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Are there any good rear projection CRTs?

Discussion in 'Projectors, Screens & Video Processors' started by Welwynnick, Jun 30, 2005.

  1. Welwynnick

    Welwynnick
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    Browsing around one of the big high street stores the other day, I was looking at the LCD and DLP rear projection sets, but didn't stop long for obvious reasons. However, a couple of nearly forgotten CRT rear pro sets caught my eye. The pictures looked rotten because everything was fed by composite, but the dynamic range of these things was spectacular - black was black, in er.. contrast to everything else.

    This got me thinking. I was able to see real(ish) black in large screen images in a shop with enough light for people to see their way around. I don't know much about CRT rear pros, and they sure seem to be dying out, but it occurred they just might make sense. If they have three tubes, then the images won't necessarily be constrained by lines and pixels in the usual way. And maybe in day to day viewing they can show good contrast when there is light in the room.

    Can anyone say if there are any really good ones? Most seem to be Sony or Toshiba, but I have never really paid much attention to them. Are there any that aren't constrained by interlacing, 576 lines or 15.625 kHz refresh rate? Anything that could take 720p or 1080i, perhaps?

    Anybody know much about them?

    Nick
     
  2. Chris Frost

    Chris Frost
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    Rear Pro CRT is enjoying a bit of a renaissance at the moment. Mostly this is down to price. It’s a bigger picture for less money than LCD / Plasma. There are a few 100Hz models around, but very little (if any) that will accept a HDTV signal.

    LCD and DLP have been used in rear-pro sets for a few years now. Prices are higher, but with a digital light engine you are more likely to find some thing that will accept HDTV signals. Thomson makes a HDTV compatible 50” – sells for approx £3k. Sim2 has a couple of models towards the top end of the performance spectrum.

    The reason why the contrast looks good in daylight is because the screen is dark grey or black. The better models use a ribbed screen that looks like a pin stripe effect from the front. The pin stripes help absorb ambient light, this makes the viewing side of the screen look dark even in high ambient light. The back of the screen has light focusing micro lenses. They scavenge much more of the projector light than a simple transmissive screen. The result is much greater light efficiency and better contrast. There’s more info about this screen technology at www.rearpro.com Have a look at the Black Bead screen to get an idea of what is possible.

    Regards
     
  3. Welwynnick

    Welwynnick
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    Thanks Chris,

    I had been wondering if it was possible to get away from ambient light pollution, and get a high contrast image while the wife can still see to do the ironing. Or when I do the ironing, of course!

    If the screen is actually black rather than white in ambient light, that's got to help the contrast in the daytime. But is the screen actually black? Does it attenuate transmitted light? It sounds like there might be a play-off between brightness and contrast here, as there is with grey front pro screens.

    Cheers, Nick
     
  4. Chris Frost

    Chris Frost
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    Ah, I see your point of confusion.

    First, not all rear-pro screens are the same. Cheap ones are little more than frosted perspex. The next level up use a fresnel lens to redirect the light, this is better but the screen still looks light grey and suffers poor viewing angles.

    The best screens are made by DNP. They're constructed in several layers. At the back is a light focusing fresnel lens. Next you have another set of lenses to redirect the light to give a wider viewing angle. The front element is the ambient light absorbing strips. Viewed up close from the front you would see a fine pin stripe effect. Black bars interleaved with the vertical columns of micro lenses. Each stripe about the width of a ball-point pen nib. Viewed from more than a few feet away the screen looks black.

    The final viewed effect can be better than conventional CRT TV.

    I'll write a bit more later.

    Regards
     

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  5. Welwynnick

    Welwynnick
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    Any idea which manufacturers and models used the DNP screens?

    Nick
     
  6. Chris Frost

    Chris Frost
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    Nick, your best bet is to check with the TV manufacturers.

    [ OT : I wrote the same reply to this thread over the weekend but that post seems to have disappeared. How odd :confused: ]
     

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