Lame Emitting Diodes: LED Lights Cause Problems for Digital Concert Photography

I was taking pictures of a band in a bar last night, and I ran across a rather interesting phenomenon. The band had set up some newfangled LED stage lights on either side of the stage. These were vertical banks of red, green, and blue LEDs that would cycle through color patterns to create a dynamic effect on the band. Inexpensive LEDs are revolutionizing all sorts of lighting scenarios, and club lighting is just one of them. But something strange was happening. One of the musicians with a saxophone was standing right next to an LED light bank. I saw amazing swirls of red, green, and blue in the brass of his horn, so I moved in to capture that in a photograph. But, the photograph I took showed nothing but a nice even white light. Verrrry interesting, I thought. I wondered if there was some sort of flickering with the LEDs that was invisible to the naked eye but not the camera sensor. I came home and started digging on le interwebs, and while I didn’t find the exact answer, I did come across some interesting info. Basically, the opposite was happening.

Unlike incandescent bulbs with a colored gel, LEDs emit light along a very narrow frequency. A blue LED is really very pure blue. A red LED is very pure red. This is not a huge deal to our eyes because we can handle it pretty well, but digital camera sensors are a bit trickier. In researching LED effects on camera sensors, I came across a fascinating discussion that shed some light on other issues I’d encountered in concert photography. If you’ve anything of a technical mind, you can dig through this thread on candlepowerforums.com. (A guy named Vincent Tseng has done a lot of thinking about this. Props to him for his action in that thread) Now, I will try to sum it up briefly as best I can: It so happens that the vast majority of digital camera sensors are arranged in such a way that half the sensor is devoted to capturing green light. (See a Bayer filter explanation on Wikipedia) The other half is evenly divided to red light and blue light. (You’ll recall that various mixtures of R G & B light will give us pretty much any color we should wish to see.) In the real world, pretty much every color is a recipe of some mixture of red, green, and blue. Camera sensors pick up each color separately and then the processor remixes them back into the image we saw in the first place. It’s all very clever for most everything you want to take a picture of.

But, enter LED lights. The frequency of LEDs being so pure can actually be problematic for camera sensors. This is very clearly seen when these LED stage lights shine pure blue, pure red, or even pure blue+red (magenta) on a subject. Since this light has no green at all in those hues, half the digital camera sensor is rendered useless. The practical result is that a person illuminated in this pure non-green LED light will have a cartoonish flat face — or at least a lot of banding where the digital image will shift from one color abruptly to another with nothing inbetween — because the sensor isn’t picking up enough visual information in those areas. This is how I understand it anyway, I’m not an optical engineer, but I do know a little physics.

Back in my old life of frequenting concerts and clubs to shoot musical happenings I was always vaguely aware of certain club lighting that would result in crappy photographs. Now I know why. The former Spaceland was the worst, since the LED banks were often all that was being used.

Here’s a shot of the band Castledoor which I rejected because the light made the singers face look plastic. At the time, I just chalked it up to low light in general, but now I know that the LED lighting contributed to the flat cartoonish magenta.

So does this explain my phantom rainbows in a saxophone which I couldn’t capture? I’m guessing yes. I’m thinking my sensor was having trouble seeing the three “pure” red green and blue frequencies that my eye was enjoying and saw a whiter light than my eye did. I’ve still not got my head around it entirely, but there is something to it for sure.

I do find it humorous that the gear toted around by your basic concert photographer is getting more and more technically advanced — and more and more expensive. Meanwhile, the miraculous “cheap LED” that is making cool lighting effects available to more and more venues and bands is conspiring to make concert photos worse and worse.

There is a type of digital camera sensor known as the Foveon sensor that appears most notably in the Sigma DP2. As I understand it, this sensor should be less susceptible to that sort of thing, but I haven’t seen any real examples. I can imagine a market-opportunity for someone to come up with a phased filter of some sort for LED-illuminated photography.

And, of course, this should not be a problem at all for your trusty film camera. But, have fun shooting enough frames of film to get the perfect concert moment, Richie Rich. I am very curious and may one day borrow an LED stage light and run some side-by-side shots with digital and film.

So, what to do in the meantime? Well, shoot RAW as much as possible to capture as much information as your camera can. RAW won’t make the problem go away, but shooting only JPEG makes it even worse. Keep an eye on how the stage lighting changes and really go for those times when the light mix is NOT pure red or blue or magenta. Also, black and white conversions can occasionally save a washed out magenta shot. I hope this helps! If you have other ideas, please leave a comment.

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