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Contrast Ratios

Discussion in 'LCD & LED LCD TVs' started by scrapbook, Mar 29, 2005.

  1. scrapbook

    scrapbook
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    I appreciate that these are often measured in different ways by different manufacturers, but I can't help but feeling disappointed that the newer panels being mentioned of being released over the next few months are only quoting figures of 800:1.

    In theory is there a limit to the contrast ratio available with this technology? The latest plasmas quote figures of 4000:1

    I saw a top of the range 37inch LCD at the Ideal home exhibition show at the weekend showing Gladiator and could help but notice in some of the dark scenes areas just become one big splurge of black. I would have expected more from a sharp panel, although to be fair I didn't check to see how it was connected. It was interesting in that all the over panels were showing Monsters Inc etc as normal!
     
  2. MokerJoker

    MokerJoker
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    Don't believe the manufacturer's figures. LG upped their Contrast Ratio from 1200:1 to 5000:1 just by changing the way they measured it. In independent tests, the CR of LCD's and plasma does not differ that much. In fact, many LCD's perform better than plasmas. Still, Panasonic and LG plasmas score the highest CRs.

    CR does not say anything about the details in dark areas. 'Black crush' (lack of detail in dark areas) is a common problem of LCDs and some plasmas. Tweaking CR and brightness can improve the detail in dark areas.
     
  3. ianh64

    ianh64
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    You only need a 256:1 contrast ratio to theorectically get a perfect grey scale on a LCD. Higher figures will only give you blacker blacks and/or whiter whites. You could put a lighthouse bulb behind an LCD panel and get a huge contrast ratio, but it still wouldn't mean that you would get black blacks.

    I bet that LCD panel at the ideal home show was not ISF calibrated. It would be the only way to know for sure how it stacks up to a 4000:1 plasma that has been also calibrated. I would bet it wasn't as much as the figures would have you believe, thats if the winner was indeed the plasma, it may not be.
     
  4. LcdGuru

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    Not really. Ideally the blacks should be absolutely black, (zero reflection and zero emission) in which case the contrast ratio would be infinity.

    In my experience LCDs generally have a lower reflectivity than Plasmas due to ambient light absorption by the LCD RGB colour filters - giving LCDs a better contrast ratio in a well-lit room.

    However plasma's have a better CR in a darkened room - due to LCD light leakage on black.

    Set against that, plasma's typically have only 10-bit greyscale rendition - so you get some quantisation and contouring in dark areas of the picture - whereas LCDs have an analogue greyscale so they have perfect black detail - with no contouring.

    Of course - all these observations assume you have a well setup LCD or Plasma: which is often not the case.
     

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