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post #1 of 9 Old 11-01-10, 09:55 PM Thread Starter
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Question How far should I put my projector

Hi everyone,

I got a PT-AX200U HD projector with a 120 inch screen. I want to mount the projector on the ceiling. What would be the optimal distance ? I was thinkiing about +- 15 feet away from the screen.

Thank you!
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post #2 of 9 Old 11-02-10, 07:15 AM
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Re: How far should I put my projector

Fifteen feet would be good. I wouldn't go back any farther since that will reduce your brightness. You can mount it anywhere from 12'1" - 24'6". At the closest distance you would have 23fL and at the farthest distance you would have 9fL.

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post #3 of 9 Old 11-02-10, 07:02 PM Thread Starter
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Re: How far should I put my projector

Hi Mechman,

Thanks for the answer. Only thing is I am farely new to HT and not sure what you mean with 23fl to 9fl.

Would you suggest to put my projector closer ? If yes, how close.
Also, how many inch from the ceiling should my projector be ? I"ve read about 7 inch is OK.
My couch would be about 17 feet away from the screen. is that ok ?

Sorry for all the questions, thanks for your help!!!!
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post #4 of 9 Old 11-03-10, 07:29 AM
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Re: How far should I put my projector

Quote:
Italbro wrote: View Post
Hi Mechman,

Thanks for the answer. Only thing is I am farely new to HT and not sure what you mean with 23fl to 9fl.
Would you suggest to put my projector closer ? If yes, how close.
Also, how many inch from the ceiling should my projector be ? I"ve read about 7 inch is OK.
My couch would be about 17 feet away from the screen. is that ok ?

Sorry for all the questions, thanks for your help!!!!
fL is foot lamberts which is a measure of luminance. The recommended fL for a home theater is 12-14fL. The closer you put your projector to the screen, the brighter the image will be. 15 feet from the screen will be fine for your projector.

As to how low/high to mount the projector, it depends upon the projector. Ideally you try to get it mounted at the same as the height of the top of the screen. But your Panny has 63% vertical lens shift so you've got a lot of leeway. Take a look at pages 15 & 16 of your manual.
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post #5 of 9 Old 11-03-10, 10:09 AM
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Re: How far should I put my projector

The FL will also depend on the gain of your screen material
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post #6 of 9 Old 11-03-10, 01:35 PM
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Re: How far should I put my projector

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The FL will also depend on the gain of your screen material
This is true because foot lambert (fL) is a measurement of screen LUMINANCE which is the amount of light reflected from a surface. The amount of light hitting a surface (like a projector beam) is called ILLUMINANCE which is measured in foot candles (fc). If the screen is a true white (reflects all the light that hits it) Lambertian (reflects the light in all directions from the surface) reflector the luminance and illuminance values will be the same. If the screen is a gray Lambertian surface (absorbs some of the light that hits it) the luminance will be less than the illuminance. Only when the screen surface has "gain" can a darker-than-white screen have the same, or greater, amount of luminance than the light illuminating it. When this is true the surface cannot be Lambertian, but must have some amount of specular or retroreflective reflectance. You can think of it as "robbing Peter to pay Paul" which means that while the reflectance on-axis with the PJ may be the same (or greater) than a white Lambertian surface the off-axis reflectance will be less than even what the gray screen would have had if it were Lambertian. We measure this screen attribute by taking multiple gain measurements from different angles.

A foot lambert represents the same amount of light as a foot candle, the only difference is the former is being reflected from the screen and the latter is striking the screen.

When we talk about screens and projectors we generally just use the term foot lambert for both luminance and illuminance even though that is technically incorrect.
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post #7 of 9 Old 11-03-10, 01:40 PM
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Re: How far should I put my projector

Don I love ya but you just gave me a headache.
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post #8 of 9 Old 11-03-10, 03:23 PM
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Re: How far should I put my projector

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Don I love ya but you just gave me a headache.
Wait until you read the article that's coming on the difference between a screen's "photometric gain" and "geometric gain".

You also see why we just use the term fL when we talk about screens.
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post #9 of 9 Old 11-03-10, 03:26 PM
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Re: How far should I put my projector

Please add "if your dumber then a 5th grader" clifnotes at the bottom of all future articles....
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