The crayon mark on the lumber is then read by a grade reader. This consists of two cameras. One, a black and white camera, detects the shape of the mark and the other, a color camera, determines the color of the mark. Different symbols give the computer different commands and the computer then controls the trimmer, grade stamper, and sorter accordingly. Different graders use different color crayons to mark the lumber. The color camera allows the computer to keep track of each graders performance and the grader can be given more training in certain areas if needed.