[William Mapstone]

This may be a silly question, but I had a salesman tell me that the projector should be as close to the screen as possible to optimize light output. In other words, the lens would be zoomed out as much as possible and then you would place the projector at the point where you reach your desierd screen size. (this ofcourse assumes that room layout allows this) Is this true??? My guess is that it wouldn't matter.


-By the way, I discovered this web site a couple days ago, and must thank everybody for the helpfull information and interesting topics. I wish I knew about it 2 years ago when I started building my dedicated home theater room.

 

[mblank]



The light output of the projector doesn't change, of course, unless you believe in magic.


However, the brightness of the image is proportional to screen area (i.e. width x height). So your dealer is correct in saying that a smaller screen will display a brighter image, all other things being equal.


You can calculate the brightness of the image in foot-lamberts as follows:


FL = Light Output (Lumens) X Screen Gain / Screen area (sq.ft.)


You'll get a variety of opinions about how bright is "bright"; movie theaters use something in the 12-13 range, but home theaters can go brighter.


If you search the "Screens" forum, you'll find a lot more.


- Marc

 

[mflaster]

It sounds to me that the salesman was saying that for the same size screen, if your projector has a variable zoom lens, you want the projector to be as close to the screen as possible.


If you have a lot of fog in your room, that's probably true... http://www.avsforum.com/ubb/smile.gif


Mike

 

[steve5097]

Actually, the light output really does change, because the effective f# of the system changes, as does the magnification. That said, it is a second order effect, and a small one at that.



------------------

Steve

 

[mblank]



Yes, well. I was responding to what the salesman told the original poster - I doubt he was thinking of second-order effects. I doubt that he was even thinking.


- Marc