The EOS 50D has a high-precision 9-point wide area AF that uses cross-type points at f-stops of f/5.6 or faster, enabling the camera to focus faster, more accurately, and in difficult lighting situations. AF sensitivity is a stunning EV-0.5 to EV18. Adding to this AF performance, the EOS 50D incorporates a diagonally mounted cross-type sensor that is sensitive to both vertical and horizontal lines at f/2.8, perfect for enhanced operation in dim light. The EOS 50D has a number of focus modes, including One-Shot AF, AI Focus AF and AI Servo AF.
With some lenses, the peripheral AF points may become sensitive to either vertical or horizontal lines (they will not function as cross-type AF points). These lenses are: EF 35-80mm f/4-5.6, EF 35-80mm f/4-5.6 II, EF 35-80mm f/4-5.6 III, EF 35-80mm f/4-5.6 USM, EF 35-105mm f/4.5-5.6, EF 35-105mm f/4.5-5.6 USM, EF 80-200mm f/4.5-5.6 II, EF80-200 f/4.5-5.6 USM.