Projecotr HX2, screen VUTEC Silverstar retractable 120" wide 2.35:1 screen, panamorph lens. To be hung in the middle of teh room from the ceiling. My question is really how do I ensure that my PJ's line to the screen is perpendicular to the plane of the screen.
I've read that the easiest way is to take a piece of string and measure from the middle of your lens, to each of the 4 corners of the screen. it should be the same length when you have the items positioned correctly.
First I established a level line at the bottom of where the screen was going to hang with a self leveling laser level. Next instead of a string I used a plastic covered plant twist tie. It has a metal core, doesn't stretch and is very light (no sag) (Home Depot). You can get 50ft for $3. I started from the outside bottom corners where I planned on placing my screen and scribed two sets of intersecting arcs on the ceiling. I connected the two intersections with a line to determine the center line for the projector mount. I checked the distance to the screen from this line and hung the mount. Actually I had to measure an offset from the center for the lens position.
Then I hung my projector.
On my projector there is a knob that the len's cover attaches to, centered above the lens. I looped the wire over the knob and then double checked back to the front to be sure that the screen was positioned properly. It was.
As for height I just measured from the ceiling to be sure that I was lower than the upper edge of the screen.
Your projector mount needs what is called by engineers three degrees of freedom. In other words it should be adjustable in the pitch, roll and yaw directions. This will allow you to center your picture in the screen. I'm assuming you can mount the PJ in the middle of the screen left to right without much difficulty.
My experience is that if you're a little out of square you can't tell the difference.
The Keystone adjustment on the PJ is more important.
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