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Response time and Picture Quality

Discussion in 'LCD & LED LCD TVs' started by Ramspeed, Jun 15, 2005.

  1. Ramspeed

    Ramspeed
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    Hi there

    Aside from matters of personal taste (colour, tone, contrast) the greatest criticism levelled at LCD TV's is motion blur and smearing. Is this down to the response time of the panel? Given a hi def feed (or RGB DVD as a minimum) should any LCD with a response time of 12 ms or less be more or less free of smearing and motion blur?

    I ask because come this autumn I'm going to get me an LCD for my XBox 360 (which outputs at 720p as standard) and I'm trying slowly to work out what i should be looking for in a display...

    Thanks.
     
  2. alefsin

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    You should not worry that much about the response time. Modern LCD screens in the "big" TVs (like 32") are in fact a bit faster than the best 17" LCD monitors you use with your computer. Why? Apparantly this has to do with much larger size of the pixel elements. In some reviews (like that in the tom's hardware review) the reviewers where quite surprized and amazed with the fast response times of all 32" LCDs they tested.
    You may yet see some smeering or other problems on a LCD but it is mostly because of the deinterlacing process not the response time. The better LCDs use advanced deinterlacing methods and are practically perfect but the cheaper models can have some problems. Try to watch a news channel with moving banners in shop with different screens to see what I mean. My Hitachi 32LD7200 is certainly better than my old CRT in this respect.
    Personally, what I'd like to see getting improved in the big LCDs is the black level which can be very poor even in the best LCDs. For example, the black level on Tosh 32WL48p is up to 10 times worse (== higher) than a top class 17" LCD monitor!
     
  3. Ramspeed

    Ramspeed
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    thanks alfesin

    If i understand you correctly it's interlaced signals that LCDs struggle with. In which case do the smearing and motion blur problems go away when you're using a progressive scan signal i.e. 480p/720p etc. ?
     
  4. David Mackenzie

    David Mackenzie
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    Smearing and motion blur are typically caused by the panel, so they'll appear no matter what the source. If the panel isn't rated for a high enough speed, you'll see the problems.

    Handling of interlaced signals is a different matter. The TV has to deinterlace them so they can be shown without motion artifacts. Basically 50fps pictures are sent over the air with the information of what would originally be two individual pictures, crammed into one:

    [​IMG]

    The LCD TV then has to use that one interlaced frame to create two frames and reconstruct the original 50fps picture. Of course, deinterlacing, especially done on the fly, is never perfect and some odd patterns can appear (on fast moving horizontally scrolling credits, for example). This COULD look like smearing/blurring but once you've used an LCD TV for awhile you'll probably be able to tell what's being caused by the panel and what's being caused by the image processing.

    Smearing by the panel is becoming less and less common, so much so that it's barely a problem any more.
     
  5. Digitised

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    id just like to add a few things,

    response times arent generally accurate anyway, whats given in the standard ms time is just the time it takes for a white pixel to black out and return to white.
    All LCD screens are based on white created by the bulb in the unit.
    This gives LCDs their brilliant bright colours.

    Each pixel is made of subpixels (green blue red) which can be stimulated electrically to twist. When they twist the colours become thick and the white light that shines through them becomes filtered to whatever degree of colour. (eg red and blue = purple)

    Anyway when it comes to the measuring, tests only measure the transition of -
    white, to black, to white.
    Since this is the standard test for producing 'official' response times there is obviously going to be optimisation on behalf of companies competing to get the lowest.
    When LCDs switch 'other' colours on and off, they tend to be slower.
    Tests have shown 8ms tft panels to be excellent with white and black, getting 7-9ms in independant tests.
    Whereas the same panels have been awful with browns, reds, greys ending up in the 30ms range.
    To me this screams optimisation since the 'real world' average pushes the response time to 20ms on average.
    The fact is 25ms panels can be better than 10ms panels, it all depends how well they handle the other 16.7 million colours.


    The good news is blur in LCD screens is far less noticable in hi resolutions.
    Ive set my philips 9986 up to my pc, and ive been running it in 1024x768. 80% of the motion problems ive had with consoles has disapeared, a lot being interlacing and poor frame rates.
    Its only noticable up close, and even then its more than forgivable. You have to make it happen in most cases for eg. playing a game, and looking at a dark object on a light background, and then shifting your view to make it smear...
     
  6. Digitised

    Digitised
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    sorry to double post...


    xbox 360 is going to be all analogue!!
    no hdmi or dvi support!!

    it was announced component at best, and its too late now for them to make alterations to inputs. Its a shame because its such a simple cheap process to fit a dvi port (even cheap g-cards have them).

    If i were you, id hold on till they release a 1080p display.
    PS3 is going to be HDMI, and will support pictures that even todays TVs cannot muster.

    I dont even think 1080p tvs even exist yet, but the PS3 is a good reason to wait for one. If you cant wait however, check out the philips 9830 models which are out soon.
    If they manage to surpass the 9986 then you will be a very happy owner.
     
  7. matt_p

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    I had heard that they will be starting with component as standard, but if there is demand they will add HDMI later. The AV output on the back will be proprietary as with the current xbox, so they can create whatever connections they want and fleece you on the cables.

    Had a link somewhere...
     
  8. alefsin

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    While you are right about the values that the OEMs report in their product sheets, the fact is the response time CAN be measured accurately. I like Tom's Hardware reviews because they actually measure the response time very accurately and don't just simply give you a number, but provide you a graph of the response time for transitions between all gray levels. Also they use a colorimetry based method (again with graphs, not single numerical results) to evaluate the color fidelity of the screens. Based on their measurements, 32" LCD screens normally have excellent response time but unfortunately very poor black leveles and color fidelity. They have not tested 9986 but they have 32WL48P in their tests.
     
  9. Nick_UK

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    TV pictures are made up of 25 frames, or 50 fields per second. So each field is refreshed every 20mS. If an LCD has a refresh time of 20mS or less, you should not have a problem with smearing. Note that this applies to TV sources only - PC's and gaming machines have higher frame rates !
     
  10. serial45

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    There is strong rumour that there will be a later version of the xbox 360 with blue-ray, in fact its almost certain (trust me I have my sources).
    Games of course will all be on DVD-R, they wont start undercutting the current xbox 360 owners.
    So this is bound to be dv-i / hdmi!
     
  11. NicolasB

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    Bluray and not HDDVD?
     
  12. pjskel

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    Given the recent announcement of Samsung getting into Xbox's bed with their displays, you can be there will be DVI/HDMI connectivity.
    I fully expect the HW to be fully revealed by late August or mid September, with November release date.
     
  13. David Mackenzie

    David Mackenzie
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    I think Microsoft are going with HD-DVD and plan to offer it as an upgrade. Ouch. A bit messy for a console, no?
     
  14. scrapbook

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    Errrr you don't have the best sources if they are telling you the 360 is going to come with blue-ray drive at some time. :eek:
     

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