Canon EOS R50 Advanced User's Manual page 197

Note
AE lock is not possible with bulb exposures.
Effect of AE Lock
Metering Mode
Selection
* Center-weighted exposure is locked when [
focusing ( ).
Automatic Selection
Exposure centered on the AF point in
focus is locked.
Center-weighted exposure is locked.
AF Point Selection
Exposure centered on the selected AF
point is locked.
] is set with the camera configured for manual
197
Manual Selection