Apple Final Cut Express HD - Manual (Page 780)

780 Part IX Effects
Working With Composite Modes
Final Cut Express HD composite modes determine how the brightness and color of one
clip visually interact with those of another clip layered beneath it in a sequence. When
you edit a clip into your sequence, it defaults to the Normal composite mode, meaning
that it is a completely opaque layer that does not blend with the layers beneath.
How Composite Modes Affect Images
Composite modes mix colors from overlapping images together based on the
brightness values within each color channel in an image. Every image consists of red,
green, blue, and alpha channels (or one luma and two chroma channels in the case of
Y´C
B
C
R
component video). Each individual channel contains a range of brightness
values that define the intensity of each pixel in the image that uses some of that color.
The effect that each composite mode has on objects that overlap in the Canvas
depends on the range of color values within each object. The red, green, and blue
channels (or Y´C
B
C
R
channels) within each overlapping pixel are mathematically
combined to yield the final image.
These value ranges can be described as blacks, midrange values, or whites. These
regions are loosely illustrated by the chart below.
For example, the Multiply composite mode color values that fall into the white areas
of an image are rendered as transparent, while the black areas of the image are left
alone. All midrange color values become translucent, with colors falling into the
lighter end of the scale becoming more transparent than the colors that fall into the
darker end of the scale.
Important: Final Cut Express HD composite modes work in conjunction with a clip’s
Opacity parameter. The composite mode you select determines how the color values of
one clip interact with those in the clip beneath it. Additional changes made to a clip’s
opacity can lighten or intensify this effect.
Blacks Whites Midrange color values