I've been struggling with cutting between RPP and CP2 ... and I think you hit the nail on the head with the bokeh. I believe the RPP is 7 blades and the CP2 is 14 blades, and with shallow depth of field with a T setting of around 4 ... the bokeh difference is catching my eye (but in a way I can't give a "scientific" value to). At T1.8 the blade value goes to infinite on the RPP, giving nice round bokeh as the blades completely retract into a circular aperture thingy - so I find myself shooting at T1.8 using ND filters most of the time now.



