Color Correction - Nuke 101: Professional Compositing and Visual Effects - page 176

The resulting image looks exactly as before ( Figure 4.26 ). This technique does
exactly the same thing as the first method, just without using other nodes. I usu-
ally prefer the first method as it shows clearly in the DAG that the premultiplica-
tionissuesarehandled.However,ifyoulookatGrade1intheDAGnow,youwill
see that, although a smaller indication, Grade1 is showing that it is dividing the
RGB channels with the alpha channel. The label now says “rgb/alpha” ( FIGURE
4.28 ) .
Figure 4.28. The node's label changes to show the Unpremult and Premult
operations are happening inside the node.
Let's use the second method you have set up already. You will now be color cor-
recting an unpremultiplied image, but outputting a premultiplied image. After a
little rearranging, the tree should look like that in FIGURE 4.29 .
Figure 4.29. Your tree should look like this at this point.