Hi


I'm planning to build a 1080p projector (using a wuxga 15,4) and I'm trying to get a screen around 100 in. I am concerned about the quality of the projection if I use a standard triplet from a distance of 10 feet. Do you think the quality on the screen will be the same?

Thx

The standard lens is a good quality optic. Your screen image should be fine. Do you really want a 131" diagonal screen, or would you rather have a more reasonable 78" screen?

80" diagonal is good to me, considering that I am currently using a 20" CRT tv.

So, I'd go with the Pro triplet and pro fresnel... but, maybe, let's say that I want to have 10 more inches, is it a good option to change the fresnel gap (front fresnel and lcd) from 20mm to 100mm, without disturbing the quality? (Yes, I know, I'd need to change the lcd distance too...)

Thx for answering this fast

With the pro lens, I'd design for unsplit. (By the way, the standard fresnels won't fit with the 15.4" widescreen. Forgot to mention that.)

But the pro lens and fresnels will do a really good job with the 15.4" screen.

If you really want that extra 10", then I'd look for ways to back up the projector a little. Maybe go with a folded design.

Oups... didn't see that coming too

Anyway, I was already planning to go for a folded design since it's going to be over our head while we'll be watching the movie.

Why would you go with unsplit? I heard that the blacks were not equal and....

HERE COMES THE NOOB QUESTION:

EDIT: Using the FocalCalc and an UNSPLIT fresnel, considering that I'm using the 15,4, pro fresnels/triplet, distance of 10 feet and a screen of around 78", am I suppose to find the distance LIGHT-(1)>Fresnel-(2)>LCD just by tweaking or there is some form of calculation?

Thx again SupraGuy

the distance between the light source and the first fresnel depends on the FL of the fresnel. Say you have a 220fl first fresnel, this would make it roughly 220mm away from the light source, this will take tweaking and may in fact end up closer or father away from the light source, thats why people make their lamps adjustable. The distance between this fresnel and the lcd should be small, 10-15mm is what I use and it seems to work fine. Good luck!

Unsplit delivers a slightly better picture overall, however, particularly on the 10.6" panels, people have noted "glowies" in black screens because the light is no longer collimated. This is also generally with shorter FL objective lenses, so the angle also tends to be greater than it will be with the pro lens. With the pro lens, because the distance is greater from LCD to triplet, the angle is also closer to the collimated perpendicular. This will be enen more so with the 15.4" LCD vs the 17" LCD, so I don't know that I'd anticipate any major problems there.

With my build, I do notice "glowies" around the edges on BLACK screens, however, the effect goes away, even on very dark screens

the following is from my PLOG:


This is the "weathertop" scene from Lord of the Rings which is very dark. At even this level, the "glowies" are all gone. The only time I see them at all is if the screen is BLACK. They don't even show in the black bars top and bottom when the movie is letterboxed.