Canon EF 16-35 mm f/2.8L III USM
|Canon 50D, 16 mm, f/2.8||Canon 50D, 16 mm, f/4.0|
|Canon 50D, 24 mm, f/2.8||Canon 50D, 24 mm, f/4.0|
|Canon 50D, 35 mm, f/2.8||Canon 50D, 35 mm, f/4.0|
At 16 mm and f/2.8 the vignetting is noticeable even on the smaller sensor. We got a result of 33% (−1.18 EV). Fortunately for f/4.0 and f/5.6 apertures the problem becomes negligible with values of 13% (−0.42 EV) and 10% (−0.32 EV) respectively.
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At the 24 mm focal length you get a bit lower vignetting level because, with the lens wide open, the light fall-off in the frame corners reaches 28% (−0.94 EV). Once again the problems end by f/4.0 and f/5.6 where the aberration described here decreases to 10% (−0.31 EV) and 7% (−0.21 EV) respectively.
You experience the least problems at 35 mm where, by f/2.8, the vignetting is just 20% (−0.65 EV) and it goes down to 7% (−0.20 EV) after stopping down the aperture to f/4.0.
Now let’s check the situation on full frame – the appropriate thumbnails are presented below.
|Canon 5D III, 16 mm, f/2.8||Canon 5D III, 16 mm, f/4.0|
|Canon 5D III, 24 mm, f/2.8||Canon 5D III, 24 mm, f/4.0|
|Canon 5D III, 35 mm, f/2.8||Canon 5D III, 35 mm, f/4.0|
It would be difficult to call this situation other than dramatic. Such high vignetting we haven’t seen so far in our tests. At 16 mm and by f/2.8 in the frame corners disappears 75% of light (−4.07 EV). On stopping down the aperture to f/4.0 the situation improves but still the vignetting remains very high, reaching 57% (−2.47 EV). You can notice it without any problems by f/5.6 and f/8.0 where it is respectively 40% (−1.50 EV) and 32% (−1.10 EV). Even by f/11 and f/16 the problem remains noticeable (27% and −0.93 EV).
By the 24 mm focal length the situation is better but still far from good. By employing the maximum relative aperture you must take into account losing 58% of light in the frame corners (−2.52 EV). On stopping down the aperture to f/4.0 the vignetting decreases to 34% (−1.21 EV) and further stopping down to f/5.6 makes it drop to 23% (−0.77 EV). Only by f/8.0 and f/11 you can talk about a small level of that aberration, with results amounting to 17% (−0.52 EV) and 15% (−0.46 EV) respectively.
The least vignetting problems you can observe at the 35 mm focal length where, at the maximum relative aperture, that aberration reaches 45% (−1.17 EV), and at f/4.0 it decreases to 23% (−0.77 EV). The issues are practically over by f/5.6 where the vignetting value measured by us amounted to 10% (−0.32 EV).