Apple Final Cut Pro 7 - Manual (Page 1205)

The visible result is that darker color values in the background image intensify overlapping
areas in the foreground image, while lighter color values in the background image wash
out overlapping areas in the foreground image.
The order of two clips affected by the Overlay composite mode is important.
Boxes clip on top Monkey clip on top
Suggested uses: The Overlay composite mode is particularly useful for combining areas
of vivid color in two images.
Hard Light
Whites and blacks in the foreground image block overlapping areas in the background
image. Whites and blacks in the background image, on the other hand, interact with
overlapping midrange color values in the foreground image.
Overlapping midrange color values are mixed together differently depending on the
brightness of the background color values. Lighter background midrange values are
mixed by screening. Darker background midrange values, on the other hand, are mixed
together by multiplying.
The visible result is that darker color values in the background image intensify overlapping
areas in the foreground image, while lighter color values in the background image wash
out overlapping areas in the foreground image.
1205 Chapter 71 Compositing and Layering