Using an ID pass, to isolate a CGI element within the scene, to create a blur and colour adjustments, to just that particular area.
In this case the tree bark. The render was too sharp, so I adjusted the ranges, just on the rgb_red channel (the tree geometry had a red surface shader applied to it in Maya prior to render)
Image Below:
ID pass adjustments. Red rectangles highlight the ID pass in the node graph, the final image in the render view and the range and rgb channel selector on the right.
Bark with the blur node deactivated. Bark looks sharp
Blur node on bark activated
Connecting the ID pass to the colour correct node, so that the individual R G B channels can be selected
