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Black levels...

Discussion in 'LCD & LED LCD TVs' started by neurotoxicity, Jul 17, 2005.

  1. neurotoxicity

    neurotoxicity
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    Hi All,

    I have recently returned a LG RZ32LZ50 to the shop after a couple of days of use because the blacks it displayed simply were not black enough and the whites seemed to burn out far too easily!

    In looking into these things a bit closer, it seems as if *all* LCDs suffer this problem to some extent. I'm wondering if the higher quality sets I've been reading about (either the Philips 32PF9986 or the Panasonic TX32LXD500) would have similar problems?
    My initial budget was around £1000, but it seems as if I'm going to have to go way over that - or is there a cheaper option that I'm missing somewhere that'll satisfy my need for inky-inky-blacks?

    Or could it be I'm just too picky... ;-)
     
  2. braveknight

    braveknight
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    It's well known that LCDs won't produce blacks that are as deep as some other display types. But then current LCDs do produce blacks that easily beat front projection systems (ie. cinemas), and even older CRTs.

    There is also a problem with inky blacks - try finding a display that produces them that doesn't use a lot of glass, the end result being the potential for a lot of reflections. It's a personal thing, but I find reflections far more disturbing than how deep the black is.
     
  3. Llanowar

    Llanowar
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    Same here as braveknight, my blacks on the jvc aren't grey, but it's not inky black at all, reducing the backlight does well, and higher sources give better blacks as well! I don't care much about it, the reflections on my crt and plasma irritated the hell out of me. Now i can just watch the tour du france during the day!!
     
  4. neurotoxicity

    neurotoxicity
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    I guess the problem that I face is that I want to be watching films such as Dark City, Aliens, etc. Mostly during the evening or night.
    The question really is whether or not the LG screen was a good example of black levels in the LCD field at the moment? The reviews (for what they're worth), of the other couple I mention, seem to say that the darkness really isn't a problem on them.

    Just a shame that Sony can't bring out the XBlack LCD screens for TV use... Though I dread to think what they'd charge!
     
  5. David Mackenzie

    David Mackenzie
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    Do you own an Xblack screen or are you going from what you've seen in a store?
    My brother bought one of these and when we got it home, the black level performance wasn't any better than other new LCD monitors - we thought Xblack was just a marketing idea, but we could be wrong.

    What do you mean by black level also - do you mean the unappealing glow given off by the backlight, or do you mean the TV's ability to reproduce all the detail present in dark areas?
     
  6. neurotoxicity

    neurotoxicity
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    Just what I've seen in the shop and the various reviews that are around; I thought it looked very impressive. That said, I know that lots of things look impressive until you get 'em home!

    By black level, I was really thinking about the inability to show the detail in the dark areas. It seems as if the LG got down to a certain level of darkness then gave up - showing everything as the same shade of near-black.

    I presume that, given time, my eyes would get used to the near-black; but I think that actually missing detail is a bit less forgivable...
     
  7. David Mackenzie

    David Mackenzie
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    That's my feeling too, I find the backlight glow a bit distracting sometimes but it makes me feel better that I'd see similar mistyness when I go to watch movies at the cinema. Like you, the missing detail (down to contrast ratio, I believe) is what would concern me more.
     
  8. braveknight

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    Contrast ratio isn't really anything to do with it - it's just a measure of the difference of light output, you could have a gigantic contrast ratio on a screen that is only capable of displaying black and white, but with nothing in between, there is no detail!

    Three factors have a more direct relationship to detail. Number of colours/shades that the screen can represent - although it isn't always the case that more shades gives you more visible detail. We need a certain amount of difference between two shades, otherwise we see them as the same. LCDs resolve enough shades to have good detail.

    Processing can also have an effect. The LG I believe has 8-bit processing, and could possibly lose some detail with some of the processing (although 8-bit is sufficient to represent enough detail, but you may have a number of cumulative errors in the processing). The latest Samsung (and others?) use 10-bit processing, which gives more headroom.

