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So, everything was GREAT about our home theater set-up...

D

dc0ccc

Junior Member
Until we turned it on.
So we've had a week long project of transforming our college dorm into a home theater for under $1200. The proj is the optoma HD and we get a nice 1080p on 119 inches.
Unfortunately, it's crooked
Since we don't want to keep putting holes in our ceiling, do you guys have any tips on how to angle it/measure it so we KNOW it's straight (aside from eyeballing). Here are a few pictures.

http://min.us/mvbDojc#icsZMChttp://min.us/mvbDojc#icsZMC

We've dealt with it for a while, but frankly, it's really getting on my nerves now
 
dc0ccc said:
optoma HD66 : http://www.newegg.com/Product/Produc...82E16824219084

we're actually all inexperienced in any kind of handy-work at all, but the ceiling mount would kind of force the projector to be level on a horizontal plane, right?
Is there a way we could use the leveler to determine which angle would hit the screen flat on and not sideways?
Click to expand...


use a level to first make sure your projector is level

then measure from the edge of the screen to the edge of the lens. They should be equidistant.

Then you can use adjustments on HD66 to fix your geometry.

Ideally you can get a rectangular image without resorting to adjustment of geometry in the projector.
 
The projector lens is not centered on the screen. It's closer to the right edge, which is why the left side is angled downwards. It's not because the projector isn't level. The image offset gets larger the further the screen is from the lens. Since the left edge is farther away from the projector, the offset is larger, the end image bows downward.
 
i just mounted a shelf on the ceiling. the projector is then easy to take down if needed, and to get the tilt right all you do is stick some cardboard under one side...
 
dorm rooms sure have gotten fancy. We thought we were awesome in our quad with our 26 in tube tv and surround system.

you should be able to use a level to level it and then mark your center line on your wall and center the lens with that mark.
 
It looks to me two things are going on.

1. The projector is slanted down to the left.
2. The projector is not at a right angle to the screen:
___
..\..
instead of
___
..|..

I think 2 is what Knightbreed is saying, I agree. Even if the tilt was fixed the left side of the screen will still be taller than the right because of the angle to the screen.
 
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Modelworks said:
That is why you use a gimbal mount. It adjust on all 3 axis.
Click to expand...

If the projector had lens shift, then your solution would solve any issues.

Since it looks like the projector does not have this feature, it is essential that the projector is lined up with the center of the screen (horizontally) and shooting light perpendicular to the screen.

You can twist and turn the projector all you want with a gimbal mount, but if the projector is not in the right place to begin with, you will not be able to get it to line up with the screen correctly.

If the projector isn't mounted in the middle of the screen horizontally, one side of the image will be larger than the other (since the light has a farther distance to travel to one edge of the screen). If the projector has to be mounted in that off-center position, you either need lens shift or horizontal keystone correction to fix the issue.
 
YOyoYOhowsDAjello said:
If the projector isn't mounted in the middle of the screen horizontally, one side of the image will be larger than the other (since the light has a farther distance to travel to one edge of the screen). If the projector has to be mounted in that off-center position, you either need lens shift or horizontal keystone correction to fix the issue.
Click to expand...

Unless the projector is horribly off center, more than a 1/3rd of the screen width, or is at an extreme distance ,there wouldn't be any skewing of the picture. Keeping the projector parallel with the screen is more important than centering the lens. If the projected image is planar to the screen then no keystone correction is needed regardless of where the center is located. Off center you would not have a distorted image, just one that runs off screen.
 
Modelworks said:
Unless the projector is horribly off center, more than a 1/3rd of the screen width, or is at an extreme distance ,there wouldn't be any skewing of the picture. Keeping the projector parallel with the screen is more important than centering the lens. If the projected image is planar to the screen then no keystone correction is needed regardless of where the center is located. Off center you would not have a distorted image, just one that runs off screen.
Click to expand...

Well, I think my point is that if you

- Want the projected image to line up exactly with the screen
- Don't have lens shift of the projector
- Want the projector parallel with the screen

that leads you to needing the projector at the midpoint of the screen horizontally (unless the projector is designed with some horizontal offset or something).

Of course he could just make the projector parallel to the screen now, but that's not a solution to his problem because there's no way he can move the screen to match where the image would then be.
 
I have a projector, no lens shift. It has to be centered to the screen for a properly square image.

Maybe I can do this with pics:

_____
....|.... = square, centered image

_____
.....\... = skewed, centered image

_____
.....|... = square, off-center image

So unless you have the mount point with the lens at the center of the screen you're going to have a problem.
 
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