Apple Color 1.0 - Manual (Page 177)

Chapter 9 Primary In 177
Important: When you expand the contrast of underexposed shots, or make other
extreme contrast adjustments, you may accentuate film grain and video noise in the
image. This is particularly problematic when correcting programs that use video
formats with low chroma subsampling ratios. for more information, see “
Chroma
Subsampling ” on page 25.
Of course, you also have the option to lower the contrast ratio of an image. This might
be done as an adjustment to change the apparent time of day (dulling shadows while
maintaining bright highlights for a noon-time look), or simply as a stylistic choice
(lighter shadows and dimmer highlights for a softer look).