CurtPalme.com Home Theater Forum

[budk]

I believe I have this right but I wanted to verify it.

I have a 1208s/e and I'm in the final stages of building my theater. I used Barco's LENS program and selected 1208s/2 from the discontinued menu and I entered in the screen info. The program calculated a ceiling distance of -7.70.

I assume that this means that in order to get the image projected even with the ceiling that I would have to mount the projector 7.7 inches into the ceiling.... and if I were to mount the projector flush on the ceiling then my image would be 7.7" down from the ceiling. Am I interpretting this correctly?

In my case and if I am figuring this correctly, I will want to mount my projector about 6" from the ceiling which will put the top of the image at approx. 13.7" from the ceiling.

I just need some confirmation before I start building my soffits.

Also, how much room is there for error? I'd like to mount the projector a couple of inches higher and angle it slightly down. Are these projectors any good at keystone correction?

Thanks. Bud

[VideoGrabber]

Bud asked:
> Am I interpretting this correctly? <

Yes.

> how much room is there for error? I'd like to mount the projector a couple of inches higher and angle it slightly down. <

Well, you'll already have some error, if you're relying on the LENS program to get the PJ distance to achieve a specific screen size illumination. To maximize raster use (and light output, minimize wear, etc.) you'll want to go closer than LENS says. That's why Kal always advises setting your rasters first, then move the PJ around on the floor/cart to determine best PJ to screen distance, THEN selecting a mounting point.

When you move the PJ closer, there's less drop, so you'll need to move the PJ even lower than planned. So there's a cascading effect from blindly following LENS recommendations.

> Are these projectors any good at keystone correction? <

Yes, but keep in mind that they already have 10.5-degs of correction designed in. When you say "angle it slightly down", a lot depends on how slightly. It may not seem like much more to you, but it could to the PJ. An extra degree or two is probably OK, but 5+ is pushing it. Additional angling drop results in: greater keystone, reduced max scan-rate capability, more scheimphlug compensation, and generally more futzing with geometry and convergence. Worst-case, excessive angle can make it impossible to achieve good image characteristics (the "problem-corner" you can never get quite right, etc.)

That said, folks usually do what they need to do to fit their constraints, then deal with the consequences.

[rod]

when I first got my barco back in 2002 I asked the exact same question. I always believed that pgms like Lens would be accurate but I realized after much trial and error that by far the easiest method is exactly how it is described above. Project an image at your preferred resolution, maximize raster use, and move the pj until you fill the screen. easier - do it on the floor and take the measurement. that works 100% of the time without fail. I had the negative amount as well but I was ok because I had a sunken ceiling. Your screen width must be close to 96" because I recall my ceiling height to be around that.
As for the keystone I mounted 144s and that pushed the pj 4-5 inches closer. I had forgot to also adjust the height and I simply corrected by angling it. Keystone is to the max and I do have the right upper corner screwed up but only 1 inch high by 5 inches across. I never see it unless really looking at it. I'll likely adjust at some point but right now I'm happy just watching.

[budk]

Thanks guys.... At least I know I'm in the ballpark with the lens program and I can do as you suggest when the time comes to figure out the exact mounting.

thanks again.... more questions in a few weeks/months.

Bud