Apple Shake 4 - Manual (Page 430)

430 Chapter 15 Image Processing Basics
2 Connect the munch_mask node to the IDiv1 background input.
The edge appears clean.
3 To test the result, select the IDiv1 node and press I several times to ignore and show
the node.
By dividing by the mask, the image is unpremultiplied and ready for color correction.
Therefore, you can conclude that color correction should be applied to an
unpremultiplied image.
After going through all this, you may be surprised to find out that the insertion of IDiv1
and IMult3 can be bypassed entirely.
To bypass the insertion of IDiv1 and IMult3:
1 Delete the IDiv1 and IMult3 nodes.
2 Select the ContrastLum1 node, then press E to extract it from the tree.
3 Drag the ContrastLum1 node between the munch_unpremult node and the IMult1 node
to snap it back into the tree.
IDiv inserted IAdd1 detail