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HS10 - use all the pixels for non 16:9 (1:1.85, 1:2.35 etc)

Discussion in 'Projectors, Screens & Video Processors' started by ziglar, Jan 20, 2003.

  1. ziglar

    ziglar
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    Hopefully this isn't a dopey question and my explanation means something!

    When projecting non 16:9 material you obviously still get black bars at the top & bottom of a 16:9 screen; I am assuming that the black(grey!?) bars still use some of the HS10's 788 vertical pixels?.

    Is it possible to 'unsqueeze' the picture so that it uses the full 788 pixels but still keeps the aspect ratio intact (so that the bars at top&bottom are not actually part of the visible projected output).

    Thanks

    btw I made my own screen from blackout material and it is definitely better than a beige wall but I'm sure it can still improve.
     
  2. John_N

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    Hi

    The grey bars top and bottom are indeed using some of the projectors resolution. The resultion of a DVD however has a maximum number of lines of 576 active lines to display on our PAL 612 system. Therefore the projector will be performing upscaling on any image to fit it onto the panel - which means that if our DVDs had more detail they would look better - but you aren't losing any detail by having the bars.

    You can not stretch the picture without altering the aspect ratio unless you decide to 'crop' the sides.

    My solution to DVDs with slightly different aspect ratio is to use the projector 'zoom' and zoom the image to fit. This only works on my install at the moment because I have an odd-sized white rectangle on the wall that is not quite 16:9 ratio.
     
  3. Gary Lightfoot

    Gary Lightfoot
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    If you use a computer with DVD player, and someything like WinDVD and YXY software, you should then be able to make a 2.35:1 movie fit a 16:9 screen whilst keeping the correct aspect ratio, but losing some image off of the sides.

    That's providing that you can do pixel perfect mapping with that particular projector - I have a feeling there's a bit of a trick to it (look in the home cinema pc forum), and you may have to use Powerstrip software.

    More ino is available over at the hcpc forum.

    HTH

    Gary.
     
  4. John_N

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    Yes. Like I said - you'll crop the image and lose information at the sides. Since you won't actually GAIN anything because of the number of active lines on the DVD, I personally wouldn't bother.

    :)

    Can you not use your projector zoom control to zoom the image even slightly to make the bars less of an annoyance?
     
  5. ziglar

    ziglar
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    I suspect I haven't made myself clear.

    I do not want to change the aspect ratio - it is essential that it remain as it is.

    Maybe if someone can answer the following questions then I will understand better:

    If I assume a PAL DVD (576 active lines); in a 16:9 film are ALL the lines used for the visible vertical resolution. Same question for 1:1.85 and 1:2.35.

    If I now assume a 16:9 screen at 80" x 45"; a 16:9 will fill the screen vertically with 576 lines per 45" = 12.8 lines/inch. A DVD recorded in 1:2.35 at 80" wide will be 34" vertically to keep the aspect ratio; will I get 576/34 = 16.9 lines/inch (i.e. a higher vertical pixel density) or still get 12.8 lines/inch??

    If the answer is a higher density then I am a happy bunny.

    For the time being ignore the 'upscaling' to map 576 lines to 788 (HS10 vertical resolution).

    Thanks for all answers to all my questions so far.
     
  6. richard plumb

    richard plumb
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    in a 1.78:1 movie (16:9), you get all 576(ish) lines as visible image.

    In a 1.85:1 movie, you still get all 576 lines as visible image, but some of that visible image is black lines.

    This is necessary because the image is always output as 4:3, then stretched horizontally to recreate the correct ratio. This stretch is always by the same amount, so for wider original ratios, the width is the same so the height must be reduced.

    So viewing on a big screen, 1.78:1 will fill it; 2.35:1 will fill the width but not the height.

    Density of lines will remain constant because the actual output of the DVD player is constant, just more or less of them are black.
     
  7. Gary Lightfoot

    Gary Lightfoot
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    You'll only get 12.8 lines per inch - the amount of lines used is reduced because the rest of the 576 lines are used for black bars.

    As the 576 is upscaled to 768, you'll get 1366 x 768 for 16:9, and 1366 x 581 for 2.35:1 material - the other 188 lines will be used for black bars (94 top, and 94 bottom).

    In the cinema you normaly see constant height, but variable width (the curtains slide sideways to allow a wider image). With a pj, you have a constant width, so different aspect ratios can normaly be achieved by varying the height. This is done by reducing the amoubt of lines used fro scope movies.

    The only way to use the full panel is to use a pc so that the image is deliberately made too high for the width, and use an anamorphic lens like the Panamorph or Isco to opticaly squish the image to the corrct aspect ratio.

    Edit - Richard - just noticed you beat me to it by nine measly minutes. :)

    HTH

    Gary.
     

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