Why 720?

Discussion in 'General TV Discussions Forum' started by rbrian, Feb 2, 2009.

  1. rbrian

    rbrian
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    Why are most HD sources 720? I'm not comparing it to 1080, that's a whole other discussion... What I mean is why isn't it 768? Back in the 4:3 days, 1024x768 was a standard PC screen resolution. This makes sense, 1024 is a round number in binary, and 768 is 3/4 of it. To make it 16:9 widescreen, it becomes 1366x768, which again makes relatively simple mathematical sense. So, HD ready screens are 1366x768... yet HD is mostly 720. Why? Surely it would look better at 768, with 1:1 pixel mapping? Alternatively, wouldn't the TV manufacturers save money by shaving a few pixels off and making 1280x720 screens?
     
  2. Trollslayer

    Trollslayer
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    480 * 1.5 = 720, the 768 is for overscan.
    Also, 576 * 1.25 = 720
     
  3. dovercat

    dovercat
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    I think it comes down to average visual acuity and typical viewing distances. 720p is the minimum resolution needed for 42" flat screen TVs at typical 10ft viewing distance.

    Home Theater: Viewing Distance vs. Resolution

    "Most people sit about 10 feet from their TVs. At this distance (and everything else being equal), your eye can resolve objects that are 0.033 inches wide"

    "42-inch-diagonal TV 1,280-by-720 plasma or LCD display has pixels that are roughly 0.029 inches wide"

    "50-inch-diagonal TV set the pixels in a 1,280-by-720 display are 0.034 inches wide. A 1,920-by-1,080 display has 0.023-inch-wide pixels.

    "A 1,920-by-1,080 display would have to measure more than 70 inches diagonally before you start testing your eyes' limits on the display's resolution (at least at 10 feet)"

    Ideally you want the display to occupy 30degrees of your vision, at 10ft this would mean a 74 inch diagonal screen.
     
    Last edited by a moderator: Feb 3, 2009

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