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Prog Scan max screen size

Discussion in 'Projectors, Screens & Video Processors' started by graham.myers, Nov 26, 2001.

  1. graham.myers

    graham.myers
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    I'm contemplating goingto a progressive scan DVD.

    I read on a plrevious thread that there is a maximum projection size (6ft) I think.

    Why is this, I have a 7ft screen, what are the downs going over this 6ft limit (it there is one)
     
  2. Stuart Wright

    Stuart Wright
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    If you mean progressive scan from a stand alone DVD player then the problem is that they are limited to 480 lines. Stretch these out on a big screen and eventually you can see the gaps between them. Personally 6 foot is pushing it for me.
    People with home cinema PCs or scalers convert the output to have more lines - commonly 600, 720 or 960. You can blow the image up pretty large and not see the lines.
     
  3. Paul D

    Paul D
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    I think the progressive screen size, will be more important if you are using a CRT projector.

    LCD/DLP have scalers built in, so maybe these would still scale the image. This would remove any scan lines, allowing larger screens.

    On CRTs, it would depend on what make model it is. Ie some CRT can only show Video quality. Some are data quality, therefore sharper. So if the projector can resolve more lines, it needs more to avoid seeing the gaps etc.

    The trick is to match the lines to the projector, plus how old the tubes are.

    Example:-
    Brand new 8" CRT would be say quad lines, any more and the picture would soften due to line overlap. Any less and the gaps between them would start to show.
    Same 8" CRT with a load of hours on the tubes, would be less sharp. So quad lines would overlap, but tripling may look sharp etc.

    So if you are using a progressive scan player it would be doubling the lines as such. So stick with a LCD/DLP, or a lower spec CRT etc.

    PS i'm not 100% sure on all the above, but i'm sure the more knowledgeable will jump in!!
     
  4. graham.myers

    graham.myers
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    thanks guys, I'm using a sony 10HT so by the sound of it I think I'll be OK.

    I'll have to borrow a progressive scan DVD player and see what it looks like compared to the composite output of my current US pioneer 606
    (anybody want to buy my cx-850? I played with component this weekend and dont want to go back to s-video!)
     
  5. laurie

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    Hang on a minute

    If you have an 10ht my impression was that if you feed it an progressive signal it will by pass its internal scaler!
    on a pal disc my 10ht shows 576p/50 so where is the 480 coming from !!
    cheers Laurie
     
  6. Paul D

    Paul D
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    The sony must still scale both 480p(NTSC), and 576p(PAL). Because it still fills the 768 vertical panel (1366x768)etc.
    Otherwise you would end up with black bars top and bottom even on 4.3 material(which would also have black bars at the sides).
     
  7. tryingtimes

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    Just a note to all this (not necessarily useful to graham)
    The higher-end the crt projector, the higher the resolution of the source must be to avoid seeing scan lines. This is because as you go up the scale the projectors throw out finer and finer lines.

    If you were to use something like a Seleco 400/420/450, Barco 70X, or any other projector whose sweet spot is 480p then you should get a very smooth picture at 7 feet.
    These projectors have scan lines that will just meet at this resolution.

    Of course viewing distance has a large part to play.

    In the end the brightness of the projector might be the limiting factor - at more than 7 feet you will probably loose the image's punch.

    Of course, as usual this is all second hand information as I don't yet have a projector. Maybe someone can confirm?

    Cheers
    Alex
     
  8. mart.stokes

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    Does anybody know Alex well enough to confirm if he has a projector or not? I would have expected him to know himself! Alex, is there a big box hanging from the ceiling of your living room? If not then I doubt if you have a projector!
     
  9. tryingtimes

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    Who's Alex?
    I don't know him but I suspect he's just one of those people who talks about getting a projector for ages just so that he can participate in something resembling a community.

    Sad little man.
     
  10. mart.stokes

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    You must be my brother then! I'm exactly the same.

    The "list" is (was);

    New car for the wife (done, early 2000).
    Holiday to South Africa so the wife can see the animals (done, 2001).
    Install shower in main bathroom (planned early 2002).
    Replace en-suite bathroom (planned late 2002).
    Projector (early 2003).

    But I suspect the wife will manage to add a new block paving driveway and double glazing in somewhere which will throw me back to the next decade (by which time she will want another new car.....).
     
  11. tryingtimes

    tryingtimes
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    Hopefully my projector is only days away!
    I'm just starting to put the final touches on the (basic at present) HCPC.
    It's all coming together rather well except that my Gamecube never turned up :mad:
     
  12. laurie

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    Paul

    many thanks for your reply now I know why people go the HTPC way so am I'm to assume I'm better off not feeding my 10ht a progressive signal and let it do the scaling! if its has to scale the difference between 576p and 768p what is all the fuss about progressive scan dvd players..no actually I,m totally confused as to why people say the "DVO chip in the Denon 2800 is far better than the internal Sony one" I think I will just go a watch a movie
     
  13. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    When folk suggest using an external scaler with a VPL10HT it's usually for the following reason.

    As has been pointed out the Sony has to de-interlace all incoming interlaced signals, ie NTSC and PAL discs from non prog sources. It then scales this progressive image to fit it's native pixel array. There are two jobs here.

    The use of an external de-interlacer, like that in a DVD2800 or an Iscan or a decent scaler is that the DE-INTERLACING in these devices is superior to that of the VLP10. These external boxes usually have a thing called 3:2 pulldown detection and in some cases 2:2 pulldown detection. This feature allows them to outperform the Sony's internal de-interlacing when playing back video material sourced from original 24fps film. They recognise which fields in the interlaced image are from the same frame and re-constitute them together to create far less artifacts than the Sony can on its own. I won't go in to how they do this on this thread or what the benefits are. Go to this forums sponsor site www.progressivescan.co.uk and read about it there.

    The VPL11's internal de-interlacer has this feature and should make the addition of external devices not as clear cut as with the 10.

    Gordon
     
  14. laurie

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    Gordon

    Thanks a lot for the short but informative lesson..I'm getting there
    regards laurie
     

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