Hi!
***I am curious how to develop a Radiance-based post-process from
this polynomial function to arrive at a script that will take a HDR
image and apply a vignette correction.
All you have to do is to multiply your pixel values by your f(x) with x being the radius to the center. This can be done just using pcomb. Make sure to include the -o switch to eliminate any display settings (exposure etc).
Be aware that "center" is the optical axis and not necessarily the center of the sensor, so you must find out the pixel position of it.
Cheers
Lars.