Canon EOS 5D Mark III Instruction Manual page 168

q Selecting the Metering ModeN
When <r> is set, <h> can be displayed in the viewfinder (p.318).
168
Spot metering
r
This is for metering a specific spot of the subject or
scene. The metering is weighted at the center
covering approx. 1.5% of the viewfinder area.
Center-weighted average metering
e
The metering is weighted at the center and then
averaged for the entire scene.