I posted this in technical support, but it hasn't gotten any attention, so I guess it's more appropriate here.

Okay, so I have the standard ultra basic set up:
Elmo A305 projector (575W MH) with reflector and pre-con built in
15" LCD sitting on a frame about 1.5 cm off the fresnel's.

When I project, I'm getting wash out on the bottom half of the image when videos play (noticeable in dark scenes). It's not light leaks, as I have sealed off everything, it's more of an overall over-brightness. This happens with the my overlay video settings at 130% brightness. With regular 100% brightness, the bottom half is fine, but the top half is over-dark, it almost looks like the inverted blacks of a TN LCD panel viewed off-angle. So really, it's some sort of light imbalance on the bottom half of the LCD.

The last weird thing is that it doesn't seem to be a problem on non-video material, i.e., when I view the windows desktop before launching a movie. It could be just that it's not that noticeable except in dark scenes, though, so I wouldn't put much stock in this.

Any ideas? The overhead i'm using arrived slightly damaged, so it's possible that the reflector is out of alignment, but from what I've read, that results in vignetting/hotspots, etc...whereas this is literally the whole bottom of the LCD seemingly getting more light than the top half.

As I mentioned, it almost looks like a TN panel viewed off axis, but how could that be, given that it is directly on-axis? I don't have another panel to test with, although I will have another in a month or so if completely necessary, but I don't think that is the problem.

Any thoughts would be much appreciated.


EDIT: 6 pages deep in a google search, I found this: http://www.lumenlab.com/forums/index.php?showtopic=10709
which is sort of a similar description to my problem. Still no idea what's going on with mine, though, since my LCD was fine before, the polarizer is untouched (haven't attempted any AG removal), etc...

Most likely the light needs to be move up/down just a bit.

Or since it's an overhead I guess it would be forwards/backwards or left/right depending how you are looking at it

So for example, the light being moved an inch to the right could move the entire light distribution into line?

Interesting. I don't know if I can even do this, since everything's bolted down, but I'll see what can be done.

Thanks.

Yes it can.

Most likely the fresnels are misaligned a bit off center. But since the only way to fix that is to buy new fresnels I suggested moving the lamp because it would fix the problem.

Makes sense. It's possible the fresnels were out of whack due to the shipping- it came a little bit busted up.


Thanks again.

As far as I can tell, I really can't do anything to move the lamp. The OHP light box is all metal and put together very solid, which begs the question of how the lamp got off-center to begin with!

Is there any other piece I could try moving? If moving the fresnels up and down (not depth wise) can help, I'd like to know before I try, because I don't think it can be done without some modification. But it would be a lot easier modification than hacking apart the metal light box.

I guess this is what I get for trying to take the easy road with the projector


Thanks.

The principal axis of a projector is the line that connects the lamp, center of the fresnels and center of the projection lens.

Moving any of these elements will result in problems, however, regardless of which one is moved, you can move any other to get things back to where they should be.

You can try to move the lamp, though that seems to be difficult based on what you way.

You can move the fresnels, so that the center of the fresnels is directly between the lamp, and triplet.

You can move the triplet, so that it's in line with the lamp and fresnel centers.

Moving any of these three elements will bring the principal axis of your projector back into alignment. (Is it possible that the OHP head was bent? That would move the triplet out of line from the lamp/fresnels, and is probably the most likely thing to move.)

Oh, I had not considered that. It is definitely possible. I think the overall frame got a little busted.

Thanks for the suggestion. I will try it tonight.


Also, I found that with ffdshow, you can overlay a bitmap (somehow i missed that option before). So worst comes to worst, I can overlay a gradient and compensate. But that's hardly ideal.


Thanks again.

EDIT:

It's going to be tough to move. I will be inspecting further tonight. Strangely, my poking and prodding yesterday seems to have shifted the light pattern a little, although that may be my imagination.