Projector tilt question

[maniacalpha1-1]

I'm thinking of getting a projector and I plan to just stick it on a bookcase or something point across the room. Now, I notice from using projector calculators that, for example, on a flat surface (table mount according to the calculators), if I were to say, put it on something 4 feet high, then the image is going to be 4 feet 8 inches from floor to bottom of image...is it OK to just put a shim or something on the back of the projector to tilt it a few degrees? (obviously if the lens has some kind of built in tilt then this is a non issue).

The one I am thinking of getting is a BenQ EP5920, it's the cheapest 1080p projector out there. Otherwise I was just going to get an even cheaper 1280X800 projector(that's more than enough to meet the native resolution of DVDs I believe).

Just for reference I looked up its manual and it first says "Always place the projector on a level,horizontal surface during operation." But then it goes on to say "Do not use if tilted at an angle of more than 10 degrees left to right, nor at angle of more than 15 degrees front to back." So I'm guessing I'll be OK tilting it 3-4 degrees forward?

 

[ArJuN]

If you tilt the projector, you're going to introduce a distorted image that will be in the shape of a trapazoid. That's because the distance from each side of the projected image won't be equal. (In your example, the top of the screen will be thinner than the bottom.)

To combat this, a lot of projectors have a keystone function that essentially manipulates the video feed to counter the distortion to make it look like a rectangle. But using the keystone setting affects your picture quality because it's essentially squeezing and stretching the image. In your case, I'd suggest getting a projector with a significant amount of lens shift. Lens shifting physically moves the lens giving you the ability to move the image vertically and horizontally without affecting the quality or shape.

I'm not familiar with BenQ's line, but it is odd that the projector projects an image higher than its position (that's usually saved for office projectors). Reviews do state it has a keystone feature so you could get away with it if you're willing to take a hit on the 1080p. Otherwise lens shift is what you're looking for in a projector.

A cheaper way to combat the problem is to just tilt your screen to the same angle as you did on the projector making the lens and screen parallel to each other.

 

[maniacalpha1-1]

Hmmmm...well I notice that the calculator shows ceiling mounts as projecting downward relative to their placement. Having never had a projector before this may be a dumb question but does that mean the mounts are on the bottom of the projector? (ie, mounted upside down)

 

[sdifox]

Hmmmm...well I notice that the calculator shows ceiling mounts as projecting downward relative to their placement. Having never had a projector before this may be a dumb question but does that mean the mounts are on the bottom of the projector? (ie, mounted upside down)

yes, most mounts are on the bottom of the projector.

 

[maniacalpha1-1]

Well, I think my best bet is "ceiling" mount orientation but I don't want to mess up the ceiling. Are there any 8 foot stands that will allow the projector to be held upside down?

 

[purbeast0]

not sure if this is common or not, as i've only owned one projector, but mine has a control on it like a joystick that you can move around to shift the image up/down/left/right and it doesn't distort it at all.

 

[maniacalpha1-1]

Ah, I figured out that the EP5920 does seem to have lens shift, at 12 feet throw distance which is what I have available it should be able to make a 91 inch image and shift it down 7 inches if I need it; this should allow me to do tabletop...nice!

 

[vshah]

as long as you buy a projector with zoom and horizontal & vertical lens shift, you'll be fine.

 

[Spicedaddy]

Ah, I figured out that the EP5920 does seem to have lens shift, at 12 feet throw distance which is what I have available it should be able to make a 91 inch image and shift it down 7 inches if I need it; this should allow me to do tabletop...nice!

That model doesn't have lens shift. It'll do digital keystone, and it'll hurt image quality.

My suggestion would be to put a shelf high on your wall and screw the projector under it...

example:
http://www.isk.kth.se/~amalmg/pics/mitsu.jpg

 

[maniacalpha1-1]

So I got an Optoma GT750e short throw projector and I'm liking it.

Can anyone confirm that this is the right material to buy if I want to make a rear projection screen?

http://www.amazon.com/Diagonal-Rear-...creen+material

 

[purbeast0]

thought you wanted to point it across the room from a bookshelf? that isn't rear projecting, that is front projecting.

rear projecting is if you had the projector behind the screen pointing at the screen.

 

[maniacalpha1-1]

thought you wanted to point it across the room from a bookshelf? that isn't rear projecting, that is front projecting.

rear projecting is if you had the projector behind the screen pointing at the screen.

Well, I got a short throw so it can't be across the room anyway. That screen material looks pretty affordable so I was thinking it wasn't the right kind...