Canon EF 70-200 mm f/4L IS II USM review - Coma, astigmatism and bokeh

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Canon EF 70-200 mm f/4L IS II USM

6 November 2019

Arkadiusz Olech

7. Coma, astigmatism and bokeh

The tested lens should be only praised for its coma correction. In the corner of the APS-C sensor its level remains imperceptible. Images of a diode, positioned at that place, don't differ from images you get in the frame centre. In the corner of full frame coma makes itself felt a bit at the shortest focal length - you can notice a slight deformation of the light point which turns into a comma. Still that effect is not very pronounced and it cannot change a very positive assessment of the lens in this category.

Here the Canon fares similarly well as the Nikkor and noticeably better than the Tamron. What's interesting, though, the Tokina managed to best all opponents – even in the corners of full frame images of the diode, produced by that lens, were almost deformation-free.

Center, 70 mm, f/4.0	Corner APS-C, 70 mm, f/4.0	Corner FF, 70 mm, f/4.0

Center, 135 mm, f/4.0	Corner APS-C, 135 mm, f/4.0	Corner FF, 135 mm, f/4.0

Center, 200 mm, f/4.0	Corner APS-C, 200 mm, f/4.0	Corner FF, 200 mm, f/4.0

Center, 280 mm, f/5.6	Corner APS-C, 280 mm, f/5.6	Corner FF, 280 mm, f/5.6

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When it comes to astigmatism you can be even more pleased than in the case of coma. The average difference between horizontal and vertical MTF50 function values amounted to just 1.9% and that's a sensational result. In this category the Nikkor 70-200 mm f/4 VR fared almost equally well (2.3%) and the Tamron and the Tokina were a tad worse (8% and 11% respectively).

It's worth adding that after attaching the teleconverter astigmatism increases but only to 3%. That result still can be called very good and we should praise the cooperation of the tested lens with the TC 1.4x III again.

When it comes to the appearance of blurry areas we don't have any reservations. Circles of light are nice to look at, without any distinct local extremes. Even the rim on the edge is not particularly accented. We are concerned a bit by mechanical vignetting which remains visible even by f/8.0 –for instance that effect was non-existend in the test of the Tamron 70-210 mm. On the other hand the Nikkor 70-200 mm f/4 VR showed even more truncated circles.

Center, 135 mm, f/4.0	Corner APS-C, 135 mm, f/4.0	Corner FF, 135 mm, f/4.0

Center, 135 mm, f/5.6	Corner APS-C, 135 mm, f/5.6	Corner FF, 135 mm, f/5.6

Center, 135 mm, f/8.0	Corner APS-C, 135 mm, f/8.0	Corner FF, 135 mm, f/8.0