Screen drop and projector drop help needed.

[mnfish]

I just need a little help on figuring out what is the best way to measure the drop from my ceiling that my screen needs to be? And is there a certain drop the projector needs to be to get the best image? I have 8' ceilings. I have a BenQ W5000 and will (most likely) be installing a 110" 2:35:1 screen (50"hx108"w OD). I think I calculated that the throw will be 18'6"? Or somewhere in that neighborhood. And yes..I will be using an anamorphic lens. The BenQ has a v stretch mode for it.

[mnfish]

Any help?

[Beta Man]

plug the info in here..... and it will show the distance from the ceiling for the projector, among other things.

http://www.projectorcentral.com/proj...calculator.cfm

[mnfish]

Beta Man Thanx for that info. I've tried that one before but it doesn't give a 2:35:1 calc and doesn't give a floor to top of screen height in relation to projector height. Does the screen height need to be at the top of the screen height?? Middle of the screen? I want to know what is the opimum placement of the projector in relation to the screen?

[Beta Man]

I believe you'll want the lens "Dead Center" of the screen..... so mask out and measure where you want the screen, measure to the center, and that's how far from the floor you'll want the projector to hang........

[Brain Sturgeon]

Originally Posted by mnfish

Beta Man Thanx for that info. I've tried that one before but it doesn't give a 2:35:1 calc and doesn't give a floor to top of screen height in relation to projector height. Does the screen height need to be at the top of the screen height?? Middle of the screen? I want to know what is the opimum placement of the projector in relation to the screen?

You never use the width of your 2.35 screen in calculating throw ratios-- you figure the throw ratio based upon the width of your 16:9 screen using the same height as your 2.35 screen.

As far as optimum placement of the projector, most installers recommend lining up the center of the projector lens with the top of your screen, dead center to the screen, and then using your vertical lens shift to shift your image 1/2 picture height to fill your screen correctly. If you have the ability to place your projector lens lower than that, down to as low as the center of the screen, that would be fine also, although that placement is usually more problematic as peoples' heads and the tops of seating/furniture may start to get in the way of the light path.

[mnfish]

SI has a calculator, too. You can change the ratio of your screen there?? But it doesn't do the projector throw. I guess it's best to just project it on the wall and mask it out like Beta Man said? I could just make the screen and back up the projector until it fits the screen at 2:35:1? Then mount it? I have the luxury of doing that. All my wiring will be done after I get all my dimensions correct.

http://www.siscreens.com/calc/calc.p...=500&width=810

[mnfish]

A little change in the subject but I'm using a BenQ W5000. It says it has 1200 lumens. Would that be bright enough to light up a 110" screen?

[Brain Sturgeon]

That SI calculator won't help you with planning your projector placement.

Just use the calculator for the BenQ W5k @ projectorcentral:

http://www.projectorcentral.com/BenQ...calculator.htm

I'll throw in some # for you:
Your 110" 2.35:1 screen is 46.81" tall. That would make your 16:9 screen 83.22" wide or 95.48" diagonal.

The zoom on the projector is 1-1.2x, so the throw distance you can place the projector at are from 12' 9" to 15' 4" (throw ratio of 1.84 to 2.22). So your throw of 18' 6" won't work for your screen size and projector combination. You will have to (a) move the projector mount closer, or (b) change to a larger screen size, or (c) change to a projector with a long throw lens. At a throw of 18' 6", the smallest screen you could use with your projector is a 100" wide 16:9 screen (132" wide 2.35:1 screen).

You can play around with the calculator a bit more to see what will work best for you. Getting some numbers that will work for you is a good start. Then you can fine tune placement by throwing an image up on the proposed screen wall and use painter's tape to mask out your proposed screen area.

In terms of brightness, 1200 lumens output would get you ~33.5 fL on a 110" wide 2.35:1 screen @ unity gain (=1). That's pretty darn bright. However, be aware that the reported ANSI lumens spec on projectors is almost always much higher than what they actually are, particularly in "best viewing" mode. From this review: http://www.projectorreviews.com/benq...erformance.php , the W5k puts out a max of 670 lumens in "Cinema Mode" and 1270 Lumens in max brightness mode. Brightest mode will usually give you a poorer picture, but everyone will be different in terms of what looks good to them (picture quality and brightness). It seems that the projector has a number of options so that you can adjust it to your liking. At 670 lumens, you would get 18.74 fL on that same screen. Acceptable brightness, although a lot of people are shooting for 20 fL these days.

Also keep in mind that the lumens output will decay over time as the lamp ages. Some reports have measured about 30% loss of brightness over the life of the lamp, although this seems to vary from projector to projector.

Hope this helps!

[mnfish]

Hey guys, thanx for all the help! It is greatly appreciated. When it comes time to start the project I will post pics on the progress.