television

Discussion in 'Photography Beginners' Forum' started by julie32, May 12, 2008.

  1. julie32

    julie32 TPF Noob!

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    Also--- how can I take a decent photo of a television program without the thick bands that are viewable across the screen..is it possible?

    thanks
     
  2. LaFoto

    LaFoto Just Corinna in real life Staff Member Supporting Member

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    Yes. It is possible. I think your exposure time must not be any slower than 1/60 sec. I have taken photos off the old screen, and taken them off the new one (flat television, I don't know if the picture creates itself in the same manner on the new flat ones), and even those off the old screen mostly came out without the black band across the screen.
     
  3. Crosby

    Crosby TPF Noob!

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    I don't think so unless you use a longer shutter speed.

    Shoot an LCD TV screen. I don't think that will produce those dark bands.
     
  4. Valethar

    Valethar TPF Noob!

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    The problem is going to be the refresh on the screen. The bands you are seeing are a result of the photon guns in the back of the picture tube updating the image on the screen, which is done in a strobe-like fashion. This is what creates the moving wavy lines you see when someone has a video camera aimed at a TV screen, or the banding on a still picture.

    As Crosby mentioned, LCD screens may not give you this headache. I've never taken a picture of an LCD, so I don't know for certain.

    I did a quick Google search and found an article that may help. It's a bit dated, but if you're taking a picture of a standard glass tubed television, is should still give you something to work with.

    http://www.halfhill.com/archive.html
     
  5. Snyder

    Snyder TPF Noob!

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    you can record what you want onto miniDV import onto your PC then take a screen cap of it using adobe premier. native resolution for SD is 720x480 but is perfect picture quality.
     
  6. ThePup

    ThePup TPF Noob!

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    It's actually pretty easy to take a photo of a telly - The shutter speed needs to be SLOWER than the refresh rate of the television. For PAL this is 50Hz, NTSC is 60Hz. (So, SLOWER than 1/50th or 1/60th of a second.)
     
  7. totalmajor

    totalmajor TPF Noob!

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    you got it!
     
  8. Early

    Early TPF Noob!

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    They used to tell us 1/30th of a sec or slower. Please don't ask who they are.
     
  9. Valethar

    Valethar TPF Noob!

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    The Men in Black?
     
  10. Helen B

    Helen B TPF Noob!

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    It's better to do it at twice that exposure for CRTs at the very least - four times is better. PAL is 25 frames per second, NTSC is 30 frames per second. There are two interlacing fields per frame, hence the 'refresh' rates of 50 Hz and 60 Hz. You need to allow both fields to refresh fully as an absolute minimum (for CRTs).

    Best,
    Helen
     
  11. Judge Sharpe

    Judge Sharpe TPF Noob!

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    Avoid multipals or divisors of 60. because of the 60 cycle/ second refreash in the tube. Think of the wagon wheels in an old western when they turned at 60 rpm the looked to stand still. More than 60, they semmed to spin forward, less than 60 the looked like they were spinning backward.
    Judge Sharpe
     
  12. JamesD

    JamesD Between darkrooms

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    For NTSC video (In the US) and also PAL video (I think) there are actually two complete sweeps required to get the whole image. Although one sweep takes 1/60th sec (for NTSC), that only paints every other line on the screen--the odd-numbered lines, if you will. The next sweep paints the even-numbered lines.

    Set your shutter speed to 1/30th sec. As Helen B says, you might want to set it for longer, (in factors of 1/30... ie, 1/15, 1/10 etc); however, this will expose several video frames, giving you essentially a multiple exposure. Not a problem if the image on the screen is fixed, but for action scenes, it effectively gives you incremental motion blur.
     

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