# The Fundamentals Of D65 Video Bias Lighting



## Alan Brown

*
Introduction:*

This post is intended to simplify, clarify, and serve as an easy educational reference for, the technique of bias lighting for TVs and monitors. It is product agnostic and makes no direct reference to any specific commercial lighting solution. The technique of video bias lighting has been in use for decades by professionals and consumers who understand what is required for optimum picture quality and viewing comfort when using electronic displays.

Video programs are mastered on calibrated professional monitors in "dim surround" conditions. It has long been understood that the best viewing condition for television programs is in a darkened environment. Total darkness is not recommended due to the limitations of the human visual system. Televisions and similar electronic displays are much brighter than large format front projection movie screens, which don't require supplemental illumination in the room.

*What are the recommended elements of properly implemented bias lighting?*

1. The color of light should be as close as possible to the video white point of 'CIE D65' (loosely referred to as 6500 Kelvins) for color video viewing ['D50,' the 'E' point, or ~5400K in other specific applications].
2. The color rendering index (CRI) is often published for a given lamp. A minimum CRI of 90 out of 100 is recommended for color reference applications.
3. The illumination should originate from behind the frontal plane of the screen to avoid reflections, haze, and glare (which interfere with, contaminate, and obscure the image).
4. The lamp itself should not be directly visible to the viewer, but rather the illumination should be reflected by surrounding surfaces or the wall behind the monitor.
5. The brightness of the reflected illumination should be 10% or less of the brightest white the monitor is adjusted to (calibrated for a dark environment).
6. Surrounding surfaces within the observer's field of view of the monitor screen should be neutral in color (gray to white), see: Munsell Color Order System's neutral value scale.
7. Completely surrounding the monitor screen with illumination is not necessary to realize the principle benefits of the technique.
8. It usually works best for the lamp to be mounted on the back of the monitor or TV cabinet (rather than on the wall), in order for the illumination to spread out over some distance.
9. Test patterns for adjusting bias lighting relative to the monitor screen are available in most optical disc programs for setting up home entertainment systems (see: 'Avia II- Guide to Home Theater,' 'Digital Video Essentials,' etc.).

*What are the proven benefits of bias lighting?*

1. Reduces or eliminates eye strain and viewing fatigue in dark viewing conditions.
2. Eliminates image contamination due to reflections, haze and glare on the screen from conventional room lighting.
3. Enhances perceived black levels, contrast ratio, and picture detail by enabling dark adapted viewing.
4. Preserves correct color perception of the video image by the viewer.
5. Prolongs monitor phosphor life (phosphors are used in CRTs, plasmas, LCDs with CCF or white LED back lighting) by enabling dark room viewing and lowering of screen brightness requirements.
6. Provides a low level of illumination in the room for movement and peripheral activities.

*Says who?*

The following organizations are confirmed to define, recommend, specify, and/or use the technique of video bias lighting:

The Society of Motion Picture and Television Engineers (SMPTE)
The International Organization for Standardization (ISO)
The International Telecommunications Union (ITU)
The National Institute of Standards and Technology (NIST)
The Metropolitan Museum of Art
Industrial Light and Magic (ILM)
The Imaging Science Foundation (ISF)
THX, Ltd.
Electronic Arts (EA)
by deluxe
Microsoft Corporation
Image Entertainment
Universal Studios
PostWorks
Joe Kane Productions
Ovation Multimedia
DisplayMate Technologies
CNET Labs
Radical Games
Factor5 Studios
High Moon Studios
CinRam
Rev13 Films
Advanced Television Evaluation Lab- Communications Research Centre- Canada
Apple Corporation
Filet Post Production
Post and Beam
Cheyenne Mtn. Entertainment
Zombie Studios
CBS Television
Deluxe Digital Studios
Splice Here
Slant Six Games
New Hat LLC
Roush Media
Samsung Germany
Digital Film Lab- Denmark
Nice Shoes, VFX New York
Desperate Housewives, Editorial
Rockhopper Post
Live Nation Studios
LionAV Consultants
Avical
Technicolor-NY
Technicolor-Canada
Max Post
Bandito Brothers Studio
Chainsaw Edit
Twin Cities Public Television
Colorflow Post
ABC Television
The Moving Picture Company
*
Technical references for more detailed explanations of bias lighting:*

SMPTE Recommended Practices document: RP166-1995: _‘Critical Viewing Conditions For Evaluation Of Color Television Pictures’_
ITU-R BT.710-4 _'Subjective Assessment Methods For Image Quality In High-Definition Television'_
ISO 17121:2000: _'Cinematography -- Work stations used for film and video production -- Requirements for visual and audio conditions'_
_'The Importance of Viewing Environment Conditions in a Reference Display System'_ G. Alan Brown, http://www.cinemaquestinc.com/ive.htm
_'Digital Video Essentials: HD Basics'_ Blu-ray Disc program, by Joe Kane Productions
_'Tips on Buying a New Flat Panel Display'_ NIST Flat Panel Display Laboratory, http://www.fpdl.nist.gov/Tips.pdf [includes graphic demonstrations of screen reflection issues]