    (another point on processing - the LG may have some form of contrast enhancer as part of the XD engine that could crush the details. Samsung's dynamic contrast can certainly crush details, but you do get to turn it off!)

    Lastly, the settings on the panel may just be wrong. You may have fallen into the trap of having brightness too low in pursuit of blacker blacks, and just losing all the detail by making it 'blacker than black'. I think you've got to accept that black isn't necessarily as black as you think it should be and raise that brightness to retain the low-level detail (and possibly lower contrast so that you don't crush the whites).
     
  9. msg

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    I've recently purchased Panasonic 50 series LCD and was concerned by greyness of blacks as ambient light fell away late in the evening. But, reading this thread, this seems normal for LCDs and is the effect of the backlight 'breaking through'. Not sure whether the Panasonic is better than others in this respect - comments welcomed.....

    I've got the CATS sensor active (ambient light sensor) in the hope that this drops backlight brightness at night. However, it's either not working or very subtle (putting my finger over the sensor seems to have no effect).

    Anyone know whether the CATS sensor on the Panasonic 50 & 500 series LCDs reduces backilght intensity, or just contrast and brightness?

    In the meantime, pictures during daylight on this TV are remarkable; shame about the greyness of blacks at night.

    Dave

    ;)
     
  10. David Mackenzie

    David Mackenzie
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    Thanks for clearing that up, braveknight. I assume the (number)-bit processing's referring to with what level of preciseness the images are digitized?
     
  11. ianh64

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    You don't buy the current crop of LCD screens for watching dark films in a dark environment - you are right, there are better technologies for this. But in a lit environment, the depth of black of an LCD with no reflections, when compared to a CRT or plasma that may be struggling with reflections is a contest that the LCD may even win.

    However, the dynamic range of blacks, or lack of is a completely different story. Straight out of the box, you should be able to dramatically improve on this by tweaking the brightness and contrast. Using a test disc like DVE makes this easier but it will still not be perfect unless you know exactly what controls (normally hidden in the service menu) how to correctly set the grey scale. A ISF calibration whould however get this as perfect as can be - I suspect, not as good as an ISF calibrated CRT, but probably much better than a non ISF calibrated display of any technology. FWIW, ISF calibration would set you back about £250 and if you are serious about the quality of one display compared to the quality of another, it should be factored into any purchase.

    -Ian
     
  12. braveknight

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    Yes, it refers to the number of shades that can be represented. 8-bit gives you a 256 shade grayscale (and 16.7million colours total), 10-bit gives you a 1024 shade grayscale (and billions of colours).

    256 shades of gray should be enough to stop the eye from distinguishing one shade of gray distinctly from it's neighbour, therefore allowing (with enough resolution) a perferctly smooth transition. However, if you are processing the image precise calculations would give you a value that falls between the shades, and needs to be truncated or rounded to the nearest value that can be represented - an 'error'. The more shades of gray you have available, the fewer / smaller errors you have in processing.
     
  13. neurotoxicity

    neurotoxicity
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    I think that has pretty much sorted out where I am coming from. Guess it's time to head over to the Plasma forums ;-)

    One article on this topic I have found interesting though is here: ExtremeTech
     
  14. ianh64

    ianh64
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    The extremetech article was published in Wdescreen Review magazine and some of it was out of date at the time of publication. The web date is Jan 2005 and I am pretty sure that WSR had published or started publishing well before that.

    What I am trying to say is, it is an excellent article, but out of date already. I believe that the NEC LCD4000 is atleast a generation old - or at the very least, does not match up to the decent panels from the last year - for example it has a response time of 23ms - we are down to sub 12ms now.

    Often buying a display is a compromise and no technology is perfect. But knowing whether a technologies faults will affect your viewing requirements is a handy piece of information and something that can be checked to see whether it aflicts newer generations of the same technology. The problem with black level may soon change as some manufacturers have announced products that are designed to help.

    -Ian
     

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