Long Exposure Noise - Reducing

Discussion in 'Digital Photography' started by Cooter, Nov 8, 2003.

  1. Cooter

    Cooter Guest

    I recall reading that making an exposure with the lens cap on, then
    combining it with the image exposure is a good way to eliminate or at least
    reduce long exposure noise. What I don't remember is which blending mode
    should be used. Anyone know?

    Thanks,
    Cooter
     
    Cooter, Nov 8, 2003
    #1
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  2. "Cooter" <> wrote in message
    news:Fn8rb.81532$...
    > I recall reading that making an exposure with the lens cap on, then
    > combining it with the image exposure is a good way to eliminate or at

    least
    > reduce long exposure noise. What I don't remember is which blending mode
    > should be used. Anyone know?


    I don't think that will work with random noise.
     
    Charles Schuler, Nov 8, 2003
    #2
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  3. Cooter

    gr Guest

    "Charles Schuler" <> wrote
    >
    > "Cooter" <> wrote in message
    > news:Fn8rb.81532$...
    > > I recall reading that making an exposure with the lens cap on, then
    > > combining it with the image exposure is a good way to eliminate or at

    > least
    > > reduce long exposure noise. What I don't remember is which blending mode
    > > should be used. Anyone know?

    >
    > I don't think that will work with random noise.


    It works for getting rid of hox pixel noise, if your camera doesn't have
    built-in noise reduction.
     
    gr, Nov 8, 2003
    #3
  4. Cooter

    Scott Barnes Guest

    From what I understand, smaller CCD cameras generate random noise with
    longer exposures at high ISO that can be minimized by keeping the CCD cooler
    (turn off the camera for a few minutes between pictures), use a tripod and
    turn anti-shake features off (in the case of the A1), use lower ISO where
    possible, use a flash instead of long exposures.

    I agree with the others that the method you are describing is for hot
    pixels.

    If you take pictures that can't work around the noise issue, noise can be
    reduced with software such as:

    http://www.neatimage.com/ (Neat Image)
    http://www.picturecode.com/ (Noise Ninja)

    Scott

    "Cooter" <> wrote
    > I recall reading that making an exposure with the lens cap on, then
    > combining it with the image exposure is a good way to eliminate or at

    least
    > reduce long exposure noise. What I don't remember is which blending mode
    > should be used. Anyone know?
    > Thanks,
    > Cooter
     
    Scott Barnes, Nov 8, 2003
    #4
  5. Cooter

    KenJr Guest

    In article <Fn8rb.81532$>,
    says...
    > I recall reading that making an exposure with the lens cap on, then
    > combining it with the image exposure is a good way to eliminate or at least
    > reduce long exposure noise. What I don't remember is which blending mode
    > should be used. Anyone know?
    >
    > Thanks,
    > Cooter
    >
    >
    >


    When I'm taking long exposures I take one picture with the lens cap on
    and the next of the object I'm photographing. Two things to keep in mind
    are that both pictures should be taken at the same shutter speed and you
    should set your camera to save the file in a non-compressed format such
    as TIFF. Saving as a Jpeg adds jpeg artifacts to the noise. With daylight
    or flash pictures this isn't ussually a problem.

    After the pictures are in your computer load them into a editing program
    that supports layers such as Photoshop. Load the good exposure then into
    a seperate layer load the exposure with the lens cap on. Subtract this
    one from the good layer and most of the niose should be eliminated. Save
    this file under a different name than you original picture.


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    KenJr, Nov 8, 2003
    #5
  6. Cooter

    Don Stauffer Guest

    That only works with fixed pattern noise, which is not the sort that
    bothers you in long exposures.

    Cooter wrote:
    >
    > I recall reading that making an exposure with the lens cap on, then
    > combining it with the image exposure is a good way to eliminate or at least
    > reduce long exposure noise. What I don't remember is which blending mode
    > should be used. Anyone know?
    >
    > Thanks,
    > Cooter


    --
    Don Stauffer in Minnesota

    webpage- http://www.usfamily.net/web/stauffer
     
    Don Stauffer, Nov 9, 2003
    #6
  7. Cooter

    Ed Ruf Guest

    On Sat, 08 Nov 2003 15:57:25 GMT, in rec.photo.digital "Cooter"
    <> wrote:

    >I recall reading that making an exposure with the lens cap on, then
    >combining it with the image exposure is a good way to eliminate or at least
    >reduce long exposure noise. What I don't remember is which blending mode
    >should be used. Anyone know?


    Give the Neat Image demo a try.
    ________________________________________________________
    Ed Ruf Lifetime AMA# 344007 ()
    http://members.cox.net/egruf
    See images taken with my CP-990 and 5700 at
    http://members.cox.net/egruf-digicam
     
    Ed Ruf, Nov 9, 2003
    #7
  8. Cooter

    Don Coon Guest

    Take a look at "Black Frame" free from MediaChance:
    http://www.mediachance.com/digicam/blackframe.htm

    Good Luck!

    "Don Stauffer" <> wrote in message
    news:...
    > That only works with fixed pattern noise, which is not the sort that
    > bothers you in long exposures.
    >
    > Cooter wrote:
    > >
    > > I recall reading that making an exposure with the lens cap on, then
    > > combining it with the image exposure is a good way to eliminate or at

    least
    > > reduce long exposure noise. What I don't remember is which blending mode
    > > should be used. Anyone know?
    > >
    > > Thanks,
    > > Cooter

    >
    > --
    > Don Stauffer in Minnesota
    >
    > webpage- http://www.usfamily.net/web/stauffer
     
    Don Coon, Nov 9, 2003
    #8
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