Canon EOS-1D X Mark II DSLR Camera (Body Only) - Manual (Page 190)

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This function reduces the noise generated in the image. Although noise
reduction is applied at all ISO speeds, it is particularly effective at high
ISO speeds. When shooting at low ISO speeds, the noise in the darker
parts of the image (shadow areas) can further be reduced.
1
Select [High ISO speed NR].
Under the [ z 2 ] tab, select [ High ISO
speed NR ], then press < 0 >.
2
Set the level.
Select the desired noise reduction
level, then press <
0 >.
3
Take the picture.
The image will be recorded with noise
reduction applied.
3
Setting Noise Reduction
High ISO Speed Noise Reduction