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Increased brightness from line doubling?

Discussion in 'Projectors, Screens & Video Processors' started by drago.d, Jul 3, 2003.

  1. drago.d

    drago.d
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    I have read somewhere that line doubling/scaling a crt pj increases its light output. (But then, this could just be wishful thinking on my part, of course.:D)

    If it does, however, it raises two questions: 1) by how much does the light output increase, and 2) should this increase in output be factored into the decision of which screen gain to use?

    My Seleco 500 is rated at 140 ANSI, which I understand ain't that much, so I could probably use the additional output.:smashin:

    BTW:
    The pj will be ceiling mounted, and I have calculated that with 140 ANSI, on an 80" wide, 16:9 screen of 1.3 gain I'd get about 7.3 ftL, and with 1.5 gain 8.4 ftL.
    I know I could consider a smaller screen to raise the ftL, but the view distance looks like being 14+ ft.

    If anyone knows what the heck I'm talking about, could they please enlighten me?

    Cheers,

    drago.d
     
  2. Chris Frost

    Chris Frost
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    drago.d, your 500 is already line doubled unless you have turned the feature off.

    Don't worry about the 140 ANSI lumens figure looking low compared to LCD & DLP projectors. The ANSI measurement favours fixed panel projectors doing computer presentations. This is why CRTs are normally measured in Lumens.

    Your 500 will be capable of generating spots of light equivalent to a 1000 ANSI lumen LCD projector.

    80" wide is about 6 1/2 feet. A well set up 500 will look great on that screen size using a 1.3 gain screen. I have used them on larger screens. A 9ft 16:9 Stewart StudioTek 130 (1.3 gain) looked better than I had expected, though I think that's definately pushing a 500 a little beyond its limits. 7ft is a better size.

    Ask whoever is doing your convergence to check the level setting on the Peak Limiter. This caps the maximum light output. The Seleco factory set these on the very conservative side during manufacture. A good installer will know how to get in to the service menu and where they can safely set the level.

    Good luck.
     
  3. Roland @ B4

    Roland @ B4
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    There's two sides to this coin.
    A line doubler will increase then number of lines and hence the amount of phosphor that is used this should make the image brighter.
    However there will be extra draw on the powersupply and this can on the lower end machines cause the image to get dimmer as it struggles to cope. As Chris says the 500 has a line doubler built in and has been designed to cope.

    If you think the game the LCD/DLPs are playing with ANSI brightness figures. Wait till you start comparing contrast ratios. If we use the same calculation that these chaps use for the 1000:1 they claim to achieve then your average CRT will be around 30,000:1
     
  4. drago.d

    drago.d
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    Chris and Roland, thank you for your replies.

    I take it that the possible increase in brightness isn't worth factoring into the choice of screen then? (I suppose it may allow the brightness setting on the 500 to be reduced slightly.)

    Chris, you mention a screen gain of 1.3. Would this be the optimum choice, or is it worth considering a 1.5/2.0 gain (pj ceiling mounted)?

    As far as installation, convergence, Peak Limiter, etc., Chris, you have mail.

    Cheers,

    drago.d
     
  5. Chris Frost

    Chris Frost
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    You can get a Matte White screen with a gain of 1.3 which will give great viewing angles without introducing hot spots or giving problems with Red/Blue colour shift across the screen surface.

    I don't know if there are any 1.5 gain or above screens that will do the same. Roland and Gordon have more contact with screen manufacturers so are probably better able to help you with this question.


    Regards
     

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