Canon EOS 5D Mark III Instruction Manual (en)

Basic Operation
The shutter button has two steps. You can press the shutter button 
halfway. Then you can further press the shutter button completely.
Pressing halfway
This activates autofocusing and the 
automatic exposure system that sets the 
shutter speed and aperture.
The exposure setting (shutter speed and 
aperture) is displayed in the viewfinder 
and on the LCD panel (0).
Pressing completely
This releases the shutter and takes the 
Preventing Camera Shake
Hand-held camera movement during the moment of exposure is called 
camera shake. It can cause blurred pictures. To prevent camera shake, 
note the following:
• Hold and steady the camera as shown on the preceding page.
• Press the shutter button halfway to autofocus, then slowly press the 
shutter button completely.
Shutter Button
In the d/s/f/a/F modes, pressing the <p> button will 
execute the same operation as pressing the shutter button halfway.
If you press the shutter button completely without pressing it halfway first 
or if you press the shutter button halfway and then press it completely 
immediately, the camera will take a moment before it takes the picture.
Even during menu display, image playback, or image recording, you can 
instantly go back to shooting-ready by pressing the shutter button