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CRT resolutions

Discussion in 'Projectors, Screens & Video Processors' started by cosaw, Jun 21, 2003.

  1. cosaw

    cosaw
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    Hi

    I'm new to CRTs and a have a question about resolutions.

    In passing I read another thread and Roland said in relation to the Barco 801s:

    "Aim to run your PC at 800x600 for the 16x9 mode 1024x768 for 4x3."

    Can you explain to me Roland or anyone else: With regard to widescreen playback and DVD. The max res of a PAL dvd is 720x576. Can this max resolution be viewed at 800x600 on a CRT? I know on my PC with a 4:3 screen ratio this is not possible, yes all the image will fit but this is before the anamorphic image is stretched horizontally by which time the image would be off the screen if power DVD didn't compensate by scaling to screen size by interpolating (or whatever the software does) some of the horizontal lines of resolution. If I move up to a res like 1152x864 then mathematically all the image data should be able to be seen. You can see the picture quality is better cos all aliasing is removed.

    Do the CRTpjs handle it differently? I don't want to look at a great big image if I'm not seeing the whole res and can see aliasing. It would seem that the native res of a CRT would be more similar to a 4:3 ratio due to the square phosphor area?

    Thanks all

    cosaw
     
  2. Stuart Wright

    Stuart Wright
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    I would say that most CRT owners use them set up for 16:9 and use 16:9 screens.
    Most people also watch NTSC rather than PAL because NTSC DVDs are generally better and/or available earlier.
    Roland was referring to using a lower resolution if you are using an anamorphic setup because the lines are squeezed closer together and at around 600 horizontal lines, you won't have a problem with them overlapping (which causes a softer picture). At 4:3, the lines are further apart so you can use a higher resolution without softening the image.
    Use software like Powerstrip to create custom resolutions (provided your graphics card supports them).
    It's the number of horizontal lines which is important.
    PCs do a brilliant job of interpolating the output of a DVD to whatever resolution you are using and this is why they are so popular. However people try to use multiples of the native resolution wherever possible because this in theory (and probably in practise) makes it an easier job.
    600 is 2.5 times 240 which is the interlaced resolution of NTSC DVDs (I think I recall).
    If you haven't tried the resolutions then get Powerstrip installed and try them on your monitor. I think you'll be impressed by the quality.
     
  3. cosaw

    cosaw
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    Thanks for the info, I'll have a look into power strip.

    You say: "Most people also watch NTSC rather than PAL because NTSC DVDs are generally better and/or available earlier."

    I always thought PAL was the higher quality standard with higher resolution? Do you mean NTSC releases better in terms of the extras? Personally I am only really interested in the film itself and am prepared to wait the extra time for a PAL release.

    I understand what you mean about the lines being squeezed closer together, what I'm saying is pottentially this could still hapen if your using a 4:3 shape resolution of 800x600, what I mean is this (roughly, numbers and shapes don't quite add up):

    Diagram 1: Display area at 800x600:

    1 2 3 4 5 6 7 8
    2 * * * * * * *
    3 * * * * * * *
    4 * * * * * * *
    5 * * * * * * *
    6 * * * * * * *

    Diagram 2: PAL DVD resolution 720x576 aspect ratio not corrected (picture and people appear tall) image:

    1 2 3 4 5 6 7
    2 * * * * * *
    3 * * * * * *
    4 * * * * * *
    5 * * * * * *

    As you can see diagram 2 fits into diagram 1, the complete horizontal and vertical res are displayable.

    Diagram 3: PAL DVD, stretched<> or squeezed^ (whatever is needed to get 16:9) viewable image:

    < stretch >
    1 * * * * * * *
    2 * * * * * * *
    3 * * * * * * *
    4 * * * * * * *^ squeeze or removal of lines (I don't know?)


    See how now dia 3 won't fit into dia 2, its too wide, so you can't stretch wider than the displayable area, result: need to stretch only to full screen width and horizontal lines will still have to be squeezed together, removed or interpolated.

