Lens review

Canon EF 28-135 mm f/3.5-5.6 IS USM

8. Vignetting

In this category the Canon, again, is taking advantage of its full frame design. However, the advantages are not that great since even using an APS-C the vignetting is clearly visible. The light fall off in the corners of the frame is the most problematic at 28 mm, with the open aperture reaching 24% (-0.79 the value of the diaphragm). Stopping down the lens to f/4.0 decreases the effect to 17% and then, while stopping it down some more, to an acceptable level of 10%.

At the 50 mm focal length range and an open aperture of f/4.5 we noticed the 19% light fall off in the corners (-0.61 the value of the diaphragm). When we use the f/5.6 diaphragm we reduce the vignetting to the 8% level.

The situation is even better at the 85 mm focal length. At f/5.6 the light fall off values reach 15% (-048 the value of the diaphragm). When stopping the lens one value down, the problem decreases to 6%. The situation is almost the same at the 135 mm focal length. The vignetting at f/5.6 and f/8 reach is, respectively, 14% and 6%.

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In summary, the vignetting is not a problem at the 50 to 135 mm focal length ranges. We can encounter a slight difficulty at 28 mm and with an open aperture, which is kind of an unpleasant surprise. We expected vignetting of less than 20% from a lens designed for a full frame.