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Discussion Starter · #1 ·
I have been reading about bias lighting for flat panel displays, usually in the form of an LED or rope light. I was wondering if bias lighting could help with my front projection setup and if so how would I implement it. I have a manual roll down screen mounted to the ceiling so light would only be visible on 3 sides of the screen. Currently the projector is in front a flat black wall, with decorative red drapes to the sides. I was thinking a 6500K light as dim as possible.

Opinions? Anyone have a setup with bias lighting? I would love to see some pics. Thanks.
 

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I think it would do more harm than good since it would add ambient light to the room - not a good idea for a projector setup.
 

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I had bias lighting behind my flat panel... really worked as advertised.

I took it down, though, when I installed my screen. Just because I didn't want to introduce any light into the room...

Sounds like a case where you'll need to experiment. I'm sure all kinds of factors (wall color?) would play a role in what effect it has.
 

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I have been reading about bias lighting for flat panel displays, usually in the form of an LED or rope light. I was wondering if bias lighting could help with my front projection setup and if so how would I implement it. I have a manual roll down screen mounted to the ceiling so light would only be visible on 3 sides of the screen. Currently the projector is in front a flat black wall, with decorative red drapes to the sides. I was thinking a 6500K light as dim as possible.

Opinions? Anyone have a setup with bias lighting? I would love to see some pics. Thanks.
Bias lighting is a technique that has been used by motion imaging experts and consumers for over a half century. The science and practice has been thoroughly defined, proven and documented for decades. If you want to understand what it is and why it can be beneficial in a given application, you only need to familiarize yourself with the fundamental principles that apply. Once you understand the fundamentals, the technique can be successfully implemented in a suitable application to achieve specific, desired, benefits. Here is a thread in this forum that sets forth the essentials: http://www.hometheatershack.com/for...508-fundamentals-d65-video-bias-lighting.html .

Bias lighting is used with direct-view type displays because of their elevated light output. Such displays are designed to compete with high ambient lighting and seldom operate correctly when lowered in light output to emulate front projection systems. TVs and monitors are generally recommended to be calibrated for 30 to 35 fL of peak white output in a predominantly dark room (SMPTE and other standards organizations recommend bias lighting be used in such a scenario). Commercial cinemas and residential front projection systems generally are recommended to be calibrated for 12 to 16 fL (total darkness is recommended as ideal for such systems). That's quite a difference in screen brightness for the human visual system to handle during extended viewing sessions.

If you were to attempt to implement bias lighting in a front projection system, all significant surfaces in the room that could reflect the lighting back onto the screen would need to be of a non-reflective nature or the integrity of the projected image would be compromised and contaminated. Since you will not see any commercial cinema screens or Motion Picture Academy screening room screens that use bias lighting, why are you wanting to do so?

Best regards and beautiful pictures,
Alan Brown, President
CinemaQuest, Inc.
A Lion AV Consultants affiliate

"Advancing the art and science of electronic imaging"
 

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I have always liked the way it looked on LCDs... I might have to try it on our front projection screen too.
 

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Discussion Starter · #9 ·
Bias lighting is a technique that has been used by motion imaging experts and consumers for over a half century. The science and practice has been thoroughly defined, proven and documented for decades. If you want to understand what it is and why it can be beneficial in a given application, you only need to familiarize yourself with the fundamental principles that apply. Once you understand the fundamentals, the technique can be successfully implemented in a suitable application to achieve specific, desired, benefits. Here is a thread in this forum that sets forth the essentials: http://www.hometheatershack.com/for...508-fundamentals-d65-video-bias-lighting.html .

Bias lighting is used with direct-view type displays because of their elevated light output. Such displays are designed to compete with high ambient lighting and seldom operate correctly when lowered in light output to emulate front projection systems. TVs and monitors are generally recommended to be calibrated for 30 to 35 fL of peak white output in a predominantly dark room (SMPTE and other standards organizations recommend bias lighting be used in such a scenario). Commercial cinemas and residential front projection systems generally are recommended to be calibrated for 12 to 16 fL (total darkness is recommended as ideal for such systems). That's quite a difference in screen brightness for the human visual system to handle during extended viewing sessions.

If you were to attempt to implement bias lighting in a front projection system, all significant surfaces in the room that could reflect the lighting back onto the screen would need to be of a non-reflective nature or the integrity of the projected image would be compromised and contaminated. Since you will not see any commercial cinema screens or Motion Picture Academy screening room screens that use bias lighting, why are you wanting to do so?

Best regards and beautiful pictures,
Alan Brown, President
CinemaQuest, Inc.
A Lion AV Consultants affiliate

"Advancing the art and science of electronic imaging"
Thanks for the info. I had suspected that bias-lighting would not be necessary for a setup like mine(front projection, light controlled, flat black everything except medium blue carpet.). I think for now I will give it a try on my bedroom LED which is almost exclusively used at night with the lights off.


Thanks to all that replied :T
 

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Thanks for the info. I had suspected that bias-lighting would not be necessary for a setup like mine(front projection, light controlled, flat black everything except medium blue carpet.). I think for now I will give it a try on my bedroom LED which is almost exclusively used at night with the lights off.
The only reasons I can come up with for implementing bias lighting in a front projection system are: the screen brightness is so high as to induce viewing fatigue or eye discomfort (very rare), or black levels are unsatisfactory and a perceptual improvement is intended by adding bias lighting (also rare with the newer projectors). If LED or incandescent rope lighting is used behind the screen, it is most likely not the right color temperature (even if the maker claims it is). I have tested several samples of LED rope light in recent years claiming to be 6500K. Not a single one has been lower than 8000K! Apparently, the Chinese think that any light that looks blue-white can be called 6500K. Such mislabeling is chronic in the so-called "white" LED market. The conventional incandescent rope lights are always yellow-ish, and become even more yellow/red when dimmed.

As soon as the wrong color of white illumination is used in a video display environment (either using the wrong light or the wall is not truly neutral), the viewer's perception of colors in the screen image will be distorted. Professional program mastering colorists are very sensitive to this issue when designing their work spaces. These are imaging fundamentals understood world wide by anyone with formal training in image quality. Unfortunately, the vast majority of consumers are oblivious to such factors. Even consumer electronics professionals are not well trained in the human perceptual factors important to designing good systems.

Some system designers and screen manufacturers are surrounding projection screens with color changing LEDs. This may have some aesthetic appeal in a room when the projector is not being used. However, using such lighting during a movie would only result in skewed color perception for the viewing audience. This scenario would be little different than requiring the audience to wear tinted glasses. What some novices might think is "cool" is actually counter-productive to making good pictures.
 
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