    What I'm saying is at a res of 1152x864 (and perhaps 1024x768, I haven't worked it out) you can stretch<> without having to squeeze^ and therfore can display the total resolution of the dvd.

    I know you state that: "It's the number of horizontal lines which is important." But I'm sure I've read that: the results you get out are only as good as the data you put in. Surely then a higher res would be more ideal as you can maintain the total original data. i.e. you don't have to start with lesser material and then scale from there.

    Also what do you mean by: "if you are using an anamorphic setup"

    Sounds like your suggesting that CRTpjs have some sort of anamorpic mode? Is there something like a widescreen 800x600 with stretched horizontal pixels? If so I suppose this would clear everything up?

    These may be tiresome questions to the experienced but this novice would be grateful for any help!!

    Thanks again

    cosaw
     
  4. cosaw

    cosaw
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    Sorry let me correct myself on the above:

    Diagram 3 should appear wider than diagram 1.

    And just after diagram 3 I should have said: See how dia 3 won't fit into dia 1 (not: "into dia 2")

    cosaw
     
  5. Caveat

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    The good news is that there is something exactly "like a widescreen 800x600 with stretched horizontal pixels".

    CRTs dont have a "native resolution" in the same way as digital projectors do, so the pixels dont have to be "square" and its very common in htpc's to project a 4x3 pixel image at a 16x9 screen - as you say exactly whats needed to re-strecth anomorphic images back into shape.

    I use an htpc at 800x600, but this projects onto a 16x9 screen - just set the vertical and horizontal size on the proj appropriately.
    This means that a circle on my desktop looks oval but an anamorphic DVD shown full screen is re-stretched back to the right AR. If you find the scaling gives noticable artifacts you can set the htpc to output 720x576 @ 50Hz explicitly (using powerstrip) and again simply use the proj v and h size to fill the screen.
    Less than 600 pixels height makes using windows pretty tricky, you find the OK and Cancel buttons are off the bottom of the screen.

    Ive recently been playing with a DTTV card which seems not to be able to understand Im using a 16x9 screen (perhaps because of the 4x3 res), so Ive set up another memory block on the projector that keeps the vertical size but squeezes the horizontal size to give a 4x3 projected image (full height but "Pillar Boxed" on my screen). The TV image probably benefits from the smaller size anyway.
    The ability to stretch the image like this without sacrificing resolution (even if you lose a little brightness with less phosphur) is quite an appeal of CRT.
     
  6. cosaw

    cosaw
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    That's great News. These CRTs are obviously pretty clever things. It's difficult to know all the ins and outs without having one as you can probably appreciate. Just trying to build my knowledge up, we've got a Sony 32" telly at the moment which I want to incorporate: I'll probably build my HTPC and get a modest sound system rigged, sort out any problems and then go for the CRT.

    I can probably then get some practice with things like powerstrip on the telly. Our particular sony model (KV32DX40) still compromises on the full widescreen picture. When fed dvd through sony dvd player, 2.35:1 ratio films come out letterboxed but not by the full amount, the image you see is around 1.85:1. 1.85:1 films come out full screen 16:9, whereas really these should still be letterboxed. Its not the dvd source that's the problem cos the telly still dose the same thing withVHS starwars widescreen which comes out correctly on a 4:3 telly. After buying the telly and researching this disapointment I found that you'd have to pay an extra grand if you wanted the model with panoramic mode, or whatever they name it, which did things properly. There's a cheaper panasonic that does it as standard but the picture quality is nowhere near as nice IMO. An HTPC with powerstrip would allow me to pre-format the picture dimensions before sending it to my telly (wich unsqueezes everything by the same amount in "wide" mode) and thus achieve the total and correct aspect ratio.

    As you can see I hate buying products which can't actually do what I reasonably expect of them!! Anyway thanks for furthering my knowledge on this one, I appreciate it!!!

    Cosaw
     

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