Apple Final Cut Express 4 - Manual (Page 818)

818 Part IX Effects and Color Correction
Multiply
Multiply emphasizes the darkest parts of each overlapping image, except that
midrange color values from both images are mixed together more evenly. Progressively
lighter regions of overlapping images become increasingly translucent, allowing
whichever image is darker to show through. Whites in either image allow the
overlapping image to show through completely. Blacks from both images are
preserved in the resulting image.
The order of clips affected by the Multiply composite mode does not matter.
Suggested uses: The Multiply composite mode is particularly useful in situations where
you want to knock out the white areas of a foreground image and blend the rest of the
image with the colors in the background. For example, if you superimpose a scanned
sheet of handwritten text over a background image using the Multiply composite
mode, the resulting image becomes textured with the darker parts of the foreground.