Lens review

Canon EF 100-400 mm f/4.5-5.6 L IS USM

8. Vignetting

On a small Canon 20D sensor we didn’t expect any problems with vignetting and we were right – this problem won’t be a bother almost at all while working with the Canon 100-400 mm.

At 100 mm and wide open the brightness loss in the frame corners amounts to just 10% (-0.31 EV) and on stopping down by less than one stop, to f/5.6, it decreases to 5%. In both cases, then, the aberration is simply imperceptible.

The performance is even better at 200 mm where, by f/5.0, the vignetting reaches 8% (-0.24 EV) and by f/5.6 – only 4%.

At 300 mm and by f/5.6 we notice once again no problems whatsoever because the light fall off is just 10% and decreases to 2% on stopping down by one stop.

Only at 400 mm we have any chances of perceiving any vignetting. At the maximum relative aperture it amounts to 15% (-0.46 EV) and it decreases to 5% by f/8.0.