I finished assembling my projector today. The quality of the picture is amazing, i can get almost the entire LCD to be in perfect forcus. However, its really dim. With the lights on low in a basement room at night, the image isn't visible at all. With all the lights off, its pretty clear but there is a very obvious hotspot in the middle. I checked all the measurements, made sure the fresnels were in the right way (220mm in the back, 330 in the front, grooves facing each other.) but I still can't determine why its so dark. I see lots of pictures on the forums of people using their projectors in the middle of the day. Tis all gettting somewhat depressing

Specs:
Standard LL lesnes,
SD400 lamp
BenQ 557FP
nVidia 6800

Pics:

the build

bright spot (projected onto blackout cloth)

good image quality

Try sealing off all the light leaks coming from your box. It could be the leakage is overpowering the projected image.

Al

I don't know if its a misprint but it should be 330mm at the front. If you are not far anought it will cause the light to be dimm

That open front will be killing it. Seal it up, get a reflector and try moving the bulb a bit closer to the rear fres (or away, whichever makes a difference!)

The front was closed when I took the results pics... Just opened it up to check some stuff inside.

i havent made my projector yet, so im speaking from no experience, but shouldnt the grooves on the freznels be facing away from each other? the 220mm groves should be facing the bulb and the 330mm should be facing the triplet. please correct me if im wrong.

Grooves face the LCD.

GlassX, Look at the back of the triplet while the projector is running and see if the light is going through the triplet or hitting off to the side. That hot spot shouldn't be there either, are you SURE you have the fresnels in the right order? If so the lamp distance is very wrong.

Thanks for your help everyone! It tuns out i was just using the projector too close to the screen. moved it so it was about 7 feet back and it was MUCH better. The image is still a tad dim, but i re-measured and the bulb is about 1 cm too far back, and i still need a reflector.

also remember to move your lamp back and forth like ozstang suggested..for me my best eveness of brightness is about 7.75 inches, arc to rear fresnel

1) Like Brain said. Make sure you the light is hitting the triplet. The best way to tell is to hold a piece of paper behind the triplet. This makes it easier to see.

2) Once I had everything aligned the next most important thing for me was to be able to move the bulb closer to the fresnel. It looks like you have screwed the mogul base into the side of you box. To be able to move the bulb you might want to cut a horizontal channel in the side of your box. That way you could loosen the nut on the mogul base and slide it forward and backwards while the lid is shut and it is turned on. This would enable you to tweak it as needed. That is of course the quick and dirty method. You could also build a sled for the bulb to slide in.

Dear GlassX,
I have built the projector after study of various designs and contents of forums and evloved my own design of enclosure. The arrangement is that all the parts like fresnel lens, LCD panel, MH bulb with reflector and the projection lens can be adujusted with precision from the front of the enclosure. The projector is mounted at a ceiling height at a distance of 20 feet from the wall screen. The results are excellent. My experience is that all the elements need fine adjustments.

Oh. I thought it had to be dead on the focal length of the rear fresnel :-)

Thanks, gunna try that as soon as I get my drill back.

no it doesn't, generally people find its better if its a little closer that the Fl of the rear fresnel, maybe .5 - 1"(so like 200 mm or so)