Originally Posted by *UFO*
I do not want to get negative gain though, otherwise I would go with the high power. With my setup using the calculator im at about .7 gain.
Are you sure?
With the projector mounted only 1" above the screen, you will not be anywhere near negative gain territory on a Da-Lite HP 2.4 gain screen. Also, FL Boy's calculator is brilliant, but I am not sure of its' angle accuracy when it computes the distance you are sitting from the screen, because when I've tried this before it seems incorrect.
For instance, if I recall correctly (and perhaps I don't), but I remember it claims when I am in the same center-sitting position at 9 feet from the screen, I am getting 1.2 gain in my setup, but at 15 feet it says my eyes are receiving 1.6 gain (now I am not 100% either way, but it surely does not appear this is correct).
I suppose the perceived gain changes somewhat because as you sit farther back, the entire perimeter of the screen is within your viewing field, meaning the edges or outside the center of the screen now appear brighter as you sit farther back because there is less angle between the perimeter around the center and your eyes. However, the problem with this gain calculation theory, is that the immediate center of the screen's gain should not change much just by moving back (though towards the edges the gain changes more due to angle decreasing faster as you sit back), but I don't think that much as it states to how the eyes perceive the gain.
The reason I see the hole in this is because it's hard to say exactly how the eyes perceive this moving farther away, since when you are closer to a screen your eyes are actually receiving MORE light in the total viewing area of your pupil's peripheral vision than as opposed to sitting farther back.
However, it does make some difference on how far up you are sitting from the projector when using the Da-Lite screen (because this affects viewing angle of edge of screen even if you are in middle but sitting very close), so you do have to take that into account, but I just think his calculator might be exaggerating the difference as the eyes perceive it, but I am not sure either way as I haven't tried to break down the numbers myself. Anyhow, I didn't mean to open up a can of WORM theory, but just some food for thought (if you like eating worms that is)...