Sony "Carl Zeiss" 16-35 f/2.8
Minolta 24-105 f/3.5-4.5
Minolta 28mm f/2.0 prime.
Here the corner pictures:
f-stop | Sony CZ 16-35 | Minolta 24-105 | Minolta 28mm f/2.0 |
f/2.0 |  | ||
f/2.8 |  |  | |
f/4 |  |  |  |
f/5.6 |  |  |  |
f/8 |  |  |  |
f/11 |  |  |  |
Quite interesting, isn't it?
The CZ confirms its superb quality. The lack of corner sharpness that we noticed at 16, 20 and even 24 mm is less of a problem, it decreases when zooming in. This is typical of wide-angle zooms (and in this respect, the Sigma 12-24 is atypical).
The Minolta 24-105 is surprisingly good, even if the full aperture (f/4) is not perfect, f/5.6 is quite usable and f/8 just as good as the CZ.
The 28mm prime is the worse of the three: corner shading is enormous and corners are never really sharp. Other tests showed that the reason is field curvature. That makes this lens totally unsuited to landscape photography for example (quite the contrary of the 20mm prime). Does this mean it is a bad lens? No, it only makes it an imperfect lens, but is has other advantages when used as it was intended, i.e. for available light photography. See next post.
