Originally Posted by vidkidd
Some additional information to keep you confused.
From what I've seen, the only way The 1080ST/W1070 can achieve a clean 1:1 focus over the entire projection area is to mount the projector at with it's Optical Zoom lens
set to a maximum size at the distance that works for the size of your screen. Do not count on using any digital zoom or keystone as they destroy the pixel map and any hope of true clarity. Anything less will keep the projector from throwing a "clean" image. IMO, color and luminance calibration are secondary to attaining a proper focus.
Interesting. I've been using the projector on a coffee table and was going to ceiling mount it tonight. On the coffee table, I've been using it in the closest position to the screen (10') for my preferred image size (120" diagonal), I was planning on ceiling mounting it close to the farthest position from the screen (13'), minus a little wiggle room, e.g. about 12'6" from the screen. That location follows the conventional wisdom that a longer throw maximizes contrast, at a modest reduction in brightness, and should maximize image quality, including focus, because it's only using the best, central parts of the lens. Plus it gets the projector as far back as possible and out of my peripheral vision.
I hadn't really thought about it, but at the close position I was able to get the focus close to tack sharp across the full picture, whereas farther back it does seem like I'm having to trade off focus a little across different parts of the screen. I think I'd assumed the projector wasn't perfectly parallel to the screen, and this would be fixable via fine-tuning the mount. It seems counterintuitive that using the full lens would yield better focus than just using the best, central parts of the lens. But now I'm going to have to play around to make sure I can get good focus with a long throw. Thanks for bringing this to my attention! Will be curious if others are having similar experiences.
EDIT: Thinking about this further, I wonder if what's going on is that you and I were both using slightly off-horizontal surfaces from which to project. When the projector is closer to the screen, this has less of an effect, but pulling it back away from the screen maximizes the effect of the same angle. This suggests that fine-tuning the angle on a ceiling mount, or for that matter of the projector feet when it's sitting on the coffee table, should fix the observed inability to maintain focus across the screen. I can't come up with another plausible explanation for why we'd observe this phenomenon otherwise, it seems like the reverse of what one would expect.Edited by niccolo - 11/8/13 at 3:01pm