Sony "Carl Zeiss" 16-35 f/2.8
Minolta 24-105 f/3.5-4.5
Sigma 12-24mm f/4.5-5.6 EX.
24mm corner crops:
f-stop | Sony CZ 16-35 | Minolta 24-105 | Sigma 12-24 |
f/2.8 |  | ||
f/4 |  |  | |
f/5.6 |  |  |  |
f/8 |  |  |  |
f/11 |  |  |  |
Here the CZ and the Minolta give identical results at f/11, but the Sigma is definitely below the other two, although we can probably only tell the difference because the magnification is so high. f/8 is still usable, but anything below that and the performance is visibly degraded for the Minolta and Sigma. At f/4, the Minolta performance is so poor that it actually shows on the small pictures above.
The CZ is still ok at f/5.6, but f/4 and f/2.8 are quite poor. In truth, however, this is rarely important: only the extreme-extreme corners are affected (the top right of the picture is noticeably sharper than the bottom left) and this is not likely to show in actual use, where the corners will be dark (for night scenes) or outside of the depth of field.
Lateral chromatic aberration ("purple fringing") is visible in the 3 lenses (look at the tree trunk). This sort of aberration does not go away when one stops down and is very difficult to suppress for ultrawide. The CZ is not better than the other two in this respect.
The Minolta 24-105 confirms its use as an ideal travel lens, provided you stop it at f/8 or f/11.
Next: 28mm. CZ, Minolta 24-105 and Minolta 28mm f/2.0 prime.
