Q about very long exposures

Discussion in 'Digital SLR' started by Toby, Nov 28, 2006.

  1. Toby

    Toby Guest

    I have a D200 which works fine in "normal" circumstances. However I tried to
    do a long night exposure--about 3 minutes--and found that the top sides and
    bottom middle of the frame were "washed out" with pink flare--looking almost
    like light-struck film. Further tests showed that this was always in the
    same place, appearing at about 1 minute exposure, and growing in strength
    and size as the exposure time increased.

    Is this normal? I have seen digital pix done with very long exposures that
    looked fine. I'm running to the end of my warranty--should this be brought
    back to Nikon?

    TIA for any advice,

    Toby
     
    Toby, Nov 28, 2006
    #1
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  2. Did you enable the dark frame subtraction? Effects at the edges are, I
    understand, to the sensor becoming warm and the dark current increasing.
    Dark frame subtraction may reduce the effect of the abnormally high dark
    current, although it doubles the exposure time, presumably making the
    sensor even warmer....

    David
     
    David J Taylor, Nov 28, 2006
    #2
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  3. Toby

    Pete D Guest

    Does the D200 do dark frame subtraction noise reduction, if so then turn it
    on and try again.
     
    Pete D, Nov 28, 2006
    #3
  4. Toby

    Pete D Guest

  5. At what ISO? If it does this at ISO 100, it's strange. Mine only starts
    showing some of this around 10-15min at ISO 100. With dark frame
    subtraction, I have exposures at several minutes at ISO 800 which do
    not show this problem. In short, switch on DFS (ie "Long exp NR") to
    get rid of this. You do pay a price in time, though.
     
    achilleaslazarides, Nov 28, 2006
    #5
  6. Is there any chance that light entered the eyepiece?
     
    Charles Schuler, Nov 28, 2006
    #6
  7. Toby

    Toby Guest

    You have answered my question. I was exposing at ISO 1600, so I imagine that
    it is quite normal for the "purple haze" to appear after 3 mins at that high
    setting. Many thanks to all for taking the time to enlighten me.

    Cheers,

    Toby
     
    Toby, Nov 29, 2006
    #7
  8. Toby

    eawckyegcy Guest

    google up "amplifier glow"
     
    eawckyegcy, Nov 29, 2006
    #8
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