I have the 85 1.4 sigma and if its in your budget then Its a fantastic lens
It is my favourite portrait lens 9 circular aperture blades make for excellent bokeh and blur
I think I am ordering it tomorrow:) On the photozone.de page they write in the conclusion that: " The amount of bokeh fringing (LoCAs) is on the high side though so you may spot some colored out-of-focus halos in critical situations. ". Someone in here suggested that this might be solved by the use of a good UV filter. In your experience, would an expensive UV filter like one from B&W help with this? And finally, have you had any problem with this, and if so, is it an easy fix in photoshop? (I have the CS5 extended).
At 1.4 there is some purple fringing in contrasty light however in LR the lens correction clears it right up
and at f2 sharpness is outstanding (its sharper than the 70-200 II is at f2.
and CA is gone, I use this lens mostly at f2 unless I really want that razor thin DoF or am chasing crazy low light
at f2 this lens is outstanding.
My copy was heavily front focusing and I sent it back and had it recalibrated and now its perfect
my feeling is that wide open the canon f1.2L is unparalleled for sharpness and image quality however its focusing speed is ponderous when shot side by side with the sigma and its 2.5x more expensive bigger and heavier
I chose the sigma for the more snappy preformance mostly and its ability to be used more easily on the run and it's generally a better all round performer.
however if money is no object and you are going to be posing the models more of the time or shooting in controlled light where AF speed isnt an issue then the canon 85 f1.2L II cannot be beaten