[Greg McKaskle]

The white paper last year used a string of indoor LED Christmas lights inserted into foam. They were red LEDs. This year, the paper points out some products from SuperBrightLEDs.com, which, while designed for cosmetic purposes, work quite well as ring lights. I've tested green, red, amber, and blue. All colors can be made to work provided you get the white-balance and exposure settings such that the reflected colors are very saturated.

If you choose to avoid the color masking and simply go with a brightness threshold to form the mask, it doesn't matter what color you use, and you can even mix colors or use a white light. The LV example vision code for 2012 shows both color and brightness approaches. For brightness, it also sets the camera to disable color, receiving a monochrome image directly from the camera.

Greg McKaskle