Is This A Dead Pixel On My Sensor?

Discussion in 'Digital Photography' started by SolracSelbor, Feb 29, 2008.

  1. SolracSelbor macrumors 6502

    Joined:
    Nov 26, 2007
    #1
    The attachment is a 330% crop from the left side under the cloud of this image:

    [​IMG]

    I took both those pieces of dust off on photoshop using the spot cleaning tool, but that little bright dot shows up on all my photos. Sometimes its bright green, sometimes its bright white. Is this a dead pixel in my sensor or a hot pixel? I cleaned my sensor using a hand-held blower and most of the dust is gone except for this little bugger. Any suggestions on how to fix this?

    Pentax K10D
    18-55mm Lens

    P.S. I know i spelled pixel wrong on the image.
     

    Attached Files:

  2. iBallz macrumors 6502

    iBallz

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    Dec 31, 2007
    Location:
    So. Utah
    #2
    I dont know, but on a shot like that, dont ya wish you had a 5X7" field camera?
     
  3. ChrisA macrumors G4

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    Jan 5, 2006
    Location:
    Redondo Beach, California
    #3
    It is a "hot" pixel. Dead pixels are black. Well sort of, because as you
    know a sensor pixel is not the same as an image pixel, image pixels are interpolated from sensor pixels.


    The other one looks like dust. Dust is always slightly out of focus because it sits on top of the anti-alias filter not right on the plane of focus.

    There is a way to get rid of this. Astronomers always make a map of their sensors and apply a correction for both pixel gain (hot or dead just means a pixel with high or low gain) and dark current. A raw conversion program could apply such a correction. I think some do allow you to specify a kind of pixel list even if it is just a list of pixels to be ignored. Now that you ask I forget where I saw this but I do know there are some raw processors that will accept a "defect list" of pixels
     
  4. ChrisA macrumors G4

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    Jan 5, 2006
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    Redondo Beach, California
    #4
    Back when I was shooting film exclusively I had two camera systems, a 35mm Nikon and a 6x7 Mamiya RB67. Every time I good a good image with the Nikon I kicked myself for being so #$@% lazy and not using the RB67.

    I've got a project going where I'm scanning all my filled film. I put it into Aperture right along side my DSLR shots. The TIFFs from the scanner get about the same workflow as a RAW camera image. So I can see some digitized film in the same software as DSLR files. Oranges to Oranges. Gosh, what a huge difference. It's making me want to get back to using film for some subjects. As soon as I see a Hasselblad system or a Sinar P at a good price..... Or even a Holga.
     
  5. Hmac macrumors 68020

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    Midwest USA
    #5
    Yeh, that's a hot pixel.
     
  6. brendanryder macrumors 6502a

    brendanryder

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    Dec 28, 2006
    Location:
    Calgary
    #6

    A. its unnoticible, but things like that would bug the crap of me
    B. Try white out ?:D
     
  7. SolracSelbor thread starter macrumors 6502

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    Nov 26, 2007
    #7
    anyone got any suggestions on how to fix a hot pixel.
     
  8. jtblueberry macrumors regular

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    Dec 20, 2007
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    Pismo Beach, CA
    #8
    I just bought new cameras...a big part of the reason was dead pixels that I couldn't fix. I didn't know you could.
     
  9. Hmac macrumors 68020

    Joined:
    May 30, 2007
    Location:
    Midwest USA
    #9
    You can clone it out in your editing software, that's all you can do.

    If you send it back for service, they can remap your sensor. They'll go to that hot pixel and in the camera's firmware they'll replace its value with an average of the surrounding pixels.

