Canon EOS-1D X Mark III EOS-1DX Mark III Advanced User Guide - Page 227

Evaluative metering General-purpose metering mode suited even for backlit subjects. The camera adjusts the exposure automatically to suit the scene. Partial metering Effective where there are much brighter lights around the subject due to backlight, etc. Spot metering Effective when metering a specific part of the subject. The spot metering circle will be displayed in the viewfinder. Center-weighted average Metering over the entire area is averaged, with the center of the viewfinder weighted more heavily. Note By default, the camera will set the exposure as follows. With < >, holding down the shutter button halfway locks the exposure value (AE lock) after the camera focuses with One-Shot AF. With the exposure value is set at the moment the picture is taken (without locking the exposure value when the shutter button is pressed halfway). You can link spot metering to all AF points by setting [ 1: Spot meter. linked to AF pt] to [Linked to active AF point] ( ). With [ 2: AE lock meter. mode after focus] ( ), you can set whether or not to lock the exposure (AE lock) when focus is achieved with One-Shot AF. 227