Canon EOS RP Mirrorless Camera - Manual (Page 160)

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Setting Noise Reduction
o With [Auto] or [Enable] set, the noise reduction process after the picture is
taken may take the same amount of time as that for the exposure.
o Images may look grainier with the [Enable] setting than with the [Disable] or
[Auto] setting.
o [BUSY] is displayed as noise is reduced, and the shooting screen is not
displayed until processing is finished, when you can shoot again.