Apple Shake 4 - Manual (Page 888)

888 Chapter 28 Filters
Sharpen
Un-sharp masking is used for the sharpening filter. This process blurs the image slightly,
takes the difference between the blurred result and the input image, and adds that
back over the input image. High values of x and yPixels (for example, greater than 3
percent of the image size) return undesirable results. You can also use the sharpen filter
in the Convolve node, but ringing may result.
Parameters
This node displays the following controls in the Parameters tab:
percent
The amount of mixing between the sharpened and the original image. With a value of
100, none of the original image is present.
xPixels, yPixels
The amount of sharpening as described in pixels.
channels
The channels of the input image to sharpen.
ZBlur
The ZBlur node is a dedicated version of IBlur used to simulate depth-of-field blurring
based on the Z channel. You can set a center point of focus (focusCenter) and the
range of drop-off to the maximum amount of blur. If you do not have a Z channel, you
can copy a channel from another image. Therefore, if you are working in 8 bit or 16 bit,
your ranges are between 0 and 1. For example, your focusCenter could not be set to 10,
but is somewhere between 0 and 1.
The ZBlur node works best with gradual changes of Z, for example, looking down a
hallway, represented in the following images.
In cases where foreground objects overlap blurred background objects, ringing results
on the background. It is recommended that you separate the foreground from the
background into two separate elements. For example, do two renders if you are
generating elements in 3D.