To the human eye, light can appear both very bright and very colorful. Imagine a sunny landscape or a storefront lit by a neon sign; they are bright and colorful! However, a camera captures a range of contrast that is much narrower and not as intelligently selected such that the sunny landscape or neon-lit storefront can look washed-out. This problem of poorly controlled contrast is especially bad in cheap cameras and cameras that have small sensors, as webcams do. As a result, bright light sources tend to be imaged as big white blobs with thin rims of color. Moreover, these blobs tend to take the shape of the lens's iris, typically a polygon approximating a circle.

The thought of all lights becoming white and circular makes the world seem like a poorer place, if you ask me. Nonetheless, in computer vision, we can take advantage of such a predictable pattern. We can look for white blobs that are nearly circular, and we can infer their human-perceptible color from...