Canon EOS RP Instruction Manual page 367

Long Exposure Noise Reduction
For images exposed for 1 sec. or longer, noise (dots of light and banding)
typical of long exposures can be reduced.
[AUTO] Automatic
z
For exposures of 1 sec. or longer, noise reduction is performed
automatically if noise typical of long exposures is detected. This [Auto]
setting is effective enough in most cases.
[ON] Enable
z
Noise reduction is performed for all exposures of 1 sec. or longer. The
[Enable] setting may reduce noise that cannot be detected with the [Auto]
setting.
1
Select [z: Long exp. noise
reduction].
2
Set a reduction option.
3
Take the picture.
The image will be recorded with noise
g
reduction applied.
Setting Noise Reduction
159