Canon EOS R3 Advanced User's Manual page 136

Note
In [ ] mode with ISO Auto, [ ] (evaluative metering), and [ : AE lock meter.
mode after focus] set to the default setting ( ), holding down the shutter button
halfway locks the ISO speed after the camera focuses with One-Shot AF.
When ISO Auto is set, you can press the < > button to lock the ISO speed.
If you press the < > button and recompose the shot, you can see the exposure
level difference on the exposure level indicator compared to when the < >
button was pressed.
Any existing exposure compensation amount is maintained if you switch to [ ]
mode with ISO Auto after using exposure compensation in [ ], [ ], or [ ]
mode ( ).
To coordinate exposure compensation in ½-stop increments with ISO speed set in
⅓-stop increments when [ : Exposure level increments] is set to [1/2-stop] and
used with ISO Auto, exposure compensation is further adjusted by adjusting shutter
speed. However, the shutter speed displayed will not change.
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