How to Correct an LED “White” Light Source
I really love my LED ring light, which I use for macro photography. It’s just one example of photographic lighting based upon white LED technology. These lights are great, because they don’t heat up (no wilting flowers), they last a really long time, they’re small, and they consume much less energy.
But there’s a slight downside. They put out kind of weird light. None of my cameras can quite figure out a good "auto" white balance for them. The reason for this problem is the blue part of the light spectrum. Most, if not all, LED ‘white’ lights put out an unbalanced spectrum that takes a special white balancing procedure.
“White” light LED typical spectrum. Lots of blue, little red.
Camera Auto White Balance just doesn’t cut it
My camera “auto white balance” isn’t smart enough to get the color of a grey card correct using the white LED light.
Using the Capture NX-D gray point “eye dropper” isn’t enough to fix it. Still too blue.
It’s tempting to just use the little “gray point” eye dropper to fix the color, but this isn’t quite enough. The histogram above shows how there’s still too much blue.
Manually increasing the color temperature helps, but it’s still too blue
Additional blue adjustment (10000K plus Levels and Curves adjust) finally looks correct
Capture NX2: adjust color temperature and adjust color balance as well
Capture NX2 with 10000K and Blue -40 also gets me the correct grey
As shown in the pictures above, it’s the norm for LED white lights to put out excessive blue light, while skimping on the red light. The camera single white-balance adjustment isn’t able to fix the problem. The image editor simple gray-point color-picker still leaves too much blue in the shot.
In an image editor, however, you can fix the problem with a double adjustment. For this LED light, I start with a high color temperature (roughly 10,000K) to align the Red and Green channels. (Use a grey card image, of course!). Second, shift the blue peak until it lands on top of the red and green peaks. It probably won't be perfect, but it will be plenty close to look good.
There are so many occasions where you need to adjust your white balance. Please, please invest in a grey card. They’re really dirt cheap and can greatly improve the look of your pictures, especially when you get into environments with unusual lighting.
If I were smart, I’d save these color adjustments as a batch file, so that I could correct all of the pictures shot using the LED light at once. A batch file is also a good idea if you tend to forget after a few months exactly how you corrected the white balance in the first place.
Don’t avoid getting a white LED light for photography, just because you’ve heard that their color is bad. Chances are that you can correct the color in post-processing by using a two-step procedure. Chances are less good that you can correct the white balance in-camera, so jpeg shooters beware.
My LED ring light in action