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Somewhere I have heard that the biggets screen size for 9" CRTs is 90" diagonal. Is this correct?
 

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cai,

This depends on several factors but I've seen approximately 90" wide ( not diagonal ) at 16x9 as the number. You must also consider screen gain, and type of 9" CRT. G90s are unfiltered and have the highest light output and therefore can support the largest screen of the available 9" units. Some would argue this is at the expense of color accuracy.

Art
 

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Well, let's see here:


My NEC XG110LC puts out 1200 lumens. Using a 1.6 gain screen, which may be a bit much - I don't know, and targeting 20 ft. lamberts, I could have:


FtLambers=lumens * screen gain / sq. ft. of screen

20=1200(1.6)/96

96 sq. ft. of 16:9 ratio is 13'1"x7'4"', or 157"x88" (approx)

Diagonal would be 180"


This is using 8" guns.


If I use a matte white screen with no gain, I can still get 60 sq. ft., which is 10'3"x5'10", or about 141" diagonally.
 

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I use a stewart 1.3 gain perforated screen at 95" width for my 9" CRT (9500 lc).

Room colors should be also very dark and non reflective. Black is preferable of course but it may not be practical in many situations.


Generally speakign 85" width is said to be the most ideal - I am not an expert at this but I am told it would give the 12 to 14 ft lamberts which is suggested as being ideal.


Some have screens in the 100" to 120" width range and they seem to be quite happy. An expert commented to me that he may not object to a 100" - 105" width screen. He truly is the expert and I am not. Even then, I would still say that 100" width is too large for my personal preference. YOu may end up driving the tubes hard too if you go too large.


If your situation allows 85" to 95" width, it should be a pretty safe bet - 85" being more preferable to 95" of course.
 

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Quote:
Originally posted by nrubenstein
You need to use ANSI lumens for that number. Peak-white lumens are more to impress than anything else.
I do not believe that ANSI lumens would work in that equation. My projector puts out 240 ANSI lumens. Using the above equation, I would only get 12 sq. ft of screen area at 20 ft. lamberts. That is a 3'x4' screen, or a 60" diagonal. I am fairly certain that the image would be amazingly bright on a 5' diagonal screen with 8" guns on full output.


This equation works with peak-white output. Sure, you could modify the equation to work with ANSI lumens, but many digital projectors don't report ANSI Lumens, which would make it impossible to calculate.


I used this equation for my digital PJ, an NEC LT150, which running 48 sq. feet full panel at 2.6 gain yielded 370 lumens required to acchieve 20 ft. lamberts. The projector is 700 lumens, but I turned off the white segment and painted the color wheel, plus ran a filter. My best guestimate is that I should be around 350-400 lumens now. The picture is quite acceptable to all but die hard CRT fans. Even still, it is not a brightness issue that would be objectionable.


14-20 Ft. is desireable for proper viewing conditions


Ft Lamberts=Peak White Lumens X Screen Gain / Total Square Footage of Screen


If this is off base, I would like to know, but it has worked so far and would like to know before I get myself in a pickle with a screen that will give me a suntan or a picture that looks like I accidentall forgot to remove my welding hood.


Besides, don't ANSI lumens include some areas of the screen as black? Wouldn't that mean that having blacks as black as possible reduce your lumen output, even if the peak white output is the same? And trust me, I don't want 14-20 ft. lamberts of screen luminescence when the screen is all black.


Mike
 
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