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Discussion Starter · #1 ·
Can someone explain the relationship between maximum resolution and a given aspect ratio. It seems to me that if you set up you memories in the projector for a constant height picture varying the width as you go from 4:3 to 1;77 to 1:85 to finally 2;35 you limit the vertical space available for effective quadrupling. In other words, doesn't forcing all the scan lines on a 9 inch crt so close together in a 2:35 aspect ratio begin to blur or bleed the light output of each line over to the other in all the other aspect ratios? Remember I'm talking about setting up the aspect ratios so all the screen heights are the same. This necessitates vertical letterbox bars not horizontal.

It's very theater like to have ever wider screens as you get to 2:35. The alternative is to set up the projector so the width is constant, varying only the height giving the traditional top and bottom bars. And doesn't this method maximize the space available for the scan lines as you go from 2:35 up to 1:85?

I'm in that "which screen do i get" dilemma. I have a 9 inch crt with a faroudja #3000. Do I get the 1:85 or should I get a 2:35 screen? And if the screen gets wider, light output drops due to the throw distance. Should I then get a 1.5 gain or a 1.3. I'll probably get a Stewart.
 

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In a constant-height configuration, a 2.35:1 aspect ratio screen will allow use of only about 1/3 of the CRT vertically. A 4:3 aspect ratio then becomes a "postage stamp" in the center of the raster, increasing the risk of raster burn. Both limit light output, as you noted.


Before scaling processors became available, the number of different aspect ratios possible was often limited by the horizontal width range of the projector. With most, a range of 4:3 to 1.85:1 was about the limit. Since your Faroudja does it's aspect ratio control based on this, I would stick with a 1.85:1 screen. It is also my opinion that screen gain beyond 1.3 (StudioTek 130) is not an acceptable compromise with components of this calibre.


Ken Whitcomb


Now Photo Research PR-650 equipped!
 

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Discussion Starter · #3 ·
Ken:

Stewart screen says that if I choose a 100 X 54 1:85 screen, a 1:5 gain screen would be necessary to achieve 8 ft. Lambert's of brightness. Do you think color shift or hot-spotting would be noticeable over the 1:3?

I, too, am leaning toward the 1.85 screen. My previous set up was a runco 900A on a 96inch wide 1.85 screen using a their doubler. That screen was a 1.3 gain Da-lite fixed frame. It seemed bright but I know light falls off quickly with every inch. Stewart's catalog lists a 16X9 at 96 inches wide but not a 1.85. The 1.85 is 100 inches wide. Of course Stewart will make anything you want but custom sizes get expensive. I've heard the 1.5 gain screen is color corrected for CRT applications. Do you have a front projector?

Got two cents?

Rich
 

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Dr.Rich,


Stewart bases their recommendations on actual measurements taken in the field by specialists such as myself. However, as a screen company, they recommend what is required to obtain the overall suggested output. I work with dealers who install many 9" CRT projectors, and StudioTek 130 has always delivered superior colorimetry and uniformity. I would always recommend a smaller screen size first, before any additional gain.


If you found the image satisfying on your previous screen, stick with a 1.3 gain. I maintain a Runco DTV-1101 stacked pair on a 60" x 111" screen and, even with their additional lens filtering, the StudioTek 130 is still enough.


Ken Whitcomb


Now Photo Research PR-650 equipped!
 

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Discussion Starter · #5 ·
Ken:

So, do you think a single projector and processor would work well with the 100 inch Stewart 1.3 gain. Have you set up systems like this and found the results to be acceptable?

Rich.
 

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Rich,


If you have total light control in your theater, I think you would probably find a 100" wide StudioTek would be acceptable. One of the dealers that I work with displays the Runco DTV-1101 (one of the lowest output 9" projectors) on a 54 x 96" StudioTek. Another specs that screen as standard in most of their Sony G90 installations.


The human eye will generally accept lower overall light output if the contrast ratio is high enough. Just keep light from infiltrating the room, and reflected light to a minimimum (dark walls, carpet, and ceiling).


BTW: To answer your previous question, I use a Runco IDP-980 Ultra with a Runco VHD-4404 Ultra processor (scaling to 768p).


Ken Whitcomb


Now Photo Research PR-650 equipped!
 
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