pinhole question

Discussion in 'Digital Photography' started by G.T., Jun 13, 2004.

  1. G.T.

    G.T. Guest

    I have a Digital Rebel and am basically just using foil with a pinhole
    at the moment. I took a photo of a black & white album cover with a 30
    second exposure and when I view it there are quite a few red and blue
    pixels and a couple of green pixels. I don't see this when I just shoot
    the album cover without the pinhole. What could be causing this? Is it
    just noise because of the long exposure and 800 iso?

    Greg
     
    G.T., Jun 13, 2004
    #1
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  2. Thirty seconds is a very long time for a digital exposure. In film
    photography you often get color shift and reduced sensitivity when you start
    using such long exposures. In digital you get "noise." What you describe
    sounds like noise. Some cameras have more of a problem than others, but I
    am guessing yours is just that due to the long exposure.
     
    Joseph Meehan, Jun 13, 2004
    #2
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  3. G.T.

    G.T. Guest

    Yeah, that's what I figured. I'll try some out where I don't need such
    a long exposure.

    Greg
     
    G.T., Jun 13, 2004
    #3
  4. G.T.

    Alan D-W Guest

    You expect perfection from turkey foil?
     
    Alan D-W, Jun 13, 2004
    #4
  5. G.T.

    Zol. Guest

    It`s probably the ISO but difficult to say exactly - I`d be interesed in seeing your results
    from a digital pinhole camera.

    regards, Zol.
     
    Zol., Jun 13, 2004
    #5
  6. G.T.

    G.T. Guest

    Actually I didn't expect anything. And it hardly matters what the
    material is as long it's opaque and the hole is smooth.

    Greg
     
    G.T., Jun 13, 2004
    #6
  7. G.T.

    Gener Guest

    I think anything smaller than 4x5 cut film will be too grainy, and
    impossible with digital. I made a 35mm panoramic pinhole camera
    and the results were very disappointing. Look for "Pinhole" at
    http://www.photoprojects.net/index9.html
    and the sample image upper right.
    Gene
     
    Gener, Jun 14, 2004
    #7
  8. G.T.

    Chris Brown Guest

    Probably. Long exposures and high ISO don't mix. I do all my long exposure
    stuff at 100 ISO, which is much cleaner.
     
    Chris Brown, Jun 14, 2004
    #8
  9. G.T.

    Martin Brown Guest

    Yes. Traditionally called hot pixels with higher than average leakage
    current. They become a nuisance on long time exposures.

    You can hide most of their effect by taking a matching exposure of the
    inside of your lens cap under identical conditions and then doing a dark
    frame subtraction in the post processing to eliminate instrumental
    artefacts. Some CCDs also have a warm corner where the readout
    electronics sit which also shows up brighter on long exposures.

    Regards,
     
    Martin Brown, Jun 14, 2004
    #9
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