Quote removed - Norm
No need to be so hostile, SemiMan... even if you are right about the CRI. I'm not sure about the warm/cool LED's though.
CRI is a definition. It only relates lights under 5K to a blackbody radiator and lights over that to the sun. It does not indicate the ability to render colors well across all color temperatures though. It is very difficult to see the "richness" of a blue/blue-green object under 2700K incandescent even though that light source is 100CRI. That said, depending on what you are looking at, you will notice the difference between a good 85CRI LED bulb at 3000K and a 100CRI halogen at 3000K. If either was just turned on in a room though, 95%+ of people would not think anything was wrong with the LED bulb and would just assume it was a halogen incandescent. Yes that has been tested. If a comparative test was done and people were told what to look for, then yes some (not all) would be able to tell the difference.
As you get to cooler temperatures of almost any light source, the relatively shift in intensities to more blue / blue-green, means that things that are being lit that are those colors become brighter with great color contrast. Those particular objects will become more "pleasant" to look at. Unfortunately, with many cool white LEDs that also comes with elimination as opposed to the reduction of deep reds (and the addition of some spectral holes). So now while blue and blue-green objects look pleasant, red and yellow objects look "unnatural" and washed out.
There are however very high CRI sources in both the 3,000 and 4,000K ranges, but unfortunately not really at higher color temperatures. Some of these are made with the use of multiple phosphors which gives an almost blackbody response. They achieve high CRI both in the saturated colors of R8 CRI, as well as the pastels of the extended CRI color set. Unfortunately, these tend to give up a lot of efficiency as to achieve that blackbody response, they also create light outside the visible range which is wasted and even in parts of the visible range where our luminous efficiency is low. Other high CRI sources, typically at low color temperatures, mix a particular cooler white LED with red LEDs. This fills in the missing red, but without the loss of efficiency of phosphors that have output outside the visible range and in low response ranges of the visible range. This particular measure can still achieve high CRI with the saturated colors and pretty good CRI across most of the extended CRI color set. This is how Cree can achieve 100+ lumens/watt at the fixture level with warm white.
There is work being done on other color measurement systems including CQS (color quality system) that seek to solve the deficiencies of the CRI system, one of which is that color differences are treated the same for all colors and two that currently only the smaller color set of saturated colors is used for CRI. Unfortunately, like any standard, getting a bunch of experts to agree on the same thing is like herding monkeys. It is not easy.
Semiman