cinemaquest Ideal-lume

ideally you want a neutral color to the wall behind/near/around the display like light grays or whites... but bias lighting has many other benefits that can be achieved even if the surrounding walls are not perfectly neutral

"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."
Edited by PlasmaPZ80U - 2/11/13 at 8:24pm

Any technically neutral wall color from a medium/dark gray up to white will work for a video display surround. The lighter shades will help with black level and contrast perception when viewing the TV while the room is fully lit. Just the wall behind the TV is the minimum recommendation for neutral color. The principle at play here is the fact that any conflicting color within the observer's field of view, while watching the screen, will distort color perception. More vivid or saturated colors will have greater effect, less colorful surrounding surfaces will have lesser effect. The only way to insure the viewer will perceive the colors correctly in an image is to provide a neutral surround, with ambient lighting as near to the D65 white point of video as possible.

A colored surround actually subtracts the same color from what our eyes observe in the screen image. This perceptual phenomenon occurs in the brain and is inescapable, although subtle in cases like yours with a light pastel wall color. A marvelous graphical demonstration of this phenomenon can be experienced at this link: http://www.echalk.co.uk/amusements/OpticalIllusions/illusions.htm . Go down to the fifth section of illusions, titled: 'Colour perception.' Use the slider included with each demonstration to adjust the mask opacity of the color surrounds. You will see that even very slight coloration in the surround affects the perceived color of the object of focus.

When the Society of Motion Picture and Television Engineers (SMPTE) published their seminal work on best practices for designing video viewing environments, very little discussion dealt with viewer comfort (SMPTE RP166-1995). The dominant focus in the document dealt with preserving correct color perception. This focus may simply be by reason of the paper's subject dealing with color video, rather than monochrome video. Nevertheless, this area of the forum discusses display calibration. It's a simple scientific reality that a "perfectly" calibrated video display cannot be perceived as having accurate color if there is a conflicting colored surround within the observer's field of view. A spectral analysis instrument cannot measure what occurs in the visual cortex of the brain. Therefore, the simplest way to ensure image fidelity is to provide a calibrated display and a neutral surround in the viewing environment.

A single Ideal-Lume Standard should provide more than enough illumination for your size of TV and your light colored wall. We have had users report to us that the single light was sufficient for their 73" RPTV and a white wall. You're certainly welcomed to call our office regarding questions of this kind. Unlike most consumer electronics manufacturers, we are a tiny company that responds to customer inquiries well. In most cases you will likely end up speaking directly to me.

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

"Advancing the art and science of electronic imaging"
Edited by GeorgeAB - 2/21/13 at 10:28am

To hijack this thread a little bit, is it possible to measure the light behind the tv using a spectro (xrite 2), and should it then measure the same white as is needed in tv calibration?

There are meters that could measure the illuminated surround area, but they would tend to have a fairly small angle of view and be able to read reflected light (from the wall) as well as directly generated like (from the TV panel) in order to successfully measure the lighted surround area. I don't know the properties of the particular meter you asked about... but if it has a large angle of view, I don't think it would work unless it was VERY close to the wall you are trying to measure which could create a shadow problem depending on how things are organized... and if that meter cannot be used as a reflectance meter (you need a reflectance meter when measuring images from projection screens, for example), then you'd also be out of luck.

But the general answer is yes, you would want the illuminated surface around the TV to measure as close to the d65 standard as possible. If the paint is neutral gray and the light source is very close to d65, you'll measure something close to d65. If the wall is yellow and the light source is blue, you might eventually be able to tweak the paint color over many attempts to get a d65 result from wall and light colors that would be terrible choices by themselves... but what's the point really? Just use neutral gray paint and a known d65 light source.

If you have a big enough deviation from D65 coming from the wall, then you might be able to find a suitable theatrical gel to get things closer to target.

My tube measured well (i1 Display Pro), but the wall was overly red and it was very obvious to my eye. I calculated that a CT 1/8 Blue gel would be the best commercially available filter that could tame the red but still allow sufficient light output (and this part is important because dimming the light too much defeats one of bias lighting's most important functions).
Very happy with the result and I cannot tell that there is any obvious error without instrumentation.