White Balance is all about the color of light, and the best reason to shoot RAW is the freedom to adjust the white balance with great power in post production. But what’s up with Lightroom’s White Balance Slider? Why is it backwards?
Keep Cool, Like 2000 Kelvin
If you’ve shot in RAW, you’ll notice the top white balance slider has a number on the right, and that represents the color temperature in kelvins (if you’re working with .jpg files, then you see a number from -100 to 100, but the affect is the same). A really orange light, like a sixty watt lightbulb or those orange street lamps, can be described with a low number, like 2000 kelvins. A really blue light is a higher color temperature, like 7000. Just think of a Bunsen burner–it’s not as hot when it’s an orange flame, and it’s really hot when it’s a blue flame. (Geek Note: don’t say, “2000 degrees kelvin,” because the Kelvin scale isn’t measured in degrees; it’s measured in kelvins. Just say, “2000 kelvin.” You’ll make your physics teacher proud.)
But why does my picture turn blue when I set the slider to the left at 2000 kelvin? It’s a funny thing, but this is simply because if you shot under an orange light that was 2000 kelvin, then that amount of Blue will correct for the orange and make the picture appear normal. Conversely, if the light was very blue, as you might have anytime the blue sky is your main light source (like on the shady side of a building), something like 7000 kelvin, then adding orange to the right side of the slider will counteract it. As I said, this makes your picture look normal.
Im All About That Blue
But “normal” is not a flattering word for photography. You can use white balance to achieve some stunning effects, all right inside the camera without Photoshop wizardry. For the photographs in this post, I set my camera white balance to the tungsten setting (which adds blue to correct for the very orange light from a 60 watt bulb), and then put an orange gel on my flash. Everything lit by the flash is balanced, but everything else has an extra blue tint added, and at dusk it makes a punchy portrait. Here’s an article with a little more depth about this technique.
Special thanks to Gary Forcier for suggesting this topic.