Apple Shake 4 - Manual (Page 408)

408 Chapter 15 Image Processing Basics
Note: You must be careful when pulling a bluescreen matte with the ChromaKey
node. The outside black pixels are considered invisible because the node is keying a
non-black color.
To disable the effect of the Infinite Workspace, insert a Crop node and don’t modify its
default values (which does not change the resolution). This cuts off the area outside of
the frame, replacing it with black pixels. The Viewport node is similar to Crop, but it does
not disable the Infinite Workspace.
Note: Be very careful when scaling elements up, applying an operation, then scaling
back down. When you apply an operation to the scaled element, even though your
frame is small, Shake will calculate everything outside of the frame when you scale the
image back down to fit in the frame.
For more information on the Infinite Workspace, see “ Color Correction and the Infinite
Workspace ” on page 617. You can also see “ The Domain of Definition (DOD) ” on
page 82.
Bit Depth
Bit depth describes how many values are used to describe the range of colors in an
image. The number of steps in a range of color is calculated by taking 2 to the nth
power, where n represents the number of bits. For example, a 1-bit image gives you
two values—black and white. A 2-bit image gives you 2
2 , or 4 color values per channel.
Bit depth directly affects image quality in several ways.
Comparing Different Bit Depths
Higher bit depths allow you to more realistically represent a wider range of color, by
ensuring that the gradients between similar colors are smooth. Using a bit depth that’s
too low results in what is sometimes described as color banding—where, for example,
you can actually see the limited number of colors in between two shades of blue.
For a better understanding of how this happens, you can look at how a range of color
is represented at varying bit depths on a graph. In a simplification, the following charts
display a grayscale ramp in 1-bit, 2-bit, 3-bit, and 8-bit depths.