Canon EOS Rebel SL1 18-55mm IS STM Kit Instruction Manual page 133

[Auto]
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 in most cases.
[Enable]
Noise reduction is performed for all exposures of 1 sec. or longer.
The [Enable] setting can reduce noise that cannot be detected with
the [Auto] setting.
With [Auto] and [Enable], the noise reduction process after the picture is
taken may take the same amount of time as that for the exposure. You
cannot take another picture until the noise reduction process is
completed.
Images taken at ISO 1600 or higher may look grainier with the [Enable]
setting than with the [Disable] or [Auto] setting.
With [Auto] and [Enable], if a long exposure is shot with the Live View
image displayed, "BUSY" will be displayed during the noise reduction
process. The Live View display will not appear until the noise reduction is
completed. (You cannot take another picture.)
Set the desired setting.
2
Select the desired setting, then press
<0>.
The setting screen closes and the
menu will reappear.
Take the picture.
3
The image will be recorded with noise
reduction applied.
3 Setting Noise ReductionN
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