take a picture of a picture

Discussion in 'Digital Photography' started by Pete, Oct 7, 2007.

  1. Pete

    Pete Guest

    Suppose that I want to take a picture of a digital camera to show that
    its working.

    The camera shows a clear picture on it's screen. So, I photograph that.

    That, of course gives me a pixelated image of a pixelated image,
    and comes out crappy. I'm sure there must be a technical term for this,
    which you will no doubt tell me.

    see http://tinyurl.com/27pbaa for an example of what I mean.

    Any tips on getting a better image of the screen?
     
    Pete, Oct 7, 2007
    #1
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  2. Pete

    Bill Guest

    As the pixels on the lcd are constantly being refreshed in some order,
    a picture of the screen will (almost?) always show some missing
    pixels. Try shooting at the slowest shutter speed possible. You
    MIGHT get a decent resut.

    Bill

    BTW. Try shooting an led gas price sign. See how much of the price
    is missing :0)
     
    Bill, Oct 8, 2007
    #2
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  3. Pete

    RBrickston Guest

    Set the camera up on a tripod in front of a mirror, set the delayed
    shutter release, step out of the frame... voila.
     
    RBrickston, Oct 8, 2007
    #3
  4. Most P&S camera LCD/EVF displays refresh at rates well above 60fps
    non-interlaced, as much as 180 fps or more, slower shutter speeds will not
    matter much. This is how LCD/EVF viewfinders are able to keep up with the faster
    shutter speeds to show you what is happening as you increase it. They still show
    you the exact effect seen at 1/3200th of a second, but with dropped frames in
    the viewfinder.

    You'll need to feed your video-out from your camera into a computer video card
    that allows for video input. Then do a frame grab from that video signal for
    highest resolution available. If you don't have a video-card with video-input
    then a clunky work-around would be to display it on a TV through its video-input
    connection. Photograph the TV's screen. It has a higher-resolution digital or
    smoother analog display than most LCD/EVF screens in cameras. When using a TV
    display then you do have to remember to keep your shutter speed at 1/30th second
    or less to capture both interlaced frames. Take several photos to try to get one
    where the interlace exposure overlap occurs off-screen. Otherwise you will end
    up with a band of light or dark across your image where the 3rd frame from the
    2nd interlaced pair is being refreshed or hasn't started up just yet. Adding or
    subtracting from the exposure in that area. As accurate as you might think your
    camera's shutter speed is, it will clearly be shown when trying to photograph an
    interlaced video display and noting the amount of overlap of interlaced frames.
    You can even test its high shutter-speed accuracy by counting the number of
    scan-lines recorded. (This won't work with a dslr, because of the focal plane
    shutter distorting the shape of anything that moves fast.)
     
    barry woodsmith, Oct 8, 2007
    #4
  5. Pete

    irwell Guest

    Use the video out function, then a screen capture.
     
    irwell, Oct 8, 2007
    #5
  6. Pete

    Steven Guest

    What about using "Play" on the camera you are trying to photograph. That way
    it won't be refreshing the screen and you might get a better picture. Or
    alternatively use something like Photoshop and overlay the picture onto the
    screen but not in a way it looks false.


    Steven.
     
    Steven, Oct 8, 2007
    #6
  7. The problem in that image is timing and refresh rates, not pixellation.
     
    Chris Malcolm, Oct 14, 2007
    #7
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