Canon EOS Rebel SL3 DSLR Camera with 18-55mm Lens (Black) - Manual (Page 449)

449
C.Fn-4 Exposure compensation auto cancel
0: Enable
When you set the power switch to <
2
>, the exposure compensation
setting will be canceled.
1: Disable
The exposure compensation setting will remain in effect even if you set
the power switch to <
2
>.
C.Fn II: Drive
C.Fn-5 Mirror lockup
0: Disable
1: Enable
You can prevent the camera vibration blur due to the mechanical
vibrations (mirror shock) inside the camera during shooting with super
telephoto lenses or shooting close-ups (macro photography). See
page 165 for the mirror lockup procedure.