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When is 720p Not 720p?

Posted by Hemos on from the the-tricks-of-the-eye dept.

Henning Hoffmann writes "HDBlog has an interesting entry about many home theater displays.
Home theater displays around the resolution of 720p (most DLP, LCD, and LCOS displays) must convert 1080i material to their native resolution for display. No surprise there. But many displays do this by discarding half of the 1080i HD signal, effectively giving 720p viewers an SD signal - not watching HD at all! "

4 of 399 comments (clear)

  1. Which Models? by goldspider · · Score: 5, Interesting

    Is there any way of telling which sets do this? This is certainly something I'd like to know before I dropped that kind of cash.

    --
    "Ask not what your country can do for you." --John F. Kennedy
    1. Re:Which Models? by David+Leppik · · Score: 5, Interesting
      Is there any way of telling which sets do this? This is certainly something I'd like to know before I dropped that kind of cash.
      Yes. Go to a showroom and look at the displays. If you see some that have greater vertical resolution than the non-HD models, there you go. If you can't see a difference, then it doesn't make a difference.

      If there is a difference you can't see but could learn to see, don't learn; it will not bring you joy, it will only make you miserable or annoying. Long ago I learned to see the FFT distortion in JPEG and MPEG images. Has it made me happy? No. I end up making the JPEGs on my website bigger than everyone else's so I won't see wrinkles on people's faces that are apparently invisible to everyone else. And I can't stand to watch satellite television on a big screen TV because of the annoying compression artifacts.

  2. How to prove/disprove it easily. by Stavr0 · · Score: 4, Interesting
    Simply provide a 1080i test pattern made of alternating horizontal lines where the left half is black lines on even scanlines, white lines on odd scanlines and the right half is reversed (white-even,black-odd)

    The results may be one of the following:

    You will get a screen full of tiny, shimmering horizontal lines that shift in the center of your screen Congratulations! Your HT gear is showing a true 1080i picture You will get a full screen of gray, possibly with a line in the center Not bad, your gear is properly downscaling the signal Half your screen is black, the other is white Uh oh. Your gear is taking the easy way out and dropping half the scanlines to downconvert (Bele and Lokai) I call that the Cheron Test.
  3. Shameless Atari / Amiga Plug by tjstork · · Score: 5, Interesting

    Back in the day, on the Atari and Amiga, you could actually do stuff in that interrupt time. The most common thing was to swap display buffers for double buffering. This made for rock steady hardware scrolling, an effect that still lacks somewhat in today's PC's, believe it or not, as there was absolutely no tearing of the display whatsover. Just a beautiful effect.

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    This is my sig.