The main reason green is currently the most popular keying color is that the green channel in composite video has the highest luminance value of the three signal colors red, green, and blue (RGB). The green channel in HD digital video has the most samples of the three available channels, so it gives you more data to work with, with the least amount of noise. In today's more advanced HD digital video cameras, this is typically known as 4:2:2. That means there are twice as many green photosites on a Bayer pattern sensor than there are red or blue (RGB = 4:2:2), as shown in the diagram in Figure 2.1. You can read more about the different camera sensors and digital camcorder technology in Chapter 11.