2014-10-13 CRI Rating on New Lights

LED bulb prices are still coming down, but the general public is still not aware of the advantages and still think the prices are too high. And the public is still unaware of the long term savings in electricity from which they’ll benefit. I still see 60 and 75 watt incandescents in dollar stores, which I thought were banned. And as I point out below, they have big benefits in color rendering.

I have noticed that the newer LED light bulbs have a CRI or Color Rendering Index rating on the bulb and/or the packaging.  I read somewhere that to qualify for federal rebates, a light bulb must have a CRI of 90 or more.  That gives the manufacturer an incentive to make a higher quality lamp.

I and some friends have been playing Rummikub at a house that has a dining room table under a ceiling fan-light ‘chandelier’. The “Large Numbers” Rummikub tiles are made of cream colored plastic with the numbers embossed on them. We have been having problems telling the difference between the blue numbers and the green numbers. They both looked very dull, like the colors were faded and turned muddy. One time, I pulled out my LED flashlight and illuminated some tiles in question and the colors were much brighter and easy to tell apart.

The three lamps in the fan light were 13 watt ‘corkscrew’ CFL lamps, of some brand I had never heard of. Since there were no packages, I couldn’t determine if these were 60 watt equivalents. The homeowner said that the electric company had replaced the old lights with new ones, and these CFLs were probably replacements.

I read online that the original incandescent lights emit a broad, even spectrum of light, even though the light is a low color temperature. This gives good color rendering across the visible spectrum, even though the red end gets more than the blue end of the spectrum. With the switch to CFL lights, the output is different. The incandescents use a white hot filament; the CFLs, as do any fluorescent light, use phosphors on the walls of the tube, excited to produce visible light by the ultraviolet light given off from the ionized mercury vapor in the tube. These phosphors give off a band of light, typically red, green and blue, with gaps of no light between the three colors. Any surface the light hits reflects back the colors, but if the surface is a color between the red, green or blue, then it reflects back less than it would if it were red, green or blue. Apparently the ‘blue’ Rummikub tiles are actually more of an aqua or cyan color, which is between green and blue. The CFL light makes it look more like a muddy blue-green, not much different than the green tiles.

I bought a 3 pack of 60 watt LED bulbs at Costco for $19.89, or $6.63 apiece (Costco brand?). I also bought a Cree 60 watt equivalent at Home Depot, on sale for $8.00, usually about ten dollars US. I intended to use the three pack in the fan-light, and I bought the Cree just because it was a good deal. Both packages said that the lamps had better color rendering. All of the lamps, including the old ones, were soft white.

I went over to the home and put two of the three LED lamps in the fan-light, and then we went to a neighbor’s and installed the other two in the swag lamp over her dining room table. They asked how much the LED lamps cost, and when I said $8.00, they remarked that that was too expensive. I thought that replacing two out of three lamps with LEDs would be enough to improve the light quality. In the end, I was right.

Last night we played a few games of Rummikub and every time we drew a blue or green tile, we both remarked how much brighter the colors were and how much easier it was to tell the difference. It was “like night and day,” to use an old cliché. Really, the difference was dramatic, even with just two of the three lamps replaced. Her daughter came home later with a bouquet of flowers, and the colors, especially the blues, were so much brighter, almost brilliant. Subtleties between the colors were so much easier to see. Now they are believers!
They think the LED lamp’s added expense is more than worth it. We haven’t yet played under the neighbor’s swag lamp yet, but I’m fairly confident that the results will be similar. I think they are going to want LED lights over their bathroom sinks, too, so that they will get better color rendering when they put their makeup on.

This real world example of poor and good color rendering has taught me how important it is. I hope to demonstrate its importance to others, especially to those who are responsible for displays to the public. The difference really is amazing.

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