Been working on my first projector install these last few days, and overall it's gone fairly well (I was as surprised as anyone when my measurements to align center of proj lens with center of projected area came out ok!).

One nagging question, though - how do you folks ensure that the projector lens is exactly parallel to the projection screen/wall?

I was considering using a horizontal & vertical laser level on the top & side edges of the projected image to ensure that the top is level and sides are plumb ... presumably if the proj is not || to the wall then there should be some minimal horizontal keystoning detectable with the laser level/plumb - thoughts on that?

Any other suggestions/tips?

I usually measure from the side wall to the center on both the screen wall and for the projector. I also almost always use a cheif RPA-U mount which will then give me some play to move the projector side to side if I'm off a little bit.

its been years since i've done a projector install, but what i used to do would take a 2 centerline marks from the screen to a position close, but in front of and then another behind the projector. to do this, i would use a piece of string. just like in geometry, if you want to find the mid point of a line, you make 2 intersecting arcs on 1 side of the line, then make 2 more intersecting arcs on the other side of the line, then use a straight edge to connect the arc intersections, or bisect the line... exactly at its midpoint.

the concept is the same here, except you are forced to make all arcs on the same side of the line (screen) and use different lengths of string to give you 2 discreet points.

this method eliminates all other things that could come back and bite you, like the room not being square, the screen not parallel to the wall, the projector housing not being square / perpendicular to your reference, etc...

of course you should confirm your final placement with a test pattern and measure for keystone.

if you got them, those rotating laser levels do the same job, but don't make you look like an amateur with your ball of twine.

Took me a few minutes to work out what you're saying, and I still only understand the first part (bisecting a line w/multiple arcs, MAN it's been a while!) ... still have to reread your post several times to see if I can grock how this translates to the screen/proj calculations.

Re: the laser, though - I'm going to try that out this AM ... I have a Pacific Laser PLS2, hopefully it's horizontal level and vertical plumb projections will do the trick...

I use a laser quite often but mostly to make sure I am on center of the screen. If your projector is not parallel with the screen you will see keystone distortion. You can usually see this right off but if you want to be sure, simply measure your image with a tape measure.

If you get the center of lens and center of screen perfect, then the projector will be square to the screen when the image is centered in the screen. ;)

I tried the laser, and went back to old school as mentioned above. String (or CAT5 lol) and a pencil. Make 2 bisecting arcs and center the lens on the screen. Seems caveman-ish I know, but it works everytime.

Its also nice to use projectors with horizontal and/or vertical lens shift. ;) Fudge factor is always nice.

One thing I learned at Runco Academy was NEVER USE KEYSTONE ADJUSTMENTS! Screws the resolution and geometry.

You mount the screen where you want it, and you put the projector where it needs to go height-wise (look in the manual for offsets). Mount the projector so it is level and center the lens on the center of screen. Calibrate. Done.

PS netarc it's grok

If you're going to use obscure Heinlein references, at least spell them right so's a body can google them...;)

Interesting trick...guess I forgot my geometry.

I always worry about the side walls being exactly 90 degrees to the screen wall. If one were to measure from the same side wall but the angle of side wall to screen wall was off 1 degree or the builder didn't plane his studs after the framer used twisted pieces of crap you could be off. I mount the screen... measure to the center of it. Then I break out my square (36") and make a few tiny marks along the side that juts out. I then put my little 39.00 Home Depot laser unit on the ceiling and project it along my square line. I get the lens smack dab in the middle of the red and rarely have more than a tniy adjustment. Always open to better methods though.

Keystone adjustments are for teachers showing slides or corporate suits with Power Point Presentations.

Sounds like a good trick, and better yet reliabled ... can you detail a little better how you use the square to make the "tiny marks along the side that juts out," I think I understand but am having a hard time visualizing it.

The shorter end of the square goes along the top of the screen. Right at the center mark you extend the long end to touch the ceiling and make a couple of tiny pencil marks where that spot is. You'll most likely need a level to get the center mark to the ceiling. Now lay the square or other straightedge from that mark to the extended one you made and make a few more little marks along that line. Put the back edge of your laser against the ceiling and make sure your line follows the marks. I've had a screen off kilter enough that the rear measurement to the center of the lens has been off by almost 4 inches! (I probably should have shimmed it out but I thought that might look weird).

You guys make me laugh most of the time. In the production world where I work you may install 5 projectors in a week, all of these lines and measurement will not work. You normaly dont have 3 days to mount a projector. You should make sure the projector is installed in the center of the screen, The biggest problem I always face, is the throw angle correct and can I fix it if it is wrong. Good projectors always provide a chart which will tell you how much play you have from the projector to the top or bottom of the screen, meaning how far does it hang from the ceiling to hit the screen properly. Find a projector that allows you to adjust the up and down and side to side alignment. Note to self. Many projectors can allow for all of these adjustments, but at the expense of picture quality. Yamaha, Sony and Runco are 3 that I know will allow for adjustment with degridation of the picture unless I was a total idiot when mounting the projector. Throw distance is also a common mistake. I like to get the projector as close to the screen as I can so I dont have to expand the picture out any further than necessary. Again, the manufacturer includes a chart for this. Mounting it as close as you can will give you the best picture. I always like the electrician who has no idea where the projector is going and just installs the outlet in the corner or doesnt install one at all. It all comes with experience and after you mount the first 100 or so, you will get it.

I always like the electrician who has no idea where the projector

I don't rely on an electrition to get it wrong, I run romex along with the interconnects to use as an extension cord to the surge protector. Keeps the ceiling clean.

....And I would imagine it keeps your install in code violation as well.

skyflyer...

It never takes me more than an hour to mount a projector... I donlt know where your three day assumption comes in. Hey... my method gets me close enough to use minor adjustments that the best mounts come with.

As far as the romex... thats OK with code. Check out panamax MIW-Power Kit. Hook your projector up this way to an APC UPS and you'll save your bulbs and get it in line with the surge suppressor... just takes a little minor planning.

Most projectors will give you the best picture at the back half of the throw range. If you mount the projector further from the creen you are using the better part of the lens.