Originally Posted by Elisha
But Richard, cinema 6.5k is different than lighting 6.5k. If you look at HID 6.5k bulbs, they are bluish. Ice blue in fact. OEM bulbs are normally 4,300 to about 5,000k and they are closer to the cinema white on screen.
So when the LED guys say 6,500k, they are most likely not basing it on cinema 6.5k.
Originally Posted by Rolls-Royce
A lot of people confuse D65, which is a specific point on the CIE chart, with 6500K, which can range from a cyan to a magenta tint. It can range this way because from what I've read, blue is not taken into account when computing a Kelvin value. It's likely the reason for the range in 6500K observations from HID bulbs to "cinema 6.5K" (which should be D65).
True, 6500K (Kelvin) is not the same as D65. The color you get from a 6500K light source can vary due to the shift of magenta/green, whereas D65 is an exact, non ambiguous color. As
said above, "D65 is a specific point on the CIE chart".
However, that said, the Color Temperature of "The MediaLight 6500K Bias Lighting System" (www.biaslighting.com
) is actually very close to D65.
In fact, the original name for them was "MediaLight D65". NOTE: No Bias Lights out there will be precisely D65.
It was Bram Desmet, General Manager of Flanders Scientific Inc
(a supplier of high quality professional equipment to the broadcast and post production industries, who sell a lot of these Bias Lights to professional colorists) who advised them that they should think of changing the name because some of his professional customers could say the lights were not precisely D65. The tolerances with professional monitors is much lower than with consumer products.
"He said that he would buy a ton of them if we didn't call it MediaLight D65. So we renamed it MediaLight 6500K."
As I stated above, the MediaLight bias lights are, according to Jason, very close to D65. They were actually measured with a 2nm spectroradiometer (borrowed from Flanders Scientific Inc
). "Joe Kane uses a lowly 5nm. You know, a cheap piece of garbage for $10,000".
NOTE: I know all this from a private conversation I had with Jason Rosenfeld, Director of Scenic Labs Inc
Experts agree that a bias light should be the colour of sunlight on a hazy day, or something called the CIE D65 standard illuminant. We used a calibrated Photo Research SpectraScan PR
-650 to measure our component light emitting diodes. Our partners then tested them on their PR
-670 to verify our findings.
Our lights are not only accurate enough for home use, they are used by professionals who colour grade the videos we enjoy on our home theatre systems.
We don't believe that any of the bias lights on the market, including our own, should be marketed as D65. The CIE D65 standard illuminant is derived from sunlight in a slightly hazy sky. In our view, any artificial bias light is "simulated D65," and has different spectral power distribution than natural sunlight.
So, yes. To the extent that an LED is capable of simulating the CIE D65 standard illuminant, The MediaLight is a very accurate solution.
Video experts have found that using the right color of white light behind the TV helps preserve correct color perception of the picture. According to TV professionals, TV pictures look more natural when the light in the room is in the same color temperature as the CIE D65 industry reference standard.
The CRI (Color Rendering Index) of most types of lamps is referenced to the spectral content of a standard element heated to a certain temperature on the Kelvin scale. Illuminants rated at 5000 Kelvins and higher are referenced to natural daylight at varying times of day.
Our video monitor luminaires are rated at 6500 Kelvins
. This color of white light is the same as that displayed on a correctly calibrated TV set. Using 6500K ambient lighting in a video viewing environment preserves accurate color perception of images on the screen.
Industry experts [also] recommend a CRI of 90 or better in applications where color recognition is a priority.
Hope this clarifies things.
Just one final NOTE:
The SMPTE ideal recommends that the wall behind the set be a neutral color to further preserve correct color perception. Colors classified as neutral by the Munsell Color Order System
, range from white to black throughout the gray scale. Vivid colors should be avoided if they are used within the field of view of the TV screen.
The SMPTE Recommended Practice
document says the brightness of a bias light as reflected off the surface behind the TV should be less than 10% of the peak white level on the viewing device.