Apple Final Cut Pro 7 - Manual (Page 1198)

3 Adjust the opacity by doing one of the following:
• Drag the Opacity slider to the right or left.
• Click the arrows at the right and left of the Opacity slider.
• Type a percentage in the number field.
• Adjust the Opacity parameter’s keyframe graph line.
The pointer changes to the Adjust Line Segment pointer; a box shows the percentage
of opacity as you drag the keyframe graph line.
The opacity overlay in the Timeline can also be keyframed, enabling you to dynamically
change the opacity level over time. For information on keyframing, see
“Animating Motion
Effects Using Keyframes.”
Working with Composite Modes
Final Cut Pro 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
defines 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.
Blacks Whites Midrange color values
For example, the Multiply composite mode renders color values that fall into the white
areas of an image 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.
1198 Chapter 71 Compositing and Layering