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Thread: Colored Specks from high ISO

  1. #1
    Member Crappinni's Avatar
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    Default Colored Specks from high ISO

    Hello guys,

    I recently discovered a small problem. I took a couple of test shots without a lens and with the mount cap on (therefore complete darkness) with varying ISOs (RAW, manual mode, everything else constant). I found that at higher (3200) ISOs, obvious green/blue specks appear but at lower (50, 100) ISOs, they're non-existent/very small. Oddly, when I compress it to JPEG, the spots become extremely difficult to spot so no picture is included.

    Any idea what the problem is?

  2. #2
    Senior Member CS TAN's Avatar
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    Default Re: Colored Specks from high ISO

    Hot pixels.

    This is very common with digital sensors. Really depends on your luck as some camera will have less and some will have more. If the hot pixels bunched up together in one place, perhaps you can go to service center for them to take a look at. If it scatters around, it should not affect picture quality in most cases.
    Last edited by CS TAN; 19th December 2009 at 03:11 AM.
    Canon 5D Mark II | 24-105L | 35L | 85L II | 135L | Samyang 14mm 2.8

  3. #3
    Member Crappinni's Avatar
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    Default Re: Colored Specks from high ISO

    Thanks for the quick response. That's pretty sad. I never noticed them until recently so is it possible that the condition deteriorates? I've always discriminated my photos to the pixel and never saw anything.

  4. #4
    Deregistered shaoken's Avatar
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    Default Re: Colored Specks from high ISO

    Those are hot pixels. I ever encountered that before.
    Try this software to fix the hot pixels.

  5. #5

    Default Re: Colored Specks from high ISO

    Also, it's high ISO noise. It's normal. When you shoot as JPEG, the camera tries to clean up some of the noise.

    Since you're a pixel-peeper, I suggest never shooting above 200 ISO.
    Alpha

  6. #6
    Member Crappinni's Avatar
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    Default Re: Colored Specks from high ISO

    Thanks! I only started shooting long exposure quite recently (acquired a decent tripod). I realise I can enable long exposure noise reduction which solves the problem too (each shot takes longer to process though).

  7. #7

    Default Re: Colored Specks from high ISO

    usually negligible.

    but if the weather is warm, or your camera is hot due to usage (20 x 4min exposure with 1min interval on a warm night), these hot pixels can appear more frequently.

    unless you are super anal about it. there are softwares to "subtract" these hotpixels from your images. these methods are commonly used in astro photography.

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