Hi, Im kinda new to this, but my projection project involves the use of an overhead projector, and a Sony Hi Def Portable Widescreen LCD dvd player. (8" screen has been removed from it's factory enclosure and placed on the overheads viewing bed) The picture is projected onto a 8 ft screen and is of pretty good quality, but if I increase the contrast control to allow all of the dark objects to be seen, then the lighter objects become washed out into just plain white.

Does anyone know of a device used to further control the pictures contrast? Like a compressor that prevents light images from washing out, and becoming solid white, or dark images from becoming solid black?

Default conrtast really should work, however, there will be an issue if there's a lot of light in the room, or if you aren't masking off the light from around the panel. In that event the relatively dim light going through the panel is going to get washed out.

LCD panels block 91-96% of the light that hits them, allowing only 4 to 9% through -- and that's on the white areas. If you have light that doesn't go through the LCD, then the dark areas will be hard to distinguish from black.

OK. Well, I have done a fairly good job at cutting down on the light that does not go through the panel, but perhaps not good enough. I purchased a window darkening shade made to eliminate light from coming in a window, and I cut it and wrapped it around the OHP. I estimate that this cuts down on about 90% of the light that does not go through the panel. The other 10% can and should be eliminated though. I will work on that.

You did inspire some thought just now. I wonder if the window darkening material that I am using could be causing some problems because it is made of a white reflective type of plastic? Light can not go through it, because it is 100% opaque, but it could maybe be bouncing stray light around and eventually up through the focal lense. Do you think that would give me a washout effect? I'm guessing yes. Maybe I could glue some black felt material to the window darkening plastic.

I am still curious about the possibilities of an electronic contrast compression device. Do you know if such an animal exists? If not I will just work on eliminating the stray light.

By the way, I really appreciate your help.

Listen to him. For he is wise and all knowing! I tested it just to see what the number would be: HERE IS THE WRITE UP IN MY PLOG

I was amazed at how much of the light the LCD blocked.

Also some Lcd's just have plain ole bad contrast.

I've had some that looked washed out with gray blacks no matter what you do.

Not all Lcd's are created equal.

This might help, not sure in your case. Input is thru VGA

http://www.curtpalme.com/Box1021.shtm

Yes, I agree he is very wise. He is correct in diagnosing my problem. I had entirely too much light coming from around my lcd panel. Once I properly masked off that light, the dark areas became more visible. That light was interfearing with the darker details on my picture. It is that 4 to 9% of the light that is all that we are trying to produce distinctly. It takes great care to get your projector to produce ONLY that 4 to 9% .

I'm a happy camper now guys!

Thanks also for the link. It looks like what I was asking about. Unfortunately, I don't have a vga input.
I really don't think I need any additional devices after all. Blocking the remaining stray light has made a tremendous difference.

Thanks again to everyone.