Since I happen to have two 45mm lenses, I thought I would run an impromptu sharpness test in my back yard. I used a tripod, and both lenses had hoods on them. It was cloudy, so contrast and glare weren't problematic here. All shots were focused on the front tree trunk. These were OM-D raw files exported out of Lightroom 4.1 with no adjustments at all. First the native Olympus lens @ f/4.0: E-M5    OLYMPUS M.45mm F1.8    45mm    f/4.0    1/160s    ISO 200 Now the adapted Minolta lens @ f/4.0: E-M5    Minolta MD Rokkor-X 45mm f/2.0    45mm    f/4.0    1/160s    ISO 200 My focus might be a touch off, but I think the Olympus is better here. Now the native Olympus @ f/8.0: E-M5    OLYMPUS M.45mm F1.8    45mm    f/8.0    1/40s    ISO 200 And finally the adapted Minolta lens @ f/8.0: E-M5    Minolta MD Rokkor-X 45mm f/2.0    45mm    f/8.0    1/40s    ISO 200 I give the nod to the Minolta here, for sharpness. It seems that the Olympus has very slightly smoother bokeh and slightly less chromatic aberration, but it's really pixel peeping to find the difference IMHO. Even the differences in sharpness are very tough to spot. Very evenly matched IQ. The Oly is smaller and lighter and has auto-focus, but the Minolta costs about 1/8th as much. Pick your poison. I think the lens designs and intended platforms play into this - native micro-4/3 lenses seem to have diffraction problems above f/5.6-f/11 depending on the lens quality, and old 35mm camera lenses were probably designed to peak in the f/5.6-f/11 range.