Quote - Now... about that "visible aberation" that EnglishBob mentioned...

I've been thinking about that. You don't mind me taking over your project, do you? :D

Chromatic aberration occurs because different colours are refracted by different amounts - so maybe you could fake it by doing three renders, one each for the R, G and B components of the lights used (i.e. turn the other two down to zero). Vary the IOR of your lens for each render, then re-combine. Only the light that's passed through the lens should be different, so the rest of the scene should recombine; if not, then a full-colour rendering will be required along with a little more compositing.