Apple Motion 2 Getting Started - Manual (Page 149)

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Extra Credit
As the last step in your introduction to Motion, learn
about keying and masking, audio, and how to export
your final project.
Keying and Masking
Blue and green screen shots are often used as elements in a motion graphics project.
In Motion, you apply keying filters to “pull” color keys. Keying filters remove a specified
color from an image and leave other colors intact. Masks are often used to help
remove areas of the image that the key alone did not remove, or to create specific
shapes that remove portions of an image. Keys and masks work by creating
transparency in areas of images so that images beneath the keyed or masked images
in the composite are visible.
This section provides a quick overview on using the Primatte RT filter to pull a basic key
in Motion, and applying masks to the matte pulled by the key. The next section
discusses basic masking of images and using objects as masks.
Creating a Key
Typically (and hopefully), footage to be keyed is shot on a blue or green screen. A
keying filter is used to remove the blue or green color from the footage. The areas of
the footage in which the color is removed become transparent, and the subject
remains intact. The footage is then composited over a background element.
The following keying example uses an easy-to-key image as a motion graphics element.
Keying in real life is rarely this simple. Since no keying filter automatically pulls a perfect
key, you must make adjustments to the filter parameters once it is applied. Also, you
must often use additional keying or matte filters, or use masks to remove portions of the
image the key does not remove. Sometimes other tricks are employed, such as color
correction and applied blurs. In this example, adjustments are made to the applied
Primatte RT filter parameters to create a cleaner key.
Note: Keep in mind that results vary greatly depending upon the images in your project.
This example merely provides an introduction to keying with the Primatte RT filter.
2505.book Page 149 Wednesday, June 30, 2004 5:58 PM