Apple Color 1.5 - Manual (Page 147)

Because of this, you may occasionally notice differences between images that were
initially corrected at less than 16-bit, and the same images changed to render at Floating
Point. This is particularly true in the Color FX room.
For more information about bit depth, see How Do Bit Depth and Channel Data
Correspond?
How Do Bit Depth and Channel Data Correspond?
The actual range of values used by each channel for every pixel at a given bit depth is
calculated by taking 2 to the nth power, where n is the bit depth itself. For example, the
range of values used for 8-bit color is 2 to the 8th power, or 256 values per channel. The
range of values for 16-bit color is 2 to the 10th power, or 65536 values per channel.
However, this isn't the whole story. How much of the available numeric range is actually
used depends on how the image data is encoded.
• Full Range: Image data using the RGB color space encodes each color channel using
the full numeric range that's available. This means that 8-bit video color channels use
a value in the range of 0–255 and 10-bit channels use a range of 1–1023.
• Studio Range: 8- and 10-bit video image data that's stored using the Y
′
C
B
C
R
color space
uses a range of values for each channel. This means that a subset of the actual range
of available values is used, in order to leave the headroom for super-black and
super-white that the video standard requires.
For example, the luma of 8-bit Y
′
C
B
C
R
uses the range of 16–236, leaving 1–15 and
235–254 reserved for headroom in the signal. The luma of 10-bit Y
′
C
B
C
R
uses the range
of 64–940, with 4–63 and 941–1019 reserved for headroom.
Furthermore, the lowest and highest values are reserved for non-image data, and the
chroma components (C
B
and C
R
) use a wider range of values (16–240 for 8-bit video,
and 64–960 for 10-bit video).
Auto Save Settings
Two settings let you turn on or off automatic saving in Color.
• Auto-Save Projects: Turning this option on enables automatic saving.
• Auto-Save Time (Minutes): Specifies how many minutes pass before the project is saved
again. This is set to 5 minutes by default.
147 Chapter 5 Configuring the Setup Room