Canon EOS M50 Mark II Advanced User's Manual page 255

Caution
Precautions when set to [Multi Shot Noise Reduction]
If there is significant misalignment in the image due to camera shake, the noise
reduction effect may become smaller.
Be careful about camera shake in handheld shots. Using a tripod is recommended.
If you shoot a moving subject, the moving subject may leave afterimages.
Auto image alignment may not function properly with repetitive patterns (lattice,
stripes, etc.) or flat, single-tone images.
If the subject's brightness changes as the four consecutive shots are taken,
irregular exposure in the image may result.
After shooting, it may take some time to record an image to the card after
performing noise reduction and merging the images. [BUSY] is displayed on the
shooting screen during image processing. Shooting is not possible until processing
is finished.
[Multi Shot Noise Reduction] is not available when features such as these are
set: bulb exposures, AEB or WB bracketing, RAW or RAW+JPEG shooting, long
exposure noise reduction, or Creative filters.
Flash photography is not available. Note that the AF-assist beam may be fired,
depending on the [ : AF-assist beam firing] setting.
[Multi Shot Noise Reduction] is not available (not displayed) when recording
movies.
Automatically switches to [Standard] if you set the power switch to < >,
replace the battery or card, or switch to Basic Zone modes, bulb exposure, or
movie recording.
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