Resolution: Already excellent at f/2 the centre resolution increases to a peak at f/4. At f/4 and stopped down further corner resolution is extremely good

Chromatic aberration: Modest levels with macro use at f/8 which can be corrected with software. For non-macro use the lens have extremely low chromatic aberation (see Lens Lineup on this site)

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

Macro Sweet Spot: f/5.6 - f/8