Perfect alignment?

[PC_112]

Hello,

Does the projected image align perfectly on your screen?

I have a screen hanging from the ceiling with black borders and I am trying to align the image perfectly on it, but I am always missing about 5 millimeters on one side or another. (e.g while on the right bottom side the projected image touches the black border, on the right bottom side it is about 5mm inside the black border - the screen is 203 cm wide)

So far I am just moving the projector and using lens shift in order to align it. Should I also try to use keystone, or I shouldn't bother? I can only notice that is not perfectly aligned when I go close and because of the black bars on the screen that I am trying to align it to.

[gingerone]

I would stay away from keystone at all costs, it will ruin your picture. I'd overscan the picture just slightly in to the black.

[Nick_UK]

Originally Posted by gingerone

I would stay away from keystone at all costs, it will ruin your picture.

That is a very broad statement. Surely it depends on the projector ? I use the keystone correction on my Benq 6200, and it does not "ruin the picture".

[Gary Lightfoot]

If one side slopes down in a corner, then the projector is too far to one side.

If the image is lower in the bottom r/h corner, then the projector is a little off center to the left, so moving it to the right (try an inch to start) should level it up.

What you have there is horizontal keystone - with the projector a little too far to one side, the left of the lens is nearer to the screen then the right, because you've rotated the projector to the right to line the image on the screen.

HTH

Gary.

[PJTX100]

Originally Posted by PC_112

Hello,


I have a screen hanging from the ceiling with black borders and I am trying to align the image perfectly on it, but I am always missing about 5 millimeters on one side or another.

At the screen sizes we are dealing with I'd consider 5mm to be within tolerance. As you say you'd barely notice it...PJ

[PC_112]

so moving it to the right (try an inch to start) should level it up.

My prjector has horizontal and vertical lens shift. Is doing some horizontal lens shift the same as moving the projector to the right?

[PJTX100]

Originally Posted by PC_112

My prjector has horizontal and vertical lens shift. Is doing some horizontal lens shift the same as moving the projector to the right?

No. Horiz lens shift keeps the image dimensions static.

"Moving to the right" is better described as "swiveling to the right" which will have the effect of making the right vertical edge longer and the left vertical edge shorter. Tolerances here could be fractions of mm's!..PJ

[Gary Lightfoot]

I actualy meant physically moving it to the right and not swivelling, because the position is probably wrong and swivelling is what is probably causing the problem.

Keystone might correct it, but I would prefer to get it correct by positioning if possible.

If it really is that small and un-noticable from normal seating distance, then it might be easier to do as others have suggested and use the black border to absorb some overspill if you make the image a little larger to hide the gap.

Gary.

[PC_112]

"Moving to the right" is better described as "swiveling to the right"

ok, but if I swivel to the right wouldn't that skew the other sides also?

Tolerances here could be fractions of mm's!..PJ

I noticed. I didn't find a good way to do it yet with the ceiling mount. If the screws are too loose it moves a lot. If they are tight you have to force it to move, and in that case it usually moves a lot again. I guess there should be some middle of the way where the screws are tight but not too tight?

[PC_112]

I actualy meant physically moving it to the right

Ok, and just to be sure I will be trying the right thing, when you say "right" is this the same direction in both projector and screen? Ot it is the opposide because when I look at the screen I am turned looking to the east and when I look at the projector I am turned looking to the west?

[PJTX100]

Originally Posted by Gary Lightfoot

I actualy meant physically moving it to the right and not swivelling, because the position is probably wrong and swivelling is what is probably causing the problem.

Ah, yes, see what you mean. I'm probably confusing the issue.

In my defence, it's probably because the way I did it I put the PJ up 1st, got it all square, then put the screen up in the right place.

I'll shut up now!

...PJ

[Gary Lightfoot]

If you're looking at the back of the projector so you can see the screen in front of it, you will move the projector to the right. It doesn't have to be a lot either. I had exactly the same problem with my very first projector so it's easily done.

I think you can do it accurately if you make sure the distance from the top left and right corners of the screen are the same distance from the center of the lens. You can use a piece of string to do this rather than a tape measure.

Hope that helps.

Gary.

[Gary Lightfoot]

PJ,

I had to do it the other way round due to the roofline restrictions in my loft, so the screen didn't have much lee-way for moving other than an inch or so each way (it can slide a bit). Once that was up I had to position the projector.

Gary.

[PJTX100]

Originally Posted by Gary Lightfoot

PJ,

I had to do it the other way round due to the roofline restrictions in my loft, so the screen didn't have much lee-way for moving other than an inch or so each way (it can slide a bit). Once that was up I had to position the projector.

Gary.

Yep, can see that's what the majority do.

Sorry for not shutting up as I promised , but if PC has horiz lens shift (which is effectively the same as moving the PJ albeit you may bring in extra issues like uneven focus if you do it too much... catch breath) then the solution may well be to swivel the PJ slightly to make sure both vert edges are equal, then to use horiz lens shift to line it up on the screen...PJ

[Gary Lightfoot]

That might work.

Gary.