Canon EF 135 mm f/2L USM review - Autofocus

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Canon EF 135 mm f/2L USM

3 October 2011

Arkadiusz Olech

10. Autofocus

The tested lens is equipped with an ultrasonic USM motor so its work is practically noiseless. What’s more, it is also fast. Running through the whole distance scale takes about 0.7 of a second and, after limiting the focus to the range from 1.6 m to infinity that time is shortened to about 0.3-0.4 of a second. These results are really good.

The accuracy of the mechanism is beyond reproach. The lens offers shallow depth of field so any misfocus would be clearly visible. These seldom happened, though because in studio conditions their number didn’t exceeded 3%.

When cooperating with the EOS 1Ds MkIII the lens didn’t show any front or back focus tendencies. The situation changed when we attached it to the EOS 50D camera, on which the lens had a pronounced back focus. We managed to calibrate it by using the autofocus microcallibration function, available in the menu. After that the lens focused correctly where it should.

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