Canon EOS 100D Instruction Manual page 122

q Changing the Metering ModeN
With q (Evaluative metering), the exposure setting will be locked when you
press the shutter button halfway and focus is achieved. In the w (Partial
metering), r (Spot metering), and e (Center-weighted average metering)
modes, the exposure is set when the photo is taken. (Pressing the shutter
button halfway does not lock the exposure.) During Live View shooting, the
exposure is set at the moment the picture is taken, regardless of the
metering mode.
122
Center-weighted average metering
e
The brightness is metered at the image center
and then averaged for the entire scene. This
metering mode is for advanced users.