*Pertinent technical quotes:*

_*"Monitor white reference: In additive mixture, the illumination of the reproduced image is generated entirely by the display device. In particular, reproduced white is determined by the characteristics of the display, and is not dependent on the environment in which the display is viewed. In a completely dark viewing environment, such as a cinema theater, this is desirable; a wide range of chromaticities is accepted as “white.” However, in an environment where the viewer’s field of view encompasses objects other than the display, the viewer’s notion of “white” is likely to be influenced or even dominated by what he or she perceives as “white” in the ambient. To avoid subjective mismatches, the chromaticity of white reproduced by the display and the chromaticity of white in the ambient should be reasonably close."*_ from Charles A. Poynton, _'Digital Video and HDTV Algorithms and Interfaces'_

Also here: http://www.hometheatershack.com/for...ors/28480-viewing-environment.html#post260250

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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## event horizon

Hi Alan, i just want to say what a great post that is :T

When using my old Toshiba 42Z3030 i always had a 16W energy saver in a lampshade slightly to the side but behind the front of the screen. It was the wrong colour temperature though at about 2700K, not 5000 or ideally 6500K.

However, i think the latest TV has cracked it as it's a Philips with "Ambilight". This throws out the same kind of colours that are being produced on the screen & in different areas near the side & top edges (nothing from the bottom edge). The effect is rather interesting to say the least. No need for the lamp any more 


By the way, cheers for the recommendation of Spears & Munsil Benchmark blu ray. In combination with the DVE HD Basics blu ray & calibrated TV i now have a picture that i never imagined was possible! Thank you :thankyou:

Regards, Mark.


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## Alan Brown

Mark,

I'm glad you found value in my contribution. It's not clear to me what is meant by, "cracked it." The 'Ambilight' feature set used to offer a constant white mode that could be dimmed to the proper level for serious viewing. However, reports from calibrators found that the color of white was not very close to 6500K or D65. The multi-color modes are strictly a novelty and actually distort color perception for the viewer. Here is a forum thread that explains why and how the principles work in the human visual system.


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## event horizon

Hi again Alan, well i'm not 100% sure which Ambilight system you are refering to. Very interesting link & further links by the way :clap:

What this TV has is Ambilight 3 which admittedly does make a load of fancy colours if set that way. It also has a plain so called "white" setting which i guess was what you were refeing to, but it also has a "custom" setting. As i have no experience of earlier Ambilight systems i'm not at all sure if a custom setting was available. This will allow me to adjust the colour balance & lock it.

If it wasn't then at least i stand a decent chance of getting closer to D65. This looks to me to refer to the same colour output of a few old type fluorescent tubes, Northlight which was 6500K & represented the colour given off by the scattering of light at noon in the northern hemisphere & what is now refered to as Daylight or 6500K or there abouts. As i happen to have a few 6500K fluorescents knocking about i'll have to see how close the Ambilight can be adjusted.

Thanks again for your input


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## Alan Brown

It sounds like the 'Custom' option may indeed get you close to the D65 video white point. You would need a color analyzer to know for sure. You could have a professional calibrate the TV and the 'Ambilight' mode in one visit. Please explain what "cracked it" means.:help:


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## event horizon

Alan Brown said:


> Please explain what "cracked it" means.:help:


Sorry Alan. In this instance it'd mean something like this:- No need to install D65 bias lighting as the TV does it itself (if i can get custom close enough).

Or if you like, "the jobs a good one" or "done & dusted".

I apologise for being English & occasionally difficult to understand 



> You would need a color analyzer to know for sure.


Would a spectroscope be good enough for that?  If so then again, the jobs a good one 

If not ah well


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## Alan Brown

No need to apologize. I assumed it was UK slang. Any color analysis instrument that reads the whole spectrum, rather than just a tri-stimulus probe limited to red/green/blue, should work. The white point for video D65 has chromaticity coordinates of CIE x-0.3127 and y-0.3291. A target tolerance of +/- 0.005 is pretty good for this application.


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## Alan Brown

Here are a couple of pertinent excerpts from Charles Poynton's 5/26/10 article titled:'B, V and M Are Obsolete'

"I use the word “reference” because the display used at the end of the
content creation chain establishes the intended reference for all downstream
displays. If an identical display is present downstream *in an
identical environment*, then it should present an identical picture. In
the consumers’ premises, we don’t expect the tight tolerances of
a studio display, but *we do seek the same aim points*."

"*Color appearance is strongly influenced by surround conditions*. My
recent proposal for a new standard is entitled 'studio HD reference
display *and viewing conditions*.'" [emphasis is mine]

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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## Michael Osadciw

Alan

Great thread to bring to Home Theater Shack. All should read! I will also second the need and importance of video bias lighting. Many of my clients have attached them behind their panels to match the target white point of the monitor: D65.


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## Andre

I tried this in my HT and found it distracting, ended up going back to the dark room. Weirdly enough I put in some black lights in the two sconces in the front of the HT on the side walls and found with them on (dimmed halfway) the room felt more comfortable.


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## Dave Upton

I built one of these using a D65 lamp a while back to use with our plasma, since moving to a PJ I haven't seen a need anymore but it sure did help with TV watching.


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