I’ve been using two projectors for a while now, neither are short-throw. Now I want to do a new installation using 2 short-throw projectors. This new project spurred me to really research projector technology for the first time. What I learned is that most projectors in general, especially sub-$2000 short-throw projectors are designed so that the projector will be placed above or below the actual screen. This is called the vertical offset of the projector and each projector has a vertical offset ratio that can be used to determine the offset at a given distance. Adhering to the offset ratio should, in theory, give you the clearest possible projection.
If you checkout Optoma’s distance calculator you’ll see that every Optoma projector is designed to be placed above or below the actual screen.
http://www.optomausa.com/distancecalculator.asp
Interestingly though, I called BenQ and ViewSonic and representatives from both companies could not tell me what were the offset ratios for their projectors.
The really high-end of InFocus projectors allow you to manually adjust the “vertical lens shift” of the projector (which changes the angle of the lens I believe), essentially allowing you to adjust the offset ratio.
Over the phone, an InFocus tech warned that taking a projector without lens shift and angling it with a ceiling mount to essentially lower the offset ratio and using keystone adjustment to make the image square would negatively effect the life of the projector (he didn’t say those dreaded words, “nullify your warranty” but I did get the feeling it was on the tip of his tongue).
The ViewSonic tech I spoke to said I could angle the projector any which way I pleased, no prob, bob.
Anyway, after all this research I realized that I had improperly mounted my Optoma HD20 projector a year ago. Currently the projector sits a good two feet lower than the top edge of the apx 13 ft wide screen. Optoma recommends a 14" offset meaning my projector is mounted a good 3’ from where it should be, ideally. Thing is, I’ve never noticed. The picture looks great. (I believe that in theory an improperly mounted projector should have one edge that is more out-of-focus than the other)
So after all that, my question is… can I cheat with short-throw projectors? Can I mount a projector intended to be 9"-12" inches above the screen 1 or 2 feet below the top edge of the screen? I suspect that long-throw projectors might have more leeway than short-throw in these sort of circumstances. However, can anyone shed any light on this issue who might have experience with short-throw projectors?
This is the projector I’m thinking about doing this with…
http://www.viewsonic.com/products/pjd7583wi.htm
( Or… do you know of a sub-$1600 720p short-throw projector that would fit the bill? )