What type of screens?

[BPoese]

We are making a large room in our church basement into a small "conference" center. The dimensions of the room are 38 feet by 42 feet. The ceiling height is only 8 1/2 feet. The "stage" is only 6 inches high and is about 7 feet deep by 21 feet wide. We are thinking about installing 2 "screens", one on each side of the stage. The question is what type of screen are we talking about. We don't want something that people will be walking through the image during the conference. We want something big enough for the people in the back (about 35 feet way) to be able to see and read. I am assuming PowerPoint (PPT) slides are what will be used most of the time - realizing that we are at the mercy of the PPT creator. But I at least want to give them a descent chance at creating a PPT slide that can be seen 35 feet away. The two proposals so for have been to use two large LCD screen or two Brightlink board (although the ceiling may be still too low). What size of an LCD screen would we need? Are there any other recommendations? The back wall of the stage is the exterior wall so we can not use rear projection. Someone suggested a short throw projector in the stage floor but I'm not too in favor of that because the stage is only 6 inches deep and the presenter now has to stay out of the image himself, or am I missing something with that suggestion?
Thanks
Bruce

[[Admin] osborn4]

It really depends on what you are going to do with the screens.

The general rule of thumb is that the screen height should be 1/8 of the distance of the furthest viewer. If that's 38' then the screen should be 4.75' high.

Then you figure your width after you decide if you're going 4:3 or 16:9 and from there you should be able to figure out your diagonal.

If you go 16:9 (I can't imagine not going wide screen on a new installation) your width is about 8.5' which gives you about a 9.75' (117") diagonal.

If you're just going to do words, you can go smaller. But this is the recommendation I've heard if you're going to show videos or graphics.

[Brad Weber]

The rule of thumb I know is 1/8 the distance to the furthest viewer for general viewing, 1/6 for typical computer graphics and 1/4 for 'critical viewing'. Text can be an 'it depends' situation as it is very dependent upon the character size, a PowerPoint slide with large font text is a very different situation than someone trying to review financial figures in a spreadsheet or read the 'fine print' of a contract.

So with viewers 35' away in a conference room application I might look at a 6' high image (actually, I did exactly that just yesterday!). However, the 8'-6" ceiling height may make that impractical. You don't usually want the image right at the ceiling as you can then get glare and reflection off the ceiling, so the top of the image might be at 8'. And with a flat floor you typically want a minimum of 3', and preferably 4', from the floor to the bottom of the image to minimize interference at the bottom of the image resulting from people sitting in front of one another. That means that with the 8'-6" ceiling height a 4' to 5' image height is probably all that is really practical, which may limit viewing a bit for some applications.

With a desired 48" to 60" image height and LCD/plasma displays being 16:9 format that would be a 48"x85.3" (98" diagonal) to 60"x106.67" (122.4" diagonal) flat panel, quite a bit larger than any reasonably priced single direct view display. The BrightLink 455Wi is 16:10 format so that's 48"x76.8" (90.6" diagonal) to 60"x96" (113.2" diagonal). The 455Wi can support up to a 51" high image, however with an 8'-6" ceiling and maintaining a minimum 36" from the floor to the bottom of the image pretty you are apparently limited to a 40"x53" (67" diagonal) image, which equates to good viewing for a person 20' (6:1) to 26'-8" (8:1) from the screen.

Depending on budget, standard front projection using a projector that can be below the top of the image or tiled LCD/plasma displays would seem to be options. So might be using ceiling or wall mount 'fill' displays for the viewers further away.