Apple Color 1.0 - Manual (Page 27)

Chapter 1 Color Correction Basics 27
Most of the media you’ll receive falls into one of the following bit depths, all of which
Color supports:
 8-bit: Most standard and high definition consumer and professional digital video
formats capture 8-bit image data, including DV and DVCPRO-25, DVCPRO 50, HDV,
DVCPRO HD, HDCAM, and so on.
 10-bit: Many video capture interfaces allow the uncompressed capture of analog and
digital video at 10-bit resolution.
 10-bit log: By storing data logarithmically, rather then linearly, a wider contrast ratio
(such as that of film) can be fit into a 10-bit data space. 10-bit log files are often
recorded from datacine scans using the Cineon and DPX image sequence formats.
 16-bit: It takes 16 bits of linear data to match the contrast ratio that can be stored
with 10-bit log. Since linear data is easier for computers to process, this is another
data space that’s available in some image formats.
Higher bit depths accommodate more image data by using a greater range of numbers
to represent the tonal range that’s available. This is apparent when looking at the
numeric ranges used by the two bit depths most commonly associated with video.
 8-bit images use a full range of 0–255 to store each color channel (Y´C
B
C
R
video uses
a narrower range of 16–235 to accommodate super-black and super-white). 255 isn’t
a lot of values, and the result can be subtly visible “stairstepping” in areas of the
picture with narrow gradients (such as skies).
 10-bit images, on the other hand, use a full range of 0 to 1023 to store each color
channel (again, Y´C
B
C
R
video uses a narrower range of 64–940 to accommodate
super-black and super-white). The additional numeric range allows for smoother
gradients, and virtually eliminates bit-depth related artifacts.
Fortunately, while you can’t always control the bit depth of your source media, you can
control the bit depth at which you work in Color independently. That means that even
if the source media is at a lower bit depth, you can work at a higher bit depth to make
sure that the quality of your corrections is as high as possible. In particular, many
effects and secondary corrections look significantly better when Color is set to render
at higher bit depths. For more information, see “
Playback, Processing, and Output
Settings ” on page 106.
Basic Color and Imaging Concepts
Color correction involves controlling both an image’s contrast and its color (exercising
separate control over its hue and saturation). This section explains these important
imaging concepts so that you can better understand how the Color tools let you alter
the image.