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Backlighting (D6500K)

Robert McJimpsey of Truline describes the need for backlighting below:

"Have you ever taken photograph's both outside in daylight and inside in incandescent lighting, and then found that in the pictures taken inside everything looked reddish ? If your answer is yes, then you know how adaptive your vision is to the color of white when the film is not.

What happens is your eyes loose their color reference. Again to have the correct reference for evaluating colors we need "daylight". This holds true not only when we evaluate the colors of a dress, but also when we evaluate the colors on a television. Also, watching television in a completely black room is straining on your eyes because the television is only occupying approximately 20% of your field of vision. This cause's the iris to open fully. Thus when a bright image comes onto the screen the iris is forced to close down quickly and sends the optic nerve into shock.

This is where the television surrounding come into play. Both the color reference and luminance level can be solved by mounting a light behind the set. The light supplies the reference that our eye's need. Clearly the choice of the light is not arbitrary, this light should be as close as possible to the D65 color standard. The lamp should be rated at 6500 Degrees Kelvin with as high a C.R.I. rating as possible. (Color Rendering Index refers to how well a light source will "render" an object familiar. The rating is scaled from 0 to 100 with outside "daylight" being 100) The lamp used should have a rating of at least 90 CRI."

Quick pointers from Guy Kuo

5 to 10% of the peak white intensity is recommended for the back light.

The AVIA DVD has a pattern which shows the correct luminance level. If your light matches that pattern in intensity, you're in range. Since the brightness of the pattern automatically goes up and down as you adjust contrast and black level, the pattern self corrects for the settings you are using.  I believe VE has a similar pattern, but only showing a single intensity rather than the top and bottom of the range.

Where to Get Them

If you search the web, you'll find a number of sources for the more popular brands (Chromalux & Lumichrome) of light bulbs/lamps used for full spectrum lighting.

Good Sources

  • M&M Lighting Co - source for both Chromalux & Lumichrome. Site lists Lumichrome 1XX in 18", 24", 36, & 48" lengths rated at 6500K with CRI of 98.   Minimum order of 6 lamps though.  May be a good idea for a group buy for this.
  • Kirkland Supply - yahoo search description says source for both brands although only the chromalux is listed at their site.
  • Home Depot, Lowes, or any local store might have D6500K lamps such as the Philips Daylight, F20T12/D
  • Sears - Westinghouse 18" 6500K 94CRI 15w T-8; about $10
  • Ace Store - Westinghouse F15T8/FS 18" 6500K 48CRI; about $15

Best Source

For THE place to get the lights specifically designed for home theater, you can only get them from CinemaQuest, Inc.

They are the only vendor that carry accurate 6500K, CRI 98 lamps.