Lens review
Canon EF 70-200mm f/4L IS USM
8. Vignetting
For the full frame Canon 70-200 f/4 IS we didn’t expect any problems with vignetting on the APS-C detector. We were right; the problem with vignetting was almost absent.
At the 70 mm focal length and open aperture the light fall-off in the
corners of the frame was only 9% (-0.27 value of the diaphragm) and
it is almost unnoticeable. After stopping down to f/5.6 the
vignetting decreases to 2%. We noticed the same situation at 135 mm.
At f/4 the light fall off reached 9% and after stopping down to f/5.6
it is 2%.
The vignetting is a bit visible at the 200 mm focal length. At the maximum aperture the result is 17% (-0.55 value of the diaphragm) but the defect disappears after stopping down the lens to f/5.6, where it reaches only 5%.
It is, again, worth adding that with 1-2% accuracy the vignetting values are the same as for the 70-200 mm f/4L non-stabilization version.
We also would like to mention the influence of the converter on the vignetting. As a result, after lengthening the effective focal length and maximum aperture drop off, the vignetting decreased to 10% (-0.3EV) at f/5.6 and then decreased to 1% at f/8.0.
