CurtPalme.com Home Theater Forum

armstrr · Joined: 26 Mar 2006 Posts: 160

everything i am able to find starts with raster set up, but never mentions a good method to actually ensure the pj is mounted perfectly center relative to the screen and parallel.

so how did you guys do it? i can see it being a lot easier measuring with 2 people. if this has been covered before, please point me in the direction!

thanks!

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

For centering I generally use a large rectangular piece of something, or a large square, to sight from the center of the screen. It's not perfect but it gets me pretty close.

For getting square to the screen, I use a much more sensitive method: http://www.curtpalme.com/forum/viewtopic.php?p=79360#79360

armstrr · Joined: 26 Mar 2006 Posts: 160

thanks g-fritz.

you and i are on the same page. i cut a piece of 3/4" mdf about 4" wide by 8'. there are lots of square aluminum extrusions on the marquee. i'll get someone to hold the mdf against the aluminum front edge and do some measuring. thanks

sometimes low tech is good!

ecrabb · Posted: Fri Oct 17, 2008 6:42 pm Post subject:

I don't know - a very small error in square on a 4" edge will accumulate to a large error over 8 feet.

I use a tape measure to find screen center (very accurate), the good old "3-4-5" right-angle method to find the orthogonal from screen center (very accurate), and a spinning laser level to extend the line and put it all together. You can get the projector and projector centerline to within 1/16" of an inch using this method.

I detail my method in this thread:
https://www.curtpalme.com/forum_archived/viewtopic.php@t=12056.html

SC

perisoft · Joined: 29 Aug 2007 Posts: 2920 Location: Ithaca, NY

I hit the unistrut with a hammer.

Axatax · Posted: Fri Oct 17, 2008 8:59 pm Post subject:

1. Turn PJ upside down and install mounting plate. Snap a chalk line from the center of the mount, over and around the top of the PJ case.

2. Place PJ on cart, maximize and center rasters.

3. Drop a plumbob from the ceiling to the center of the calk like on the PJ. Mark the ceiling where the plumbline originates. This is where the center of the ceiling hardware will go.

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

SC is right -- 4" is too narrow. When I use a rectangular piece of "something," I use something at least 2-3' wide. His 3-4-5 is a good method, and the laser level is a good toy but I don't have one. Smile

stefuel · Posted: Sat Oct 18, 2008 11:54 am Post subject:

There is a very easy way to do this if you have any type of laser device. Locate the center of the screen on the wall. Tape a large mirror at the top of the wall over that point. Transfer that point to the top of the wall and mark on the mirror with a felt pen. Go back to the proposed projector mounting area and point the laser at the mark on the mirror. Move the laser side to side and find the point where the laser bounces back and hits it's self. That's close enough for even the most demanding crt installation and one person can do it alone.

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

Very clever!

You'd want to use a reasonably large mirror -- a little 3" or 4" mirror might not sit flat on the wall, throwing off your reflection -- and attaching a large mirror to the wall (assuming no helper to hold it) might be a challenge. But it's a slick solution!

jkruger · Joined: 24 Oct 2007 Posts: 2435 Location: Carlsbad, CA

After centering the pj to the screen I take measurements from the corners of the screen to the corners of the pj both front and rear in a trapezoid and diagonally similar to the crossed stings method. My unistrut mount is also a trapezoid to keep swinging movement to a minimum. I've found that when the party starts swingin' so does the pj.

J Kildare · Joined: 28 Sep 2006 Posts: 164

My personal way of doing it is to make sure the screen is plumb, I then take a measuring tape from the green tube center dowel to top corner of screen both sides. The measurement should be the same. If not move the projector to make it the same. I then take a measuring tape to the back center point of the green tube and repeat the process. Rinse and repeat. Then if everything is perfect you should be able to take a tape to the bottom of the screen and repeat the process over and all measurements should be the same for the given measurement on the opposite side. This gives you center of the reference green tube rather than the chassis.
Jim

stefuel · Posted: Mon Oct 20, 2008 10:17 am Post subject:

All of what you've just learned ain't worth a hill of beans if the projector is not at the right height or distance to the screen.

rtart · Joined: 16 Jun 2008 Posts: 132

Curt, Kal,

Maybe this should be a sticky?

jeffslife · Joined: 17 Apr 2010 Posts: 4190 Location: ohio usa

Yes it should.

dvh99 · Joined: 25 Dec 2009 Posts: 2158 Location: nederland

am i missing something here or am i the only one that wants the active image to be centered on the screen?
my raster is shifted towards the left edge on the tube table mounted.

ecrabb · Posted: Wed Nov 10, 2010 7:04 pm Post subject:

dvh99 · Joined: 25 Dec 2009 Posts: 2158 Location: nederland

because the active image and the shifting towards the left edge isnt discussed here and the fact that this thread doesnt contradict this persee doesnt mean that this not remains unclear to some.

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

Centering the raster on the tube is a different operation from squaring the PJ to the screen.

If your PJ is square to the screen, AND if the center of the green lens is exactly centered on the screen, then a centered green raster should hit the screen in just about the right spot.

If the PJ is square (using the techniques here) and your green raster is centered, but the image is offset on your screen, that indicates the PJ is not centered on the screen. Move the PJ or the screen. If you can't do either, you'll have to run the raster off-center.