I have been working on my setup for the last couple of weekends now, and I must say I am a little disappointed in the brightness of my projector. I am using a 400w bt28 metal halide with a eliptical reflector made out of a sheet of curved aluminum. The thing is really bright without the lcd in place, but when I put it through the lcd panel it seems like about 10% of the light gets through. I do have a clear image but not very bright. Im using a fresnel from a 3M 9000 series OHP. I am also using 15" I-O Data desktop LCD and I have my made my own box for it all. I am wondering if anyone here has found a better kind of reflector than the eliptical one Im using. I have also tried several types of screens but none seem to help that much. Sorry for the novel but this thing is on my mind right now, Ill try to get some pics up in a day or two.
Your problem is likely because a LCD is only capable of passing polarized light. When you have an eliptical reflector the light is bouncing all about and typically about 10% of the light gets through the LCD... this has been discussed at length in many threads around the forum.
Well, as I love to do these semiscientical calculations of mine...goldmoth said:
You say that the image that you get is not very bright... ok... the I'd guess about 100-250 lumens max output in the end.... so....
400w bt28 metal-halide = about 35000 lumens
200/35000=0,0057 = 0,57%
So... 99,43% of the light has been lost somewhere. Sounds damn lots to me but believe me, if your image would be anything like even produced by final output of 400 lumens or so you would be satisfied, you would not call it "not bright", so this really is the truth. Either the reflector really sucks (it does not reflect any light from sides of the lamp, it's not reflective enough or something like that) or the lcd you are using is really quite no good for projecting purposes.
Regards
HB
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