  3. Mark N

    Mark N Guest

    ok, i have posted a better image. its a 66% zoom into the image.

    http://www.marknowak.co.uk/images/pixel-3.jpg (59Kb)


    I have downloaded a small utility called deadpixeltest

    http://www.starzen.com/imaging/deadpixeltest.htm

    from this i realise that i have no dead pixels (phew) and seem to get more
    hot pixels the longer the exposure. I did a 30 second exposure test with
    this and it found no hot pixels until i dropped the threshold down to about
    30

    The longer the exposure, the more hot pixels. So i dont think that there is
    too much to worry about. Ahh, i can finally sit back, relax, and think about
    going to bed rather than staying up all night and trying to fix something
    that is not broken!!!


    Cheers :)




    "Mark M" <> wrote in message
    news:g8%Sa.13180$Bp2.335@fed1read07...
    >
    > "Mark N" <> wrote in message
    > news:pJ_Sa.2503$...
    > > Hi troops,
    > >
    > > i have just taken some star trail pictures and upon examination, have
    > > noticed some pixels are unusually bright dont really belong in the

    image.
    > >
    > > I have heard about hot and dead pixels but dont know exactly what to

    look
    > > for.
    > >
    > > could someone take a look at these 2 images and let me know what the

    hell
    > is
    > > going on here!!!
    > >
    > > http://www.marknowak.co.uk/images/pixel-1.jpg (17Kb)
    > > http://www.marknowak.co.uk/images/pixel-2.jpg (65Kb)

    >
    > Oh no!
    > Yet another Mark! :)
    > You've zoomed in on the image so much that it's hard to say.
    > Post a simple full-res crop to give us a better idea.
    >
    >
     
    Mark N, Jul 22, 2003
    #3
  4. Mark N

    ralford Guest

    presuming these are images of stars moving across the frame, what celestial
    body would have been stationary?

    Looks like a ccd issue to me. check the scale in Photoshop or similar and
    see if it is maxed out. ccd thermal noise (exposure dependant) should be
    "random", however, tests of exposure noise in my 5700 were repeatable. I
    actually had several hot pixels and the camera is in the shop for repair.

    good luck,

    rma



    "Mark N" <> wrote in message
    news:Ww%Sa.2526$...
    > ok, i have posted a better image. its a 66% zoom into the image.
    >
    > http://www.marknowak.co.uk/images/pixel-3.jpg (59Kb)
    >
    >
    > I have downloaded a small utility called deadpixeltest
    >
    > http://www.starzen.com/imaging/deadpixeltest.htm
    >
    > from this i realise that i have no dead pixels (phew) and seem to get more
    > hot pixels the longer the exposure. I did a 30 second exposure test with
    > this and it found no hot pixels until i dropped the threshold down to

    about
    > 30
    >
    > The longer the exposure, the more hot pixels. So i dont think that there

    is
    > too much to worry about. Ahh, i can finally sit back, relax, and think

    about
    > going to bed rather than staying up all night and trying to fix something
    > that is not broken!!!
    >
    >
    > Cheers :)
    >
    >
    >
    >
    > "Mark M" <> wrote in message
    > news:g8%Sa.13180$Bp2.335@fed1read07...
    > >
    > > "Mark N" <> wrote in message
    > > news:pJ_Sa.2503$...
    > > > Hi troops,
    > > >
    > > > i have just taken some star trail pictures and upon examination, have
    > > > noticed some pixels are unusually bright dont really belong in the

    > image.
    > > >
    > > > I have heard about hot and dead pixels but dont know exactly what to

    > look
    > > > for.
    > > >
    > > > could someone take a look at these 2 images and let me know what the

    > hell
    > > is
    > > > going on here!!!
    > > >
    > > > http://www.marknowak.co.uk/images/pixel-1.jpg (17Kb)
    > > > http://www.marknowak.co.uk/images/pixel-2.jpg (65Kb)

    > >
    > > Oh no!
    > > Yet another Mark! :)
    > > You've zoomed in on the image so much that it's hard to say.
    > > Post a simple full-res crop to give us a better idea.
    > >
    > >

    >
    >
     
    ralford, Jul 22, 2003
    #4
  5. Mark N

    Mark M Guest

    "ralford" <> wrote in message
    news:vj0Ta.82781$...
    > presuming these are images of stars moving across the frame, what

    celestial
    > body would have been stationary?


