Apple Shake 4 - Manual (Page 877)

Chapter 28 Filters 877
Grain Example
In the following example, the first node tree consists of a Ramp node and a PlotScanline
node. The PlotScanline node is added to analyze the image.
Because the ramp is black to white, a linear line appears in the plot scanline from left to
right when no grain is applied.
When a Grain node is inserted between the Ramp node and the PlotScanline node,
noise is introduced that disturbs the line. There is more noise (grain) near the lower,
dark area of the plot scanline. This is due to the filmResponse of -1, which concentrates
grain on the lower areas.