Graphics Reference
In-Depth Information
The solution to this problem is to adjust the color channels directly and to bring down the level of green in
the image overall.
Tweaking Color Channels
To tweak the individual R, G, B, and A channels of an image directly, use a Separate RGBA Converter node,
described previously, to split up the values, and then use another Converter node, Combine RGBA, to put the
values back together as a completed color image.
In this case, you need to bring down the overall green level. However, there is a danger to bringing the level
too low. Remember, the character is holding a green object. Adjusting the green channel affects the color of
green things disproportionately, so an adjustment that might not make the image as a whole look unnatural may
easily alter the color of the doll so that it no longer looks green. There must remain enough energy in the green
channel that this object still looks green.
There's no single right answer to how to do this, but a simple solution is to average the energy levels of all
three channels and to use this average as the green channel. This significantly reduces the strength of the green
channel but ensures that the green channel remains stronger than the other two channels in places that are pre-
dominantly green to begin with. This can be done by using two Math nodes set to Add and one Math node set
to Divide, as shown in
Figure 9-74
. You can create math nodes by pressing Shift+A and choosing Converter >
Math from the Add menu. Collecting those nodes in a single node group and connecting the red and blue chan-
nels straight through yields the node setup shown in
Figure 9-75
. The difference between the image before and
after adjusting the green channel can be seen in
Figure 9-76
,
also repeated in the color insert of the topic.