    You're kidding, right? :)
     
    Mark M, Jul 22, 2003
    #5
  6. Mark N

    Mark M Guest

    "Mark N" <> wrote in message
    news:Ww%Sa.2526$...
    > ok, i have posted a better image. its a 66% zoom into the image.
    >
    > http://www.marknowak.co.uk/images/pixel-3.jpg (59Kb)
    >
    >
    > I have downloaded a small utility called deadpixeltest
    >
    > http://www.starzen.com/imaging/deadpixeltest.htm
    >
    > from this i realise that i have no dead pixels (phew) and seem to get more
    > hot pixels the longer the exposure. I did a 30 second exposure test with
    > this and it found no hot pixels until i dropped the threshold down to

    about
    > 30
    >
    > The longer the exposure, the more hot pixels. So i dont think that there

    is
    > too much to worry about. Ahh, i can finally sit back, relax, and think

    about
    > going to bed rather than staying up all night and trying to fix something
    > that is not broken!!!


    I agree that nothing is broken.
    Actually, it's a pretty decent performance for a digital camera to only
    exhibit that one major flaw in long exposure.
     
    Mark M, Jul 22, 2003
    #6
  7. Mark N

    Jim Townsend Guest

    Mark N wrote:

    > from this i realise that i have no dead pixels (phew) and seem to get more
    > hot pixels the longer the exposure. I did a 30 second exposure test with
    > this and it found no hot pixels until i dropped the threshold down to about
    > 30
    >
    > The longer the exposure, the more hot pixels. So i dont think that there is
    > too much to worry about. Ahh, i can finally sit back, relax, and think about
    > going to bed rather than staying up all night and trying to fix something
    > that is not broken!!!


    I can't see your images tonight :( Your server must be down.

    Yes.. On the 10D, the longer the exposure, the more 'hot' pixels show up.

    I've found the acceptable limit is around 3 minutes.. Anything more, and you
    get lots of speckles..

    Below is a 600 second (10 minute) exposure I did last month. The speckles in
    the sky aren't stars.. (If they were, they'd be streaks). There are a couple
    of airplane light trails crossing the sky. The image is exactly as it came
    from the camera.. I copied it from the camera to my computer, then I copied it
    directly to pbase.com.

    (Caution this is a 2.5 meg download)

    http://www.pbase.com/image/19296218/original

    If you remove the '/original' from the end of the above URL, you'll see a
    smaller version of the image, but the speckles don't show up well on the
    resized versions.
     
    Jim Townsend, Jul 22, 2003
    #7
  8. Mark N

    Mark N Guest

    Indeed, i was actually very impressed with how low the noise is even with
    exposures as high as 5 minutes, there simply wasn't any significant noise
    (ISO set to 100).

    I live in a city and so 5 minutes is really the max exposure length - i
    found - before the image would be washed out by street lighting. But next
    time i go away somewhere remote id love to try 1 hour or more exposures ;-)

    Mark



    > I agree that nothing is broken.
    > Actually, it's a pretty decent performance for a digital camera to only
    > exhibit that one major flaw in long exposure.
    >
    >
     
    Mark N, Jul 22, 2003
    #8
  9. Mark N

    Mark M Guest

    "ralford" <> wrote in message
    news:pt9Ta.86160$...
    > not kidding at all. Polaris would appear stationary in a time exposure,
    > however, the star tracks would have it as their center of radius.
    >
    > now, I've not time to muck about with who is moving - actually any

    reference
    > frame is possible, however, some certainly lead to model simplifications.
    > in this case I choose to think of the camera as stationary.
    >
    > you must be confused, right?


    How can it appear stationary in the frame with the rotation of the Earth
    causing perceived movement?
     
    Mark M, Jul 22, 2003
    #9
  10. Mark N

    Alan F Cross Guest

    In message <PJ_Sa.2503$>, Mark N
    <> writes
    >Hi troops,
    >
    >i have just taken some star trail pictures and upon examination, have
    >noticed some pixels are unusually bright dont really belong in the image.
    >
    >I have heard about hot and dead pixels but dont know exactly what to look
    >for.
    >
    >could someone take a look at these 2 images and let me know what the hell is
    >going on here!!!
    >
    >http://www.marknowak.co.uk/images/pixel-1.jpg (17Kb)
    >http://www.marknowak.co.uk/images/pixel-2.jpg (65Kb)
    >
    >
    >There are a number of image 1 and 2 of image 2 in all of the images i have
    >taken this evening. I have only noticed these when taking star trail pics,
    >and so does not really affect the other types of photography i do
    >
    >
    >Thanks for any help, Mark
    >
    >


    Just take some long exposures with the lens cap on, then you'll know
    they are not heavenly bodies!
    --
    Alan F Cross
     
    Alan F Cross, Jul 22, 2003
    #10
  11. Mark N

    Jim Townsend Guest

    Mark M wrote:

    >
    > "ralford" <> wrote in message
    > news:pt9Ta.86160$...
    >> not kidding at all. Polaris would appear stationary in a time exposure,
    >> however, the star tracks would have it as their center of radius.

