Resolution: Already excellent at f/2 the centre resolution increases to a peak at f/4.

Chromatic aberration: High fully open but significantly lower when stopped down. For non-macro use this lens has extremely low chromatic aberation (see Lens Lineup on this site). Chromatic aberration is not significant on a DX sensor.

Vignetting: High at f/2 but moderate when stopped down to f/5.6

Macro Sweet Spot: f/5.6 - f/8