Originally Posted by shawxnmr45
From the w1070 blog review: " The W1070 does have a small amount of physical vertical lens shift, but you need a screw driver to make adjustments. For the horizontal adjustments, BenQ implements software keystone correction. The combination isn’t the worst I’ve seen, and it’s kinda surprising to see physical shift at all on a DLP projector, but it certainly isn’t the best. I was unable to fill my screen with the w1070 in the location that I currently shelf mount my 6500UB, so placement location should not be an after thought if you are thinking about this projector.
That quote is incorrect, there is no horizontal adjustment of any kind. You have to put the projector center of the screen (or move your screen). For those who need installation flexibility lens shift is the best option. Projectors like the Epson 3020 actually have digital keystone correction for both horizontal and vertical. Not ideal, but Epson does consider it their entry level projector, despite the price tag.
Originally Posted by DavidK442
2) Lens shift is a physical adjustment of the lens, keystone correction is digital adjustment that can reduce the sharpness of the picture.
May as well explain this as it's important to understand. Lens shift works like a tilt-shift lens in photography (see: http://www.youtube.com/watch?v=0HRYlJUwzYA
). Basically you level the projector and square it to the screen and just move the lens around to place your perfect rectangle image anywhere you want (within limits).
Now, imagine you don't have lens shift and the projector isn't perfectly square on the screen. When you angle the projector to hit the screen, the image will form more of a trapezoid (in each direction you angle it). Think about a flashlight when you're pointing it at a wall directly ahead of you it makes a circle now as you tilt it up/down/left/right the image it produces starts to elongate and produces an oval. Either way, in order to "fix" the trapezoid shape, software correction rescales the image internally. Obviously doing this, you lose perfect pixel mapping, however this is usually pretty hard to see unless there's an extreme amount of keystone correction, you sit close to the screen to see the pixel structure or if you're viewing content which requires perfect pixel mapping (i.e. computer content). It loses sharpness, think of it like displaying a resolution on a monitor which isn't native.