Originally Posted by socwrkr
Thank you for the reply. I am familiar with what lens shift is. Maybe my thinking is way off (hopefully it is) but what i'm trying to point out is that the projector will be mounted on part of the ceiling that is lower than the part the image will be projected on. Wouldn't the ceiling that it is mounted on get in the way of the projected image if i shift the image up (see photo)?
Oh, you are talking about line of sight!
I think the laser pointer, as mentioned above is a great idea. The flashlight may work as well.
As string pulled from the top of the screen (image) location to about 6" below the top of the 80" section also will give you a sight line clearance.
What you are talking about, I've heard before, but the upward angle to the top of your screen should be very little and it only needs to clear the front edge of the ceiling, which will be a couple/few feet in front of the lens.
If the top of the screen is at 90" from the floor and the lens is at 74" and you have 144" from lens to screen, but only 24" from the lens to the edge of the lower section, then the image will rise 16" over the full distance from lens to screen.
2/12 (2 feet/12 feet) = 1/6. 16"*1/6= 2.7" of rise by the edge of the ceiling. So, you will have a bit over 3" to spare.
If you had it at 14 feet lens to screen, same measurements... 4/14 = 2/7. 16"*2/7 = 4.57" - so about 1.4" of clearance.
I'm assuming certain numbers and locations here, but hopefully you get the idea on the math itself and how to work things out... and that you really shouldn't have any issues with clearing the ceiling as the image travels upwards a bit.