Projection Distance - Home Theater Forum and Systems - HomeTheaterShack.com

Old 11-23-10, 09:22 PM Thread Starter
Shackster

Join Date: Sep 2010
Location: Kentucky
Posts: 48
Projection Distance

Hi everyone,

I have the Panasonic 4000U and need some HELP on understanding the projection distance and how that determines where you mount your projector for best picture.

Equipment List: (screen not purchased yet) - all other equipment has
Projector - PT-AE4000U
Screen - SMX 237.1 Curved (120 viewable width x 50.7 viewable height) = 130.2 diagonal - gain 1.16
Anamorphic lens - Optoma BX-AL133 with automatic sled - from what I understand, its basically a UH380.
Room - 15 wide x 22 length with no ambient light issues
Speakers inwall - L/R/C

Ok, the Panasonic manual states to use the following to figure the projection distance - diagonal screen size x 1.256 -0.04 = minimal projection distance and diagonal screen size x 1.899 - 0.05 = max projection distance.

So what I came up with is 130.2 diagonal screen x 1.256 -0.04 = 163.4912 inches or 13.6 ft minimal throwing distance and 130.2 diagonal screen x 1.899 - 0.05 = 247.1998 inches or 20.6 ft max throwing distance. Is this correct?

The Anamorphic lens documentation states that the throw distance divided by the image width (throw ratio) should be at least 1.6, prior to adding the Optoma BX-AL133 so, 16ft (192 inches) divided by screen width (120) would be 1.6 - Is this correct?

Going on the above information, If I place the projector at 16ft back, and using the projector calculator pro this would place me at 11fl, but from what I have heard, the lumen output on the Panasonic is no where near 1600 Lumens but rather like 500 Lumens and that would put me at a really low light level. Is this correct?

I am worried that the picture will be too dim projecting onto a 130.2 diagonal picture.

Any assistance is greatly appreciated. Thanks, Dean
DeanHT is offline

Old 11-24-10, 02:12 PM
Senior Shackster
Bob

Join Date: Jan 2010
Location: Idaho
Posts: 452
Re: Projection Distance

Dean,
I have my AE2000 at 16 feet from my screen (a DaLite 92 inch diagonal, high power, gain = 2.8) and the brightness in eco-mode knocks my socks off. The AE4000 is brighter still, although your screen gain is lower and your screen size will result in more light dropoff, so you might want to reconsider your screen material.
I found that the high power screen is great and with my room setup, directionality is not an issue. High power material has a very fine beading which makes it quite unobtrusive and preserves the sharpness of non-beaded surfaces. High power material, or equivalent, would more than double the brightness of your projected image (over what you listed as your screen gain) and might make your concerns moot.
RBTO is offline
Old 11-24-10, 07:22 PM
HTS Senior Moderator

Join Date: Oct 2006
Location: Murraylands South Aust
Posts: 8,317
My System
Re: Projection Distance

Quote:
DeanHT wrote: View Post
Hi everyone,

I have the Panasonic 4000U and need some HELP on understanding the projection distance and how that determines where you mount your projector for best picture.

Equipment List: (screen not purchased yet) - all other equipment has
Projector - PT-AE4000U
Screen - SMX 237.1 Curved (120 viewable width x 50.7 viewable height) = 130.2 diagonal - gain 1.16
Anamorphic lens - Optoma BX-AL133 with automatic sled - from what I understand, its basically a UH380.
Room - 15 wide x 22 length with no ambient light issues
Speakers inwall - L/R/C

Ok, the Panasonic manual states to use the following to figure the projection distance - diagonal screen size x 1.256 -0.04 = minimal projection distance and diagonal screen size x 1.899 - 0.05 = max projection distance.

So what I came up with is 130.2 diagonal screen x 1.256 -0.04 = 163.4912 inches or 13.6 ft minimal throwing distance and 130.2 diagonal screen x 1.899 - 0.05 = 247.1998 inches or 20.6 ft max throwing distance. Is this correct?
With an anamorphic projection set up, the projector should be placed back far enough that the image will fill the screen with the lens fitted and without any zoom applied..This would mean that by your calculations the projector needs to be positioned at the maximum distance of 20.6' to fill a 130" screen..

Quote:
The Anamorphic lens documentation states that the throw distance divided by the image width (throw ratio) should be at least 1.6, prior to adding the Optoma BX-AL133 so, 16ft (192 inches) divided by screen width (120) would be 1.6 - Is this correct?
The throw ratio is determined by dividing the 16:9 image width into the distance from the screen to the projector..You will need to know the width of the 16:9 image before you can calculate TR..

Quote:
Going on the above information, If I place the projector at 16ft back, and using the projector calculator pro this would place me at 11fl, but from what I have heard, the lumen output on the Panasonic is no where near 1600 Lumens but rather like 500 Lumens and that would put me at a really low light level. Is this correct?
The lower lumen figure represents a truer operational figure when the projector is used in low lamp mode..Although I would think it would be a little higher than 500 lumens..
Also all your pro calculator calculations should be done on the 16:9 AR.. not 2:37:1! I think you will find the your fL will increase significantly when you base all your calculations on the 16:9 image..

Prof..
Home Theatre...the never ending story!

www.dogboardingsa.com
Prof. is offline
Old 11-24-10, 09:27 PM Thread Starter
Shackster

Join Date: Sep 2010
Location: Kentucky
Posts: 48
Re: Projection Distance

In the manual it advises when projecting both 2.35:1 and 16:9 images onto a 235.1 screen using the lens memory function with a 130" diagonal image the projection distance is 13.7 minimal and 20ft maximum. Does using the anamorphic lens change this distance that much that it must be at the max distance?

Last edited by DeanHT; 11-24-10 at 09:51 PM.
DeanHT is offline
Old 11-25-10, 04:42 PM
HTS Senior Moderator

Join Date: Oct 2006
Location: Murraylands South Aust
Posts: 8,317
My System
Re: Projection Distance

Quote:
DeanHT wrote: View Post
In the manual it advises when projecting both 2.35:1 and 16:9 images onto a 235.1 screen using the lens memory function with a 130" diagonal image the projection distance is 13.7 minimal and 20ft maximum. Does using the anamorphic lens change this distance that much that it must be at the max distance?
The lens memory function of the projector and projecting through a lens are two totally different things...
With the lens in place you leave the projector in it's native mode !6:9 for 2.35 movies..and so everything is set up using that AR..

With a 120" wide screen your !6:9 image is going to be approx. 84" wide..
Looking at the pro calculator, an 84" wide image with no zoom applied puts the projector back about 19'! That gives less than adequate lumen output..That projector has a very long throw lens..

One way to improve the lumen output would be to apply some zoom..This will bring the projector in closer and raise your lumens..Doing this will reduce your TR a little and may add slightly to the pincushion effect, but you should still be ok..

Prof..
Home Theatre...the never ending story!

www.dogboardingsa.com
Prof. is offline

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