In my Times column Thursday, I reviewed a new generation of LED light bulbs. They last 25 times as long as regular bulbs, use maybe one-eighth the electricity, work with dimmers, turn on instantly to full brightness and remain cool to the touch. A big drawback has always been cost, but now, I noted, the prices have fallen.

This column generated a lot of reader e-mail, probably because LED represents change. And change is always scary. Here are some excerpts, with my responses.
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* For LED bulbs, the biggest issue that most consumers will notice is the color. You correctly point out that you can get different colors, and also different shades of white, from warm white, to cool white, to daylight. However, not all white is the same. Two bulbs, both of which measure 2700K (warm white) color may create a completely different impression in the room.

The difference is C.R.I. (Color Rendering Index). Incandescent bulbs have a C.R.I. of 100. Really bad LEDs have a C.R.I. of 50; average ones (most of them) have a C.R.I. of 80 to 85. The really good ones have C.R.I.’s above 90.

C.R.I. is a way of expressing how many colors in the rainbow are actually contained in the white light. Incandescent bulbs contain every color in the rainbow, all in equal measure.

With LED bulbs that have low C.R.I.’s, the color of objects looks wrong, and everything “feels” ghostly. It is not a subtle effect.

Wow. Well, I’d never heard of C.R.I., and it certainly isn’t listed on the package.

I can say only that I’m completely happy with the light color of the Cree bulbs. They look nothing like the weak, diluted light of the compact fluorescents they’re going to replace. I don’t perceive anything ghostly or wrong about them.

But if you’re worried about C.R.I, maybe try out one bulb at home before you replace the whole house’s bulbs.

* Why I don’t have LED bulbs: I have yet to see one that puts out close to the same lumens of an incandescent bulb rated at 75 or 100 watts offered for sale in my area.

Many of you made this point: that the 40- and 60-watt bulbs I reviewed are not bright enough for aging eyes, reading, detail work and so on.

That really is a good point. You can buy 75- and 100-watt-equivalent LED bulbs — online, they’re plentiful — but they’re still expensive ($30 to $45 each).

* At my home, CFLs don’t last half as long as stated on the box, and when CFL electronics flame out, they leave that nasty burnt electronics smell, strongly disliked by my wife. A few friends have reported CFL flame outs that have set things on fire.

Sorry to hear that! However, my column was about LED lights, not compact fluorescent light bulbs. Compact flourescents are basically curlicue tubes filled with gas that lights up. LED bulbs use tiny light-emitting diodes, of the type you have seen in some flashlights and the “flashes” of smartphones.

* Why didn’t you write up the LIFX bulbs on Kickstarter? Are you some kind of paid shill for the light-bulb industry?

Mainly, because I hadn’t heard about LIFX bulbs. Now I have!

Looks like it’s a lot like the Philips Hue kit I reviewed, in that these are LED bulbs you can control from a phone app: brightness, timing and color. The beauty of LIFX, though, is that there’s no router box required. The networking electronics are right in the bulb.

And the LIFX does more, too: changes color in time to the music, for example, or notifies you when you have new e-mail.

These bulbs did super-well on Kickstarter, so they’ve obviously captured the public’s imagination. I’m in touch with the creators, and they’ve promised to send me one to try out when it becomes available!

* You have done what many before have done: Praise LED light bulbs — without touching on the quality of light.

It doesn’t matter whether the light bulb is $200 or 50 cents. If the light is ugly, and it hurts your eyes to read, then why should I buy it?

Compact fluorescent lights have an austere blue tinge. Some give a “warmer” shade of yellow. But the quality of light they produce is atrocious.

I did, in fact, mention the quality of light; in my opinion, it’s wonderful. You can choose “daylight” (whiter) or “warmer” (yellower). With some, like the Philips, you can dial up any color you like: white with a touch of blue or yellow, say.

But I’m not sure why we keep talking about compact fluorescent lights. LED technology is completely different. There is zero relationship between a compact fluorescent light bulb’s light quality and LED’s light quality.

* You neglected an important point: because of heat issues, you’re not supposed to put LED bulbs into enclosed fixtures, like ceiling “cans.”

Actually, I asked Cree specifically about this. The representative says the bulbs are fine in ceiling cans. “The Cree LED bulb can be used in any application that would use an incandescent bulb. As long as there is an opportunity for air to circulate, the bulb is designed to work properly.”

I’m aware that not all bulbs meet this criterion; I’ve seen warnings on 3M and Philips bulbs, for example, not to use them in ceiling cans.

* Is there a potential issue with RF (radio frequency) interference from the circuitry? I know someone who put the LED bulbs in his garage door opener and then had trouble with the remote control.For more information, please visit cree led flashlight