Projector, image sloping on top..

[Anderzz]

Top part of the image slopes from left to right and i dont understand why...

the bottom is square and fine, but the top is sloping, lower on the right than the left.

Currently with a limited throw my image is 30" high on the left side, and 29" high on the right.

I cant find an option to correct this.

Projector is an hd65

any idea?

[stevelup]

You haven't got it square to the screen - it can't be anything else!

Steve

[Anderzz]

Im pretty sure its square, surely if it was out, it would throw out the other sides?

the image is focused etc, ive only recently noticed it.

Im not home right now, but im sure as hell the projector is sitting square facing the wall.. hmmm

[stevelup]

You need to think in multiple dimensions! It's quite tricky accurately lining up a projector.

At the moment, your image is bigger on the left than on the right. That suggests that you need to (ever so slightly) rotate the projector (looking from the top or bottom) to the right.

Once you have the image the same height at the left and right (by rotation only), you may then need to straighten the image again by rotating the projector slightly (looking from the front).

Once you have done this, you need to measure the width of the image at the top and bottom. If one is wider than the other, you will need to tilt the projector (looking from the side).

Each time you make a change in one dimension, you will need to recheck all the other ones

Steve

[27neth]

Hi,
I have the same problem. The picture is fine on the top but slopes on the bottom. I have had a spirit level on the screen and the projector but its got me puzzled....

John.

[stevelup]

You can't really use a spirit level to do anything other than the initial setup because any tiny error will be magnified by several orders of magnitude once the image gets to the screen.

Also, a spirit level won't help with issues where the projector is rotated in the horizontal plane.

Try following my instructions above - the important bit is to get the horizontal rotation right first (make sure the image height is the same at the left and right) before doing anything else otherwise you are on a hiding to nothing!

Steve

[Anderzz]

Thanks for the explaination steve, but im still miffed.

The way i see it, if the projector is projecting closer on the left than the right, then the image on the right will be narrower on the right, causing it to slope up at the bottom, and down at the top.

I dont understand how it can be a 90º angle on bottom left, but on top left its not. surely both would be out

i dunno lol.

i tried moving it about but had no luck, but i never did it to the extent you mentioned.

[stevelup]

Ah yes - you are quite right. But...

If the projector is rotated slightly to the left, the image on the right will be smaller than the left - agreed?

Now, what if the projector is also not quite level - pointing down towards the bottom right hand side for example. What you will now have is a bottom edge that is perfectly straight and a top edge that slopes down to the right.

As I said, it's the combination of all the different angles that make for a square image.

You have the following adjustments:-

1) Horizontal Rotation (clockwise / counterclockwise when looking from above / below)
2) Vertical Tilt (clockwise / counterclockwise when looking from the side)
3) Rotation about the axis of the lens (clockwise / counterclockwise when looking from the front)

All the above relates to getting the image square and has nothing to do with the position of the image on the screen. What you should do is get the image perfectly square first (irrespective of whether it is hitting your target area or not). Only when you have done that should you move the image to fit the screen using lens shift.

If you don't have both horizontal and vertical lens shift, and you have a square image but it doesn't fit the screen, the only option you have available to you is to physically move the projector - at which point you will need to start from the beginning!

Steve

[Anderzz]

Ah ha!...

maybe its sloping down and to the left, causing the top right to get a bit closer, seems like it could be it.

if it turns out i cant get it sorted, whats optoma like for returns, i bought the projector second hand but have the reciept and its only 1month old

[stevelup]

I can't answer your question about the return. I can guarantee you though that it is not the projector which is to blame

It really is surprisingly difficult to correctly align a projector especially when you haven't got lens shift.

Steve

[Anderzz]

The thing that has me miffed is that i plonked it on the desk and aimed it at the wall, and it was fine, then i unhooked it, put it away in corner for a while...

hooked it back up on same desk and now im noticing this, its strange, but since im at my mams house now i cant try, but ill give it a go tonight.

cracking projector though

i see RBE at times, but i think my brain has learned to ignore it. i dont get headaches or anything

[stevelup]

If it's just sat on a surface pointing at a wall, then I'm sure you won't have any problems. Just twist it to the right a bit and it will be fine.

The difficulties arise when you are trying to aim it at a screen. You've got it easy at the moment

Steve

[Gary Lightfoot]

stevelup is right. If the image is smaller on the left than on the right, that part of the lens is closer to the screen than the other side, hence the other side is bigger. You need to physically move the pj to the right (as little as half an inch in some cases) and rotate it to the left to realign the image with the screen.

If the pj is projecting from the ceiling, the slope will be on the bottom but be straight everywhere else. If it's table mounted than the top will slope instead.

Moving the screen is another option if that's more convenient and then you just have to rotate the pj and not necessarily move it.

Gary.

[KpjComp]

I know I'm pointing out the obvious here. But just in case, have you checked to make sure the digital keystones are both set to 0?.

[Anderzz]

I dont know if you understood what i meant guys...

The image was smaller at the top right corner, whereas the rest was fine.

Keystone makes the image a trapezium shape.. the pic wasnt a trapezium, that would mean it would be symetrical on both sides. Mine wasnt. It was sloping on top from left to right, but perfectly straight from left to right on the bottom.

Anyway with a bit of fiddling last night i improved it a bit, but its not 100%.

Once i get a ceiling mount sorted it shouldnt be a problem