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Best projector resolution for 2.35 PAL films

Discussion in 'Projectors, Screens & Video Processors' started by stauDLP, Dec 17, 2004.

  1. stauDLP

    stauDLP
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    Hi to all,
    I'm new in this forum :hiya: and I hope I' ve not opened an old thread.

    I'd like to know which is the best resolution for a projector for 2.35 PAL film, like The Lords og the Rings, or Star wars, for instance.... etc... etc...
    I'll tell you hereafter what i think about:

    i believe that if I have a native 16/9 1024x576 lines projector - for instance equipped with the matterhorn chip (HC900, XVZ201...)- I cannot exploit all the resolution of the chip, in fact:

    to maintain the 2.35 aspect ratio of the film I would need 1024/2.35 =435 horizontal lines.
    435 lines!! It means that I'm not exploiting all my dvd definition!!
    I had 576 lines, but now in that format my chip has only 435 lines !!!

    The choice to see good 2.35 should be therefore to buy a 1280x720 projector:

    1280/2.35=544 lines

    I could make some mistakes, perhaps because the real format is not 2.35, but something less, but please correct if I'm totally wrong. :lease:

    StauDLP
     
  2. joffonon

    joffonon
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    The greater the resolution of your projector, the better a picture you can achieve (subject to the quality of the scaler when upscaling to greater than the native resolution of the source material).

    In other words, a 1280x720 chip should always, in theory, give you a better quality picture than a 1024x576 chip.
     
  3. stauDLP

    stauDLP
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    Ok Joffonon,
    thanks for your answer.
    But am I right with those calculations?
    What i meant is that you are wrong if you buy a 1024x576 matterhorn chip thinking that it would be perfectly suited to pal dvd disk: when viewing a 2.35 film, your projector won't be able to meet the resolution of the dvd disk.
    I agree when you say: " .....In other words, a 1280x720 chip should always, in theory, give you a better quality picture than a 1024x576 chip...." but in our case we have even lost of information.
    In 16/9 case the mustang 1280x720 chip would increase definition but dvd information would always be the same.
    To summarize: 1024x576 (matterhorn DLP for instance) have not enough definition for a 2.35 PAL DVD.
     
  4. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    You are assuming that all the picture information on the disc is used for programme material. Remember that with a 2.35:1 around a 1/3rd of the info on the disc is black bars. So the actual encoded resolution of the picture is not 576lines.

    Anyway.....more pixels is better.


    Gordon
     
  5. SimonInd

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    You're not quite right, the 2.35:1 refers to the aspect ratio of the film, on an anamorphic DVD this will be presented as the middle 435 lines with black lines above and below making up the 576. The full DVD frame is still 1024x576, it's just that it's not all used by the picture.

    Regardless of all this, with some capable scaling a 1280x720 projector should always give you a better picture than a comparable 1024x576 one.

    Cheers

    Simon
     
  6. RTFM

    RTFM
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    It's got nothing to do with the aspect ratio of the film but the output of the PAL DVD player which is indeed 576 lines.
    You can't exploit the whole Matterhorn or Mustang chips with 2.35 films unless you employ an Anamorphic lens.
    There are some informative posts on the AVSForum by Alan Gouger regarding utilising the whole panel and adding an Anamorphic lens.
    Gary Lightfoot does a similar thing with his NEC HT1000 by using the 1024x768 chip and squeezing the image from 4:3 down to 16:9.

    Jeff :rtfm:
     
  7. stauDLP

    stauDLP
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    Thanks to all,
    so you're saying:

    1) no lost of information, for the PAL 2.35 dvds use only 435 lines.

    2) 435 lines are the ones used from the 1024x576 projectors too, so no scaling in this case

    3) when using a 1280x720 projector: 435(dvd) to 544(projector) lines we have scaling (let's hope good)

    4) if you want to exploit the chip in 2.35, buy a 650€ lens (does it worth?)

    My question now is:
    why the 2.35 dvd is only 435 lines?

    Wasn't it just a question of lenses used during the acquisition from original cinema's film? It shouldn't imply a bigger amount of data, but just a matter of right rescaling, isn't it?
     
  8. Beastie Boy

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    All PAL DVDs have a resolution of 720x576.

    There is a flag encoded into the MPEG2 stream which tells the player whether or not the source is 4:3 or 16:9 aspect ratio, and this would then be played back as 768x576 or 1024x576 pixels respectively (on a digital display).

    1:2.35 DVDs are actually 16:9 ratio with part of the picture frame effectively blanked with black bars. So, a 1024x576 projector would match the resoluton perfectly with no scaling.

    As already stated, a good scaler would produce a better looking image on a 1280x720 display. That is why HCPCs are popular as DVD plyers as they perform fantastic scaling and can also apply a degree of sharpening to really make the image 'pop'.

    Cheers, Beastie.
     
  9. RTFM

    RTFM
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    Wasn't it just a question of lenses used during the acquisition from original cinema's film? It shouldn't imply a bigger amount of data, but just a matter of right rescaling, isn't it?[/QUOTE]

    It's got more to do than with the lenses used to shoot the original footage.
    Here are some of the different photographic systems used for film production.

