Apple MA434Z/A User Manual - Page 681

Keying 24 24 Shake provides powerful, industry-standard keying tools in the Primatte and Keylight nodes, along with additional keying nodes such as LumaKey and SpillSuppress. When combined with Shake's other filtering, masking, and color-correction nodes, you have detailed control over every aspect of the keying process. About Keying and Spill Suppression The first part of this chapter presents different strategies for pulling keys in Shake. Keying can be loosely defined as the creation of a new alpha channel based upon the pixel color (a pure blue pixel, for example), luminance (a very dark pixel), or Z depth (a pixel 300 Z units away, for example) in an image. Keying is discussed as a separate process from masking, which can be loosely defined as the creation of an alpha channel by hand through the use of painting, rotoshapes, or imported alpha masks from 2D or 3D renders in other software packages. For more information on these masking techniques, see Chapter 19, "Using Masks." If you are not familiar with Primatte and Keylight (Shake's primary bundled keyers), you are encouraged to work through the keying lessons in the Shake 4 Tutorials book prior to reading through this chapter. 32-bit Support in Primatte and Keylight As of Shake 4, the Primatte and Keylight nodes preserve 32-bit image data. 681