Last night I had the pleasure of shooting the band 7 Year Punk, featuring a very young musician named Cash.  Cash is 7, and was invited to open for the band Askultura.  

During the show the lighting tech turned on what most concert photographers dread, red lights.  To understand why this is bad, you need to understand how a camera sees the world; in combinations of red, green and blue.  On most DSLR cameras, the sensor has what is called a Bayer Matrix, or Bayer array. The Bayer matrix is an alternating set of colors of red, green and blue filters overtop the pixels of the camera. Red filters allow only red, blue only blue, and so forth.  The camera uses a sophisticated algorithm to extrapolate other colors from the intensity of each channel and their location.   When the red lights flare on-stage, this has several effects.  The first is that the red channel is saturated, or filled to the point of excess, and everything becomes red to the point of excess.  The second thing that happens is that color data for the rest of the scene is lost, or overwritten to red.  The third thing that happens is that the camera usually doesn't light meter the scene properly, and you get a glowing effect on anything in the red lights.  

Now, there are several options for dealing with this:

1)  Reduce the intensity of the red channel in camera.  In camera, this means taking a scene that under other circumstances would be exposed normally, and underexposing it.  You'll end up losing detail and background images of anything that isn't being hit directly with a light, but your subjects will be much more aesthetically balanced, albiet red.

2) Reduce the intensity of the red channel in post processing.  Lightroom and photoshop allow for independent control of your color channels (assuming you shot the show in RAW format).  I personally feel this leads to flat, grayish images.  I might not be processing them properly.

3) Adjust the white balance of the entire image in Lightroom.  You can use the eye dropper and a white/gray spot in the photo to set a custom white balance, or you can take your chances with the auto-balance feature.  Or just adjust the color slider towards the blue side until you've evened out the red.  This will throw off colors that are lighted normally however.  

4) Mask the red areas in photoshop and apply white balance corrections to those images only.  Time consuming, and truthfully I've never bothered to do it in the past because I haven't had a working copy of photoshop until now. 

5) Convert the image to gray scale. Personally, I feel this is a crutch, but if you need working images...

6)  Hat tip to www.Ishootshows.com for this one... bribe the lighting tech to turn the lights off.

I'll try and get more detailed examples of how to deal with red lights up in a later post.