March 11, 2010


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Kind of blue
The world is changing color
By John “jaQ” Andrews

It’s becoming more and more noticeable. In a world that used to be all yellow, it’s starting to look pretty blue.

No, I don’t mean we’re all going from being cowardly to depressed. I’m talking about the color of our “white” light bulbs, from standard indoor lamps to streetlights, car headlights and even strings of Christmas lights. The mini incandescent bulbs of yore had a distinctly yellowish tinge to them, but who ever noticed? They were all the same color, and that was good enough for us.

Now that LEDs are gaining popularity for their energy efficiency, and they spent the holidays displayed alongside incandescent strings, the difference is glaringly obvious. How can they sell us two completely different colors and call them both white?

The answer lies in the bulbs’ “color temperature.” That’s the measure used to describe the quality of light, and is based on a theoretical object that’s perfectly black at absolute zero. The idea is that as that object warms up, its temperature in Kelvins corresponds to the color it gives off, like an electric heating element turning red as it gets hotter.

LED lights — at least the cheaper ones — tend to have a color temperature around 5000K, while incandescent lights are around 3000K. Daylight on Earth — not the color of the Sun itself, but daylight once it travels 93 million miles and is scattered by our atmosphere — runs between 5000K and 6500K. That means LEDs, while sometimes jarring to look at because they’re not what we’re used to, actually produce illumination closer to natural sunlight.

Digital cameras and monitors make use of this measurement as well. Generally speaking, the higher you can set your monitor’s color temperature, the whiter things will look. Set it to 6500K and the white background in your word processing program should look pretty similar to a piece of paper outside on an overcast, evenly-lit day. Crank it up to 9300K and that same white background will be a more bluish superwhite.

In digital cameras, it’s used in the “white balance” setting. Most modern cameras set white balance automatically so colors look natural and are represented accurately, but many allow you to set it manually as well. This might  be done by dialing in numbers or by pointing the camera at a white object to let the camera know, “Hey! That’s white! Adjust all your other colors accordingly!” This is particularly useful in odd or low lighting situations.

Any budding pyromaniac in a high school physics class will tell you that red flames are really the coldest. Closer to the center of a flame, you get blue light, and at the very core is the “white hot” white. Stupid humans that we are, though, we tend to associate blues with cold (think water and even the ultrawhiteness of snow) and reds, oranges and yellows with warmth (like fire). For that reason, raising the color temperature in a graphics program makes an image look “cooler” and lowering it makes it look “warmer.”

Similarly, you can buy “cool white” incandescent light bulbs that have more of a bluish tinge as well as “warm” LEDs that are made to look more like older, yellower incandescents. If you’re a stickler for having all the lights in your house be the same color, this might be important enough to you to pay the price premium those modified products demand.

Or maybe you just want your computer screen to look right.