I disagree with the LED lovers assertion that its a bias against them.. There's a lot to be desired in Ra8 system, which has been in use since early 20th century. This arbitrary scale has been engrained so deeply in the industry that its hard to change now.
There is no conversion factor between Ra8 and Ra14 (yet another arbitrary measure). It will have to be calculated from SPD and if high resolution SPD is not available for computation, the samples will have to go back to a lab for CRI measurement.
ounces are confusing as hell but we still use it.
A can of diet Pepsi is 12.5oz but can of normal Pepsi is 13.1oz by weight. but they're both "12 fl oz".
Even if it's straight water, "fl oz" and "oz" aren't the same. If they were, a gallon would weigh 8.0 lbs. But, a gallon is 8 1/3 lbs.
All of this non-sense will be cut if we use kg for weight and liters for volume. But it hasn't been done yet despite the fact we're in the 21st century. Unlike weight/volume measurements, there is no direct conversion, so it will be met by an even greater hurdle.
Look at RE80 fluorescent that is rated at Ra8: 86 and Chroma 50 rated at Ra8:90
Conventions will tell you the "4 points is negligible". However, there is a dramatic difference between the two lamps. RE80 is a very spiky polychromatic lamp that achieves high efficacy by tailoring the output to our visual sensitivities. Chroma 50 has much smoother spectral power distribution and much more optical power in the deep red region. Chroma 50 has a fair amount of R9 rendition. RE80s have R9 of zero which means materials that reflect only in the deep red region, such as fresh meat will look dull under triphosphor fluorescent lightning.
The "a" in Ra8 stands for "average" and 8 means 8 samples. Which is the computed result of renditions of each of eight color chips of arbitrary defined colors.
To visualize color distortion, we'll need engineering datasheet containing rendition data for each of the sample, get a high resolution SPD for a product, or send a lamp into a lab yourself.
Sales people typically won't have a slightest idea what you're talking about, so you will have to get in touch with someone at R&D. If you ask generic brands like Satco, you might get a response "WTF are you talking about? ".
Even R&D may not have retrievable rendition data for R9-14 or Ra14. They might be hesitant to release such data even if they did.
Osram Sylvania explains the value of R9 here:
http://assets.sylvania.com/assets/documents/FAQ0043-0605.15c933ce-e2d1-4896-92cf-7582ec74fc1e.pdf
The Philips 10W L-Prize winner bulb uses blue LEDs, red LEDs and blue to white conversion phosphor. I believe the red LEDs spike the long wavelength to improve R9 rendition. That lamp gets CRI 90 or something and LPW of 90 or so as well. But that thing costs $50/ea and it's not a representation of most LEDs.
If we manage to utilize Ra14, the labels will have to explicitly read Ra14 85, Ra8(legacy CRI) 90.. something along that line.
If LED sales people want to spend thousands of dollars sending their own and competitor products for independent testing, let them.
Thank you if you manage to read all the way to this line....