    35mm camera, 4 perforation pull-down, spherical lens (non-squeezed) photography

    35mm camera, 4 perforation pull-down, 2:1 anamorphic lens (squeezed) photography (Panavision 35 and Todd-AO 35)

    35mm camera, 2 perforation pull-down, spherical lens (non-squeezed) photography for 4 perforation anamorphic (2:1 squeeze ratio) release prints (Techniscope)

    65mm camera,5 perforation pull-down, spherical lens (non squeezed) photography (Todd0AO and Super Panavision)

    65mm camera, 5 perforation pull-down, anamorphic (1.25:1 squeeze ratio) photography (Ultra Panavision)

    Roll on Hi Def DVDs authored from movies shot on 65mm Super Panavision cameras :smashin:

    Jeff :rtfm:
     
  10. Beastie Boy

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    The original question was more to do with the resolution of 1:2.35 AR DVDs. Regardless of the content, the source video encoded on the disc is fixed at 576 lines. Nothing can change this. If the source FILM has an AR of 1:2.35 (note that this AR is not fixed and 1:2.5 is also common) then only 436 lines will contain picture info, but the rest are there nonetheless. The black bars are actually encoded into the video as part of each frame and thus take up some of those 576 lines.

    Buying a projector with a higher resolution will not reveal more information from the disc as a 1024x576 chip alredy has enough pixels to show every pixel on the DVD.
    A higher res chip may simply make the image look a little better on a large screen, but no more detail can ever been shown as it simply does not exist on the disc.

    Cheers, Beastie.
     
  11. rpjcheney

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    Hi Jeff,

    Am I right in thinking that using anamorphic lenses only relates to 4:3 display units when showing widescreen (1:1.85, 1:2.35)? From what I understand, it allows it to show it naturally widescreen (using full resolution and therefore detail / lumens) in the same way that a widescreen CRT TV stretches out anamorphic widescreen DVDs? (i.e. 16:9 squeezed into 4:3)

    Or are you instead talking about vertical anamorphic lenses of some sort, for 2:35 use only?

    Simply curious!!

    Regards,

    Rich.
     
  12. GliderRider

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    Ok, can we step back a bit. I'm new to this and should receive my DLP 1280X720 early next week. Forgetting numbers for now, I'm trying to gain an understanding by making a comparison. I have a 16.9 TV. When I play DVD's some play with small black bar top and bottom and some of the really panoramic movies (e.g. 1492 Conquest of Paradise) give a real letterbox and a large black bar top and bottom. This prompted me to buy the PJ because I did not want to lose the sides of the movie just to fill the screen but got fed up trying to watch a thiin strip of movie. My understanding is that with a native 16:9 Projector the same thing will happen, but with such a large image the "letterbox" size will be cool. Have I got this right or does the PJ do something magical? If the PJ gives me a viewing area of 16:9 for the above movie then surely I'm losing the sides again? If Ive got this wrong then please explain without too many numbers.
     
  13. rpjcheney

    rpjcheney
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    No, sounds like you have got a handle on it.

    It will display just like your widescreen television, but it will be so big that you won't mind!
     
  14. Gary Lightfoot

    Gary Lightfoot
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    Hi,

    Jeff hit the nail on the head earlier when he mentioned using an anamorphic lens:

    Send the projector an unsquished 2.35:1 movie, so that it fills the 16:9 area of the display - use a display option on the pj so that you can do this (if possible). If the pj doesn't allow it, the player might (some have an 'anamorphic' setting which does this)An HTPC with something like Zoom Player will allow this with relative ease.

    Now, you will have tall skinny people etc filling your screen, and in order to get the image back to the correct ratio, you add an anamorphic lens. In doing this you've used all available resolution for the image, and none (or very few, depending on how it actualy looks when 'unsquished') for black bars. The black bars that you will have left will not contain any light from the projector either, so you not only gain better resolution, but also no light spill, so blacker bars on screen.

    HTH

    Gary.
     
  15. stauDLP

    stauDLP
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    Dear Beastie,
    so you're saying that in the acquisition we are forced to use only 436 lines.

    1) Why is not possible to acquire 576 lines and use a flag saying to rescale the horizontal dimension to the appropriate number of pixel?

    2)If only 436 lines are used, do we have more Gbyte we can use for a better mpeg2 compression?
     
  16. Gary Lightfoot

    Gary Lightfoot
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    All 576 lines are used for a 2.35:1 movie, but only 436 of them contain the image, and the rest are black bars. For a 16:9 image, all 576 lines contain image, and with no black bars.

    Both are encoded onto the disk in exactly the same way, the only difference is that one contains black bars and the other doesn't - the black bars are encoded as part of the 2.35:1 image to make it fill 576 lines and it is treated in exactly the same way as a 16:9 image when displayed.

    Gary.
     
  17. stauDLP

    stauDLP
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    OK, thanks!
    Now so clear!
    So let assume we use the same mp2 algorithm to compress the same film in 16/9 and 2.35
    I assume in 2.35 we will save Gbyte ( no data amount for the black bars). Is the same thing when you decide to get div-x from dvd and decide for a bigger/smaller format, isn't it?
     
  18. Gary Lightfoot

    Gary Lightfoot
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    I guess you would save some data for 2.35:1 as the black bars would take up very little room. That might use the extra data to increase the bit rate for the rest of the image though, so depending on the authoring process and who's doing it, you may or may not see a gain in some form or another.

    Gary.
     

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