D65 backlighting for TV displays

[Reid Malenfant]

I'm not sure how many people have heard about or actually use this so i figured i'd get a post up about it

D65 back or bias lighting actually improves the picture that you'll see on your TV & help prevent eye strain. The proof of the pudding is in the eating so they say. As i own a Philips TV with Ambilight i can have lots of pretty colours blown on to the wall behind the TV that is supposed (according to Philips) to enhance the viewing experience. These are or can be set to match colours that are produced around the screen edges. What it actually does is distort the colour that you view on the screen. I'll see if i can find something to demostrate this, i think you'll be pretty surprised, i know i was

Having discovered this & being lucky that i happen to have Ambilight spectra 3 i soon discovered that i could set the Ambilight to very close to the colour temperature 6500 Kelvin (6500K - D65) & lock it there. The difference this made to viewing was pretty astounding to say the least. No light need to be on in the room as the Ambilight supplies enough from behind the screen to do whatever you need to do. It also improves the contrast ratio

All that is needed to carry this out is some kind of 6500K source of light with a colour rendering index (CRI) of 90 or more. Something like a 15W triphosphor 6500K energy saver right hard up against the back of the TV itself should do the trick for a 42" TV Other tubes that could be used include older halophosphate tubes such as "Northlight" at about 20W due to it being less efficient.

What you are aiming for is about 10% of full screen white brightness as a maximum Smaller TVs will need less powerful tubes, larger TVs a bit more..

Here is a bit of bumph i just found just so you don't think Mark has lost the plot

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, such as 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 many optical disc programs for setting up home entertainment systems (see: 'Avia II- Guide to Home Theater,' 'Digital Video Essentials' series, etc.).

What are the proven benefits of correctly implemented 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 by enabling dark room viewing and lowering of screen brightness requirements (phosphors are used in CRTs, plasmas, and LCDs with CCF or white LED back lighting).
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



Courtesy of this site here

[sburrell]

Funnily enough I read something about this recently when reading up on how to calibrate my TV. As a result I now use an Ikea lamp behind my TV at night as my sole source of light. I don't think it's the correct colour temperature or anything, but it's a nice start.

Something you didn't mention was that cinema auditoriums implement side-lighting using this principal - the auditorium is never allowed to be lit solely by the movie. This convinced me to give it a try.

I hope others give this thread a read, because I find it makes a very pleasant difference to my viewing experience, and I've not even implemented this according to the defined specs.

It actually makes me think I should do the same for my computer monitor - I often play games into the night in an otherwise unlit room, and can vouch for the sensation of eyestrain. Hmm, may go out today and try to source the right equipment...

[HighFidelityGuy]

Hmm, sounds interesting. Could this be done with LED's to make a low power consumption version?

EDIT: Scrap that, a quick eBay search tells me you can....

[sburrell]

I've just been phoning around, and found this for under £4:
http://www.amazon.co.uk/PureLite-Nat.../dp/B004GAXCQY
On another website it was described as a 6500K bulb, though I can't find a manufacturer's website to confirm.

[HighFidelityGuy]

Here's an LED one that states 6500K: http://www.energybulbs.co.uk/product...ght/2876887848

[sburrell]

I just picked up one of these in John Lewis for £2.10 - 11W (50W), 590lumens, 6500K, along with a suitable wee lamp. I got the lowest lumen emitting bulb I could find, to try to aim for the 10% total screen brightness value you referred to (I calibrated my display to 100cd/m^2, so knowing the size of the screen I imagine I could actually calculate the exact values I need, right?)

I had a chance to test the bulb whilst in the store and I was astonished at how blue it appeared against the rest of the store lighting - I calibrated my own monitors to 6500K and don't recall them being that blue, but then perhaps it was the contrast with the store lighting that emphasised it?

Anyway, I'll be testing this out this evening when I get in, replacing what must be a rather warm bulb in the Ikea lamp for this one - should be interesting!

I was reminded of something a step-uncle showed to me once. He was a sufferer of S.A.D. and had a light box for that reason, and he demonstrated the effect it had on colours when viewing the art on the walls of his living room - more were visible, especially in the purples.

Whilst I realise that most TVs are back-lit, I suppose there's an element of reflection to, so ambient light temperature must have some bearing on the viewing experience.

Anyway, I'll report back with impressions later.

[HighFidelityGuy]

I remembered I had a couple of LED GU10 bulbs spare that I found to be too blue/white for use as a normal room light. So I stuck them in some spare up-lighters and mounted them behind my TV pointing at the wall.

Here's what it looks like:

With one light:



With two lights:



They both look a bit brighter in the photo's than in real life and the ring shape is less prominent too. No other lights were on in the room. I can't decide whether one or two bulbs look best yet but I think two. What do you guys think?

[HighFidelityGuy]

Here's the temporary setup behind my TV:

[sburrell]

Well, I guess it depends what you find better on the eye. I'm cognisant that Mark specified a 10% of total screen brightness for the ambient lighting - that's pretty low, according to my colorimeter. I'd go with the single bulb for that reason.

I set up mine and found the 50W output of the 11W bulb too much, so I've covered the top of the shade with a speaker grille from my Monitor Audios, and it's much better.



I like it. I think it _is_ easier on the eyes. I'm going to live with it a see how things go I'll have to find a better way of mounting the lamp round the back though - the box it's on just now reflects too much light. I'll try to find some material (perhaps felt) to cover the box tomorrow.

[sburrell]

I removed the magnolia carpeting from the fireplace and replaced it with some beige upholstery fabric, and I think it looks a lot better. The magnolia was too reflective and, well, the cats had been at it so it was getting tatty. Here's how it looks now:

Neater and less reflective, and the colour strikes me as being more auditorium-like.

Oh, and yes, that is Van Damme - his nipples talk to him when it gets cold. Probably one of the few ad campaigns that actually makes me want to buy the related product!