    >
    >
    > How can it appear stationary in the frame with the rotation of the Earth
    > causing perceived movement?


    http://members.aol.com/nlpjp/polaris.htm
     
    Jim Townsend, Jul 22, 2003
    #11
  12. Mark N

    George Kerby Guest

    On 7/22/03 6:45 AM, in article pt9Ta.86160$,
    "ralford" <> wrote:

    > not kidding at all. Polaris would appear stationary in a time exposure,
    > however, the star tracks would have it as their center of radius.
    >
    > now, I've not time to muck about with who is moving - actually any reference
    > frame is possible, however, some certainly lead to model simplifications.
    > in this case I choose to think of the camera as stationary.
    >
    > you must be confused, right?
    >
    > rma
    >
    > "Mark M" <> wrote in message
    > news:xP1Ta.13740$Bp2.13641@fed1read07...
    >>
    >> "ralford" <> wrote in message
    >> news:vj0Ta.82781$...
    >>> presuming these are images of stars moving across the frame, what

    >> celestial
    >>> body would have been stationary?

    >>
    >> You're kidding, right? :)
    >>
    >>

    >
    >

    Your ALL wrong. You live in Roswell, don't you!?!


    ______________________________________________________________________
    Posted Via Uncensored-News.Com - Still Only $9.95 - http://www.uncensored-news.com
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    George Kerby, Jul 22, 2003
    #12
  13. On Tue, 22 Jul 2003 01:26:30 +0100, "Mark N" <> wrote:

    >ok, i have posted a better image. its a 66% zoom into the image.
    >
    >http://www.marknowak.co.uk/images/pixel-3.jpg (59Kb)


    Looks familiar to me. I think you'll find this on all long exposures.
    It's a fairly common problem with consumer digicams under long
    exposure conditions.

    --
    Pete
    Homepage at http://www.pbl33.co.uk
    CCD/digicam astronomy
     
    Pete Lawrence, Jul 22, 2003
    #13
  14. Mark N

    Mark M Guest


    > > How can it appear stationary in the frame with the rotation of the Earth
    > > causing perceived movement?

    >
    > http://members.aol.com/nlpjp/polaris.htm


    Thanks.
    I didn't know that was it's name.
    :)
     
    Mark M, Jul 22, 2003
    #14
  15. "Mark N" <> writes:

    > i have just taken some star trail pictures and upon examination,
    > have noticed some pixels are unusually bright dont really belong in
    > the image.


    > I have heard about hot and dead pixels but dont know exactly what to
    > look for.


    Put the lens cap on, and close off the view finder. Shoot a set of
    frames over a time range up to 10 min or so. Get the *RAW* images and
    look at them. Set up a dim bulb a few metres in front of the camera,
    repeat.

    BTW, shot several frames for each setting, you will want to average
    them, and measure the Standard Deviation for each pixel.

    The first set gives you the noise and dark current of the camera. You
    will probably find a few pixels that have significantly higher dark
    current than average, hopefully over on the edges. The second lot will
    show and variation in gain between pixels, and will enable you to see
    where in the range you start getting non-linear data. With CMOS you not
    only see any pixel variation, but difference in the gain of that cell.

    The second you could do with Red, Green and Blue LEDs to get better
    data for each pixel. Make sure the light is dead in front of the
    camera so there is no shadow from the mirror box or mount on the CCD.
    Also, don't use too bright a light, you don't want to saturate things,
    and keep the distance largish so you do not have significant variation
    in distance.

    --
    Paul Repacholi 1 Crescent Rd.,
    +61 (08) 9257-1001 Kalamunda.
    West Australia 6076
    comp.os.vms,- The Older, Grumpier Slashdot
    Raw, Cooked or Well-done, it's all half baked.
    EPIC, The Architecture of the future, always has been, always will be.
     
    Paul Repacholi, Jul 25, 2003
    #15
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