Projector mounting question

[lugano]

Hello folks, regarding the ceiling mounting of my new Panny projector I have a very simple question. Thanks to the zooming I am quite flexible at where to place it, in terms of distance from the screen. My logic says: the nearest possible to the screen will maximize perceived brightness. Am I right ?

 

[Tj Bassi]

Back in the days before projectors had the nifty zoom feature, the mounting location was determined by figuring the throw distance for a certain screen size (usually width as opposed to diagonal measurement), which usually gave you a mount location +/- a few inches, depending on your particular projectors focus range. In this case, it is the ultimate size of the screen that determines image brightness, not the throw distance.
Remember, that your projectors bulb is the ONLY source of light for the image, and within the constraints of a typical home venue, the projector mounting distance doesnt really affect image brightness as much as other factors, such as screen material choice, ambient lighting, etc.
When I mount a newer projector that has is flexible in placement, I tend to keep it more towards the farthest of allowable throw distances, for two reasons. The first is noise.....some projectors are somewhat noisy and having this noise overhead or in front of a viewer is distracting (some newer projectors also run quite hot). The second reason is that the farther from the screen you place the projector, the less of a projection angle you have to offset (image keystone). If your projector is ceiling mounted (or floor) and fairly close to the screen, the image will skewed and you will have to correct this. Some projectors do the correcting in the optical train but others handle it in the digital realm and extreme keystone angles can induce image artifacts you would have to live with. Last thing to consider is your projectors mounted height......for a particular throw distance, some projectors have to be within a certain vertical measurement of screen center (measured vertically from the ceiling.) You dont want to wind up in a situation where in a room with an 8 foot ceiling, your projector has a vertical drop of more than a few inches.
Personally, I'd take the median throw distance and see if that works in your viewing room. That way, you would have an easy image setup, and future flexibility in case you move your screen or seating.
But to answer your basic question....No, a closer mounting position wont maximize your perceived brightness. In a very large venue it could be a factor but in the average home viewing environment it would be unmeasureable.

Tj

 

[JonFo]

+1 one on TJ's feedback. Well put.

When I had a digital (and I'm considering augmenting the CRT with another digital), I run them at their max throw to move them behind the viewers.

 

[Audiophiliac]

I usually mount them wherever is most convenient given the room layout. I do try not to place it at one extreme or the other...the focus range can be a bit hairy at the ends of its adjustment.

The other KEY factor is height. A lot of newer projectors have lens shift. SO you can mount the lens higher or lower than the screen and move the image up, down, left, right, without having to keystone. KEYSTONE IS BAD!!! Expecially in digital projectors. DO NOT KEYSTONE! That is like the first rule in digital projector setup....get the height right. Most often, the lens center needs to be within the screen height. I always try to align the lens center with the top edge of the screen. Make sure it is exactly in the horizontal center, and everything is level and you should be good to go.

 

[Tj Bassi]

Should have made note of that in my first post. Most newer projectors assume a mounting position approx even with screen top and centered, projector level. Lens shift is a feature that greatly simplified projector setup and contributes to an overall better image than one corrected from an off-axis projector mounting.

T-

 

[lugano]

But to answer your basic question....No, a closer mounting position wont maximize your perceived brightness. In a very large venue it could be a factor but in the average home viewing environment it would be unmeasureable.

Tj

Thanks a lot for your input. Somehow I thought that having the pj 2 meters nearer to the screen would have been a good idea. I will experiment on monday/tuesday, when it arrives, then decide. No problem to walk around with it, adjusting zoom and focus - this time I want to get it right, right from the start.

 

[Tj Bassi]

At quick glance it seems like a good idea based on common sense, but it's not something that translates to a real benefit in the actual application. Your projector puts out a certain amount of light (which is all generated by the lamp) and as long as you are within the throw distance/min max zoom of your unit, and are completely filling the screen with the image (and not overly masking any of the borders), moving the pj two meters closer should have no visual impact on the image brightness, and probably no benefit that could be measured even with good equipment. Sure, you could do a test and walk the projector right up to the screen, and it would appear to be quite bright, but all you have done is created a hot spot with little chance of that image being acceptable to anyone watching it.
As long as you have made a good screen choice (and the subject of choosing a screen could take pages to discuss....) and can properly control ambient light in your room, I think you'll find that your new projector has more than enough light output to throw a great image. Most DLP/LCD/LCOS units do well at projecting a 'bright' image and many even have an optional lower-power lamp mode which may still be satisfactory. If anything I feel that there is little or nothing to be gained by moving closer to the screen and much to be gained by controlling the lighting environment. Most digital projectors I've worked with put out a pretty good picture even at moderate contrast levels.


T-

 

[kcl]

The 'luminance' output output by a projector is measured in Lumens and is relatively unaffected by the distance between the projector and the screen. What you're referring as 'brightness' is measured by Foot Lamberts, which is the light output in Lumens divided by the square footage of the display screen. The reason you experience brighter displays when you move closer is simply because the display area decreases, raising the foot lamberts.