    Hot or dead pixels are an inevitable consequence of digital imaging. A camera's sensor will always have some dead pixels, or pixels with varying degrees of charge leakage as an inevitable consequence of the manufacturing process, but before it leaves the factory, the sensor is "mapped" wherein all the identified bad pixels are cloned out so they're not visible. If the mfgr picked only sensors with NO bad pixels, the sensor yield would be ridiculously low and our cameras would cost much, much more than the do. So, theoretically, the camera should come from the factory with no visible bad pixels (depending on the diligence of the final assembly technician). However, multiple power cycles over time as you use the camera will ultimately cause MORE bad pixels to show up over time. That's likely what happened to you.

    Most high quality camera mfgrs wouldn't replace the sensor under warranty unless there was an entire row or block of bad pixels. They likely will re-map the sensor under the camera's warranty.That's something I've done on a couple of occasions - just before the warranty runs out, send it in to factory service complaining of occasional focusing errors and hot or dead pixels. A quality camera mfgr will calibrate the AF, remap the sensor, and clean it up.

    If you want to check for more bad pixels (you certainly will have more than just that one), download and run Dead Pixel Test . Warning, you may not be happy with the results.
     
  10. Hmac macrumors 68020

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    Midwest USA
    #10
    Some true audiophiles long for vinyl LPs in much the same way. Won't be long, I suspect, that film will be as dead as the vinyl LP.
     
  11. jtblueberry macrumors regular

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    Pismo Beach, CA
    #11
    Any idea how much this would cost out of warranty?
     
  12. Hmac macrumors 68020

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    May 30, 2007
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    Midwest USA
    #12
    No clue. It will vary from mfgr to mfgr, I'm sure.

    If I were looking to remap out of warranty, I'd start calling authorized service centers and see if they have the software necessary to do that and check pricing. If they do, I suspect an authorized service center would be cheaper than factory service.

    Many digital photographers are waiting for someone to come out with software that allows the end-user to remap the sensor themselves. That's unlikely to happen - they've been waiting for years. It would be theoretically possible, however, for the camera to be able to remap itself...and some will do that using "long-exposure noise reduction" or something similar. Note that if you take a long enough exposure, you will inevitably get some degree of bad pixels showing up. Normal and inevitable variations in pixel charging usually are minimal in short exposures, really begin to show up the longer the pixel is charged.
     
  13. bocomo macrumors 6502

    Joined:
    Jun 29, 2007
    Location:
    New York
    #13
    yep, it's called dark frame subtraction (pretty cool sounding, no?) usually made active in your camera by turning on long exposure noise reduction or done in post:

    http://www.ddisoftware.com/qimage/qimagehlp/dark.htm

    http://www.takegreatpictures.com/HO...tion_using_Adobe_Photoshopby_Chris_Limone.fci

    http://www.astropix.com/HTML/J_DIGIT/JPG_DFS.HTM

    http://en.wikipedia.org/wiki/Dark_frame_subtraction

    http://www.anandtech.com/digitalcameras/showdoc.aspx?i=2351&p=2

    i love a good geek-out :)
     
  14. SonicChronicler macrumors member

    SonicChronicler

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    Aug 19, 2007
    Location:
    In the Wilds....Northumberland, UK
    #14
    The Vinyl album is far from being Dead my friend - but I suppose it depends what type of music you are looking for.

    Sonic
     
  15. Hmac macrumors 68020

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    May 30, 2007
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    Midwest USA
    #15
    Dead, sorry. Vinyl died the day Target stopped carrying LP's. Film....?...Not very far behind. I think you can still buy some film at Target or Wal Mart, but not for long, I bet. All soon to be the sole provinces of curmudgeonly "enthusiasts".

    [​IMG]...just an opinion.
     
  16. sonor macrumors 6502

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    Jan 15, 2008
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    London, UK
    #16
    Maybe in the US, but it's not doing so badly in the UK - actually had a bit of a resurgence in the last few years...and still the preferred medium for most club DJs.
     
  17. EssentialParado macrumors 65816

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    Feb 17, 2005
    #17
    Debatable :)

    I know vinyl has dropped in popularity in Europe. We stopped producing vinyl in 2006 after it stopped being cost effective for my record label.
     

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