Apple Final Cut Pro 5 - Manual (Page 1336)

Chapter 24 Rendering 549
III
Changing Render Settings
Each sequence has rendering options you can change in the following locations:
 Video Processing tab in Sequence Settings: This tab allows you to choose color space,
bit depth, maximum white level conversion, and scaling options for your sequence.
You can also adjust these settings in each sequence preset, using the Sequence
Preset Editor in the Audio/Video Settings window.
 Render Control tab in Sequence Settings: This tab allows you to choose render quality
settings, such as video quality and frame rate of rendered files. This allows you to
choose shorter rendering time with lower image quality, or vice versa.
These same settings are also available in the Render Control tab in User Preferences,
but in this case they only affect default settings for newly created sequences.
Overview of Video Processing Settings
The Video Processing tab determines how clips’ media files are processed within your
sequence. This affects color space conversions as well as the quality of motion
parameter animation.
About Color Space
Video and graphics files can represent color information several ways. Traditionally,
computer-generated video uses RGB pixels, while digital video from decks and
camcorders uses Y´C
B
C
R
(also known as YUV, or component video) pixels. These two
color spaces represent color information very differently.
RGB Color Space
In the RGB color model, colors are represented by red, green, and blue values in varying
amounts. When all three values are the same, the result is grayscale pixels. For example,
if all three color channels are 0, the pixel is black. If all three color channels are 255 (the
maximum value), the pixel is white.
Y´C
B
C
R
Color Space
In the Y´C
B
C
R
color model, a black-and-white channel called Y´, or luma, is derived from
the RGB color channels in a camcorder imaging chip. This Y´ channel represents the
brightness and detail of an image, and was originally created so that black-and-white
televisions could still receive useful information when color television was invented. Two
additional color channels, C
B
and C
R
(sometimes referred to as color difference channels
with names such as R-Y and B-Y, or U and V), are used to represent the color information.
Note: In digital video, the color channels are typically sampled less often than the luma
channel, reducing the video data without noticeable loss to the image. The ratio of
sampling between the Y´, C
B
, and C
R
channels is often notated as 4:2:2, 4:1:1, and so on,
depending on the sampling rates used. For more information about how color is
represented in various video formats, see Volume IV, Appendix A, “Video Formats.”