SUGGESTION: Take "Focal Distance" from C4D´s Camera "Focus Distance"
C4D Users are used to focus the scene by setting the C4D cameras Focus Plane.
You´ll find it under: C4D Camera, Attributes, Object, Focus Distance.
This can easily be linked to the Corona Camera Tag´s Focal Distance.
Also I have seen that there is a feature that allows Individual Maps to define the apperance of the Bokeh.
Would be really nice to see those in the Corona C4D Camera :-)
About the Focus Distance see Screenshot of C4D Camera attibutes