Apple Shake 4 - Manual (Page 862)

862 Chapter 28 Filters
The result—is merely a blend between sharp and blurred elements—is not very
compelling. (Note that the Ramp node has a default alpha value of 1 for both ends; you
should change the alpha1 value to 0.)
To get a better result, use the dedicated IBlur node instead, with the Ramp node as the
second input image, rather than a mask input.
Filters Within Transform Nodes
Filter operations aren’t limited simply to blurs, emboss effects, and other convolution
operations assigned to filter nodes. Filter parameters are also available in many
transform nodes.
Most filter and transform nodes allow you to use one of many different filtering
processes to perform transforms, blurs, and convolve effects. Which filter you choose
can make a big difference in the quality of the resulting effect, especially when
animated.
To maximize the quality of scaling in Shake, the “default” filter setting in transform
nodes actually switches between two different filters—the mitchell filter for nodes that
increase image scale, and the sinc filter for nodes that decrease image scale. A panel of
film professionals watched several versions of a shot that had been processed with
different filters projected onto a cinema screen. They decided that the mitchell and sinc
filters provided the best quality. Other filters, such as the box filter (the closest
operation to what is more commonly referred to as “bilinear”), may give subjectively
superior results in some cases (particularly with static images) but tend to handle high-
frequency image data poorly.