1. Join Now

    AVForums.com uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

CRT is no longer the contrast king

Discussion in 'Projectors, Screens & Video Processors' started by Welwynnick, Aug 26, 2005.

  1. Welwynnick

    Welwynnick
    Well-known Member

    Joined:
    Mar 16, 2005
    Messages:
    7,084
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    133
    Location:
    Welwyn, Herts
    Ratings:
    +825
    Do you know, when I dared to suggest on another forum that the yardstick for video reproduction was the 9" CRT, I was met with a deafening silence, because nobody knew what I was talking about! Some consumers don't seem to realise that there is a World beyond Tesco and Currys.

    Anyway, I'm afraid what I said may not be true any more. People have been predicting SED as the next big thing for a year or so, but the pace seems to be accelerating. Canon and Toshiba appear to have commenced pre-production of 50" 1080p SED panels, and all the ingredients seem to be there to take over the market, and they forecast the imminent demise of CRT.

    http://answers.google.com/answers/threadview?id=525928

    Those sorts of things have been said before, of course, and whenever there is a debate about display technologies, it always seems to come full circle on the CRT advantage with blacks. Digitals have their advantages, but they can't do black.

    Well, they can now. Prototype SED panels measured a dark room contrast of about 8700:1. Quite good, you might think, but not really enough to beat good old CRT. Well, it seems they have been burning the midnight oil to realise the full potential of SED. The newest panels are reported to measure a contrast ratio of - count the zeros - 100000:1.

    Tick tock, tick tock....

    Nick
     
  2. JimmytheSaint

    JimmytheSaint
    Active Member

    Joined:
    Mar 21, 2003
    Messages:
    1,741
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    51
    Location:
    London
    Ratings:
    +97
    Nick, isn't SED based on a miniture version of the technology behind CRT, hence black levels match CRT levels?
     
  3. Welwynnick

    Welwynnick
    Well-known Member

    Joined:
    Mar 16, 2005
    Messages:
    7,084
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    133
    Location:
    Welwyn, Herts
    Ratings:
    +825
    Yes, in principle it's like having millions of tiny CRTs in a big flat panel. Just without any beam steering.

    That's probably doing it a disservice, though, because of the novel technology behind the cathodes, and the significantly improved brightness, blackness, cost and electrical efficiency.
     
  4. NicolasB

    NicolasB
    Well-known Member

    Joined:
    Oct 3, 2002
    Messages:
    6,036
    Products Owned:
    1
    Products Wanted:
    0
    Trophy Points:
    136
    Location:
    Emily's Shop
    Ratings:
    +660
    SED is a sort of fixed-pixel version of CRT.

    CRT, plasma, and SED screens all produce light by using phosphors - chemicals that glow when excited by some high-energy method.

    In a plasma screen the phosphors are excited by ultra-violet light generated by passing an electrical current through an ionised gas (plasma).

    In a CRT the phosphors are excited by a single electron beam that is scanned across the screen. (Well, I say "single" - there are 3 electron beams in a typical CRT set, one for the red phosphor dots, one for green, one for blue). In a CRT display there is no single physical structure corresponding to a pixel. Things are alligned in such a way that the "red" electron gun can only fire electrons at red phosphor dots, and intensity of the beam is varied as it scans across the surface. One "pixel" is probably several phosphor dots wide.

    SED works by having a very large number of electron emitters right next to the screen - it's a bit like having one tiny electron gun for each subpixel. This means that it's a fixed-pixel display, like plasma, or LCD or DLP: each image pixel has a corresponding physical structure. But you get contrast ratios that are as good as or better than CRT, combined with the high resolution and thin, flat screens that you'd have with plasma or LCD.

    Like any phosphor-based device it will still be subject to screen burn, though.

    And not being a fixed-pixel display does give CRT some advantages if you want to use more than one display resolution (e.g. 720p and 1080i). A fixed-pixel device would have to be optimised for one or the other (or, as is usually the case, optimised for another resolution which is completely useless, such as 1366x768).
     
  5. crteaman

    crteaman
    Active Member

    Joined:
    May 18, 2004
    Messages:
    420
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    21
    Ratings:
    +6
    100000:1 yada yada yada


    James
     
  6. Nic Rhodes

    Nic Rhodes
    Well-known Member

    Joined:
    Mar 23, 2001
    Messages:
    17,133
    Products Owned:
    0
    Products Wanted:
    1
    Trophy Points:
    133
    Location:
    Cumbria
    Ratings:
    +1,277
    I am a fan of this technology but how the hell do you measure 100000, something smells fishy to me :)
     
  7. Welwynnick

    Welwynnick
    Well-known Member

    Joined:
    Mar 16, 2005
    Messages:
    7,084
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    133
    Location:
    Welwyn, Herts
    Ratings:
    +825
    Well, they quoted some some measured foot-lamberts figures, can't remember what they were, but the black was 99.999% darker than the white.

    Nick
     
  8. Gary Lightfoot

    Gary Lightfoot
    Distinguished Member

    Joined:
    Apr 6, 2001
    Messages:
    12,418
    Products Owned:
    1
    Products Wanted:
    1
    Trophy Points:
    166
    Location:
    Surrey. UK.
    Ratings:
    +2,083
    Hi Nic,

    It's difficult to measure the black if it is too dark because there is insufficient energy for a light meter to read it. At that point you can invent any value you like like 50,000:1 or 100,000:1 as it becomes meaningless.

    Calibrated CR is and how well it can display shadow detail is more impoortant. CRT owners can achieve infinity CR if you wish by turning down the brightnes so no light exists at black, and then any white level will give you infinity CR since any number divided by zero is infinity.

    If you raise the black level so that details are visible, then you will get some light output at black, and a good way to ensure the display is showing black correctly is to us a test disk like Avia or DVE. That way when black is being transmitted to the display (0v for PAL, 53mv for NTSC), it will be correctly displayed and hopefully with a good amount of detail at the levels above.

    If CED works much the same way as CRT then I don't see why similar calibrated CR of around 10,000:1 won't be the norm, but with ANSI contrast that matches or betters DLP since there will be no lenses for light scatter to occur in. That's just a guess on my part though. It could be the ultimate display if it can produce even colour and white across it.

    Gary.
     
  9. Nic Rhodes

    Nic Rhodes
    Well-known Member

    Joined:
    Mar 23, 2001
    Messages:
    17,133
    Products Owned:
    0
    Products Wanted:
    1
    Trophy Points:
    133
    Location:
    Cumbria
    Ratings:
    +1,277
    exactly my worry Gary.
     

Share This Page

Loading...