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Thread: Colour noise during long exposure?

  1. #1

    Default Colour noise during long exposure?

    Hi Bros and Sis,

    I took a long exposure shot with my NEX-6 and the rokinon 8mm Fisheye lens, and I noticed some strange colour pixels in the shadow areas. I uploaded the full-res pic, please take a look at the forest areas in my picture (at 100%). The pixels were not very noticeable (but is there) in the raw files. I did some PP to bring back some shadow details and the colour pixels become very apparent. Anyone knows why? Is it because of my lens? sensor? long-exposure NR, or the lack of it (I did not turn on LE NR)? Or are there really spirits living in the forests?

    Taken at f/8 ISO 200 exposure 25s

    hi

  2. #2

    Default Re: Colour noise during long exposure?

    Quote Originally Posted by silvermoon1407 View Post
    Hi Bros and Sis,

    I took a long exposure shot with my NEX-6 and the rokinon 8mm Fisheye lens, and I noticed some strange colour pixels in the shadow areas. I uploaded the full-res pic, please take a look at the forest areas in my picture (at 100%). The pixels were not very noticeable (but is there) in the raw files. I did some PP to bring back some shadow details and the colour pixels become very apparent. Anyone knows why? Is it because of my lens? sensor? long-exposure NR, or the lack of it (I did not turn on LE NR)? Or are there really spirits living in the forests?

    Taken at f/8 ISO 200 exposure 25s
    bizarre. Did you try with DRO off?
    Alpha

  3. #3
    Senior Member digitalpimp's Avatar
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    Default

    I can't see them (I'm on mobile), but the way you describe them leads me to believe they are hot pixels. It happens when you do long exposures with the LENR off. Although I kinda find it odd they manifest in just 25 secs. Try shooting again with the LENR on and see if the hot pixels still show.

  4. #4

    Default Re: Colour noise during long exposure?

    Quote Originally Posted by digitalpimp View Post
    I can't see them (I'm on mobile), but the way you describe them leads me to believe they are hot pixels. It happens when you do long exposures with the LENR off. Although I kinda find it odd they manifest in just 25 secs. Try shooting again with the LENR on and see if the hot pixels still show.
    I shall try again with LENR on. Hmm, not very familiar with hot pixels, but if they manifest in just 25 s, does it mean it's a bad thing?

    Quote Originally Posted by Rashkae View Post
    bizarre. Did you try with DRO off?
    DRO was on auto. It affects raw files?
    hi

  5. #5
    Senior Member digitalpimp's Avatar
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    Quote Originally Posted by silvermoon1407 View Post

    I shall try again with LENR on. Hmm, not very familiar with hot pixels, but if they manifest in just 25 s, does it mean it's a bad thing?
    I'm assuming it is (note: I'm no expert). Your ISO may have also contributed. Personally, I wouldn't do long exposures at ISO200, with or without hot pixels. Anyway, keep your lens cap attached when you do your test so you'll see exactly where and how many your dead pixels are.

    Just to share with you my longest single exposure using an A700. That's 30 minutes without LENR. Never got to try with LENR turned on though.


    My A77 can go 12 minutes+ without glitch, and my A300 can do 4.

  6. #6

    Default

    Quote Originally Posted by silvermoon1407 View Post
    Hi Bros and Sis,

    I took a long exposure shot with my NEX-6 and the rokinon 8mm Fisheye lens, and I noticed some strange colour pixels in the shadow areas. I uploaded the full-res pic, please take a look at the forest areas in my picture (at 100%). The pixels were not very noticeable (but is there) in the raw files. I did some PP to bring back some shadow details and the colour pixels become very apparent. Anyone knows why? Is it because of my lens? sensor? long-exposure NR, or the lack of it (I did not turn on LE NR)? Or are there really spirits living in the forests?

    Taken at f/8 ISO 200 exposure 25s
    Try doing at f/10 or 12 at lowest ISO

  7. #7

    Default

    That's an unusually high amount of hot pixels.
    Alpha

  8. #8

    Default

    Quote Originally Posted by donut88 View Post

    Try doing at f/10 or 12 at lowest ISO
    Exposure time will be longer, how would it help?
    hi

  9. #9
    Moderator catchlights's Avatar
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    Default Re: Colour noise during long exposure?

    just hot pixel, a by product of long exposure.
    Shoot to Live, Live to Shoot
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