Canon EOS Rebel T6i W Instruction Manual page 158

q Changing the Metering ModeK
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 at the moment the picture is taken. (Pressing the
shutter button halfway does not lock the exposure.)
158
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.