Over the weekend I constructed a Simple 15" projector. I used a Stripped Dell 1503 lcd , standard fresnels
and triplet setup. I have a 400 watt metal halide bulb and ballast as the light source. I have the triplet mounted in a oatley shower drain for focusing mechanism. I have 2 exhaust fans and a larger intake fan forcing air through the top slot over the lcd into the box and out the exhaust. I currently have a metal bowl being held by a small plate hanger that fuctions as the reflector for the bulb.I was pretty surprised when I finally cranked her up and really have little complaints. The only problem I seem to have is the light distribution. I see other peoples simple 15" setups and there pictures look great with even lighting. How do you do it? One question I have is with alignment. If the triplet is shifted up or down slightly from light source and/or lcd panel could this cause the problems I am experiencing?Is there another fresnel option that would distribute the light source more evenly then the one I have now? I almost forgot, I am using the split method with the fresnels. If I tried the unsplit method would I have better results with the light distribution problem? Any input would very much be appreciated. Thanks.

Have you adjusted your fore-and-aft positions of the reflector and lamp yet? A relatively minor adjustment of moving the reflector and/or lamp closer to or further from the rear fresnel can result in a dramatic change on the screen. It is, of course, best to do this in real time (while you are watching the result on the projection screen). For any given setup there will be some optimal position for lamp and reflector and personal taste will also come into play.

Unless you require keystone correction I highly recommend you do not go "split". Or at the very least try it with and without "splitting" the fresnels.

Everything must be aligned as perfectly as possible but from the sound of it your triplet is probably already aligned well.

Adding a lens (aka: condenser, pre-condenser) between the lamp and rear fresnel has been shown to improve light distribution for certain setups as well. There is extensive info on this in the forums.

I too imagine its a problem with the position of the bulb or reflector. First try moving the lamp further away from the fresnel. This should give you better light distribution but decrease overall brightness so its a trade off. Also fiddle with your reflector moving it forward and back as Big D suggested. If the image is only darker on the top and sides, and not the bottom, it could also be a problem with components not being centered. i.e. reflector centered behind the ARC, ARC centered with the fresnel and triplet focal points.

Split works really well for a standard projector.

something to look at.

How much light hits the lens. How much hits the shower drain beside the lens? Is the shower drain blocking any of the light from the LCD to the lens?

If the light is being blocked by the shower drain, then that block needs to be eliminated. This will cause dark sides to your projection.

If the light is too large to hit the triplet then you need to adjust your lamp position. The two fresnels should combine to produce a somewhat focused image of the lamp arc. This is the secondary optics in the projector, and determines how much light there is to project.

Finally, make sure that you have your fresnels in the right place, and correct orientation. The grooved sides of the fresnels face towards each other, and the 220mm fresnel should be closer to the lamp. The 317mm fresnel should be closer to the projection lens.

I have an article in the Wiki Guide for checking that the lenses are the ones you think that they are.

Thanks alot for the lenses ID link....Sure enough I had them reversed. The light in the corners and top is much better. I also stacked them as an unsplit version and results are pretty good but I am not done tinkering and adjusting yet. Thanks you guys for the quick response and great info.