Visually measuring CRI

[Garth Herrick]

Holly,

Thanks for your thorough and enlightening report on the Lumichrome fluorescent lamps. You have given me the courage to share my own light tests for comparison.

I am including a similar shot of my new Just Normlicht Color Control daylight 5000 fluorescent lamps, and for comparison the earlier Phillips lamps I had installed before. I was not able to get as far away from the lamps with my camera as you. My camera was about eight feet away, and the diffusion screen was about two feet closer. For the Just Normlicht shot, I had only one lamp lit, while for the Phillips shot, two were lit, which is obvious in the image. I too am surprised that the digital camera can only see the red, green and blue light in the spectrum. To my eye there was much more. What the camera cannot see are the deep intense blue-purples, the brilliant turquoise, the yellow range, and the deepest garnet reds.

Despite the shortcomings of my photography, the Just Normlicht T-8 5000 K lamp seems roughly comparable in its CRI index to the Lumichrome T-8 lamps in your test. The salesman claimed the Just Normlicht has a CRI of 98. Compared to the Lumichrome 5000 K lamp, it appears to be at least as good, as it looks to have the smoother spectrum graduations like the Lumichrome 6500K lamp.

Again thanks,

Garth