Canon 60D explained in detail how to use the T-door in all gears.

C file: user-defined file, you can register settings, combined with shutter aperture ISO. If there are common parameter settings, define this file and save it. After the mode dial is transferred to this file, you can directly use the most commonly used parameters. M file: manual exposure file, which can set various parameters, but the longest shutter is 30 seconds. B: Similar to manual exposure, you can get the desired shutter speed. For example, deep space photography can be exposed for more than ten minutes and several hours. AV file: Aperture priority mode, which can freely adjust the lens aperture value, and the camera automatically adjusts the shutter speed. Television files; Shutter priority mode, freely adjust shutter speed, and the camera automatically adjusts aperture value. P file: the program automatically exposes, and the system automatically selects the appropriate shutter, aperture, ISO and other information. T-door: used when a specific shutter speed is required. The dial wheel can adjust the shutter speed, the aperture is automatically adjusted by the machine, and the sensitivity can be manually adjusted or set to automatic mode.