Deciphering the Color Rendering Index [CRI]Or, Why CFLs Still Don't Look All That Good

Deciphering the Color Rendering Index [CRI]Or, Why CFLs Still Don't Look All That Good

Jonathan B.
Apr 14, 2008

So you've been good: you used our advice to switch nearly all your bulbs to compact fluorescents. You made sure to get the right color temperature and buy bulbs that come up to full brightness quickly. Your energy bills are down, but somehow your interior has lost a bit of zing. Is it all in your head?

Color temperature is just half of the equation. Equally important is another number: the Color Rendering Index, or CRI. Daylight and incandescent bulbs set the standard here, with a CRI of 100. That means the human eye perceives all the colors of the spectrum equally well under either daylight or incandescent bulbs.

As for fluorescent bulbs? There's still progress to be made. The best have a CRI of 95. You can think of that as exaggerating some colors -- ours seem to bring out yellows -- while downplaying others, such as blues. This, of course, subtly changes the color palette you perceive in a room.

Unfortunately, while more CFLs are coming with color temperature printed on the base of the bulb or on the packaging, we haven't seen any CRI numbers yet, so it will take a bit of digging to determine which bulbs are better than others.

The bottom line is that all those folks who insist that incandescent bulbs are better than CFLs may have a point: the question is whether the difference is worth using 3 times as much energy.

Illustration by Jonathan Bean using information from the latest issue of Environmental Building News

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