Canon EOS50D EOS 50D Instruction Manual - Page 181

3 Custom Function SettingsN It is best to make the adjustment at the actual place to be photographed. This will make the adjustment more precise. With setting 2, if an Extender is used, the adjustment will be registered for the lens and Extender combination. The registered AF microadjustments will be retained even if you use the Custom Function to clear all settings (p.172). However, the setting itself will be [0: Disable]. C.Fn IV: Operation/Others C.Fn IV -1 Shutter button/AF-ON button 0: Metering + AF start 1: Metering + AF start/AF stop During autofocusing, you can press the button to stop the autofocusing. 2: Metering start/Metering + AF start This is useful for subjects which keep moving and stopping repeatedly. In the AI Servo AF mode, you can press the button to start or stop the AI Servo AF operation. The exposure is set at the moment the picture is taken. Thus, the optimum focusing and exposure will always be achieved as you wait for the decisive moment. 3: AE lock/Metering + AF start Convenient when you want to focus and meter at different parts of the picture. Press the button to meter and autofocus, and press the shutter button halfway to attain AE lock. 4: Metering + AF start/Disable The button will not function. C.Fn IV -2 AF-ON/AE lock button switch 0: Disable 1: Enable The functions of the and buttons will be switched with each other's function. When set to 1, press the button to display the image index or to reduce the image display. 181