Sigma 28-70 f2.8 DG
The lens i tested was in Nikon 'D' mount. This was the first version of this DG lens which boasted better multicoating for use with digital cameras. It is a full frame lens, though. I found the sharpness from 28mm-35mm to be very good at all apertures. However, at 50mm - 70mm the sharpness is excellent from f4 up. At 50mm f5.6, it is quite sharp. Contrast is average at all focal lengths, but slightly soft at 70mm. Color rendition is neutral. Fringing was not apparent though I didn't fully test that yet. I assume it is well controlled because of the advanced coatings on this lens, though. I would rate this a pro-sumer lens. It is capable of excellent results. Shadow detail is excellent. This lens will be excellent for portraits with its sweet spot between 50mm-70mm at f4-f5.6. Image quality on a Nikon body should be better than what I can produce on a Canon body with an adapter.
ISO 200 - 28mm - f5.6 - 100%crop
ISO 200 - 70mm - f5.6 - 100%crop