Canon EF 100 mm f/2.8 L Macro IS USM review - Autofocus

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Canon EF 100 mm f/2.8 L Macro IS USM

27 November 2009

Arkadiusz Olech

10. Autofocus

As we deal here with an L series lens, equipped with an USM motor our expectations concerning the autofocus work are high, especially that we put the lens on the EOS 1 Ds MkIII first.

Let’s start with a remark that, as it befits a good macro lens, we’ll find the focus distance limiter on its barrel . We can choose from three options: a 0.3m to 0.5m range, a 0.5m to infinity range and a 0.3 to infinity range. In the case of the latter, going through the whole distance scale takes about one second. On the one hand the lens is not exactly a speed demon on the other hand the range is very wide indeed. If you care about fast work you should use the limiter. After choosing the work mode for greater distances the autofocus increases its speed almost twice.

On the EOS 20D the lens operates with the same quickness and as silently as before. A two digit body autofocus is worse though because the mechanism gets lost more easily and it goes through the whole scale looking for the right setting more often.

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How does the lens fare when it comes to the autofocus accuracy? On the 1Ds there’s really nothing to complain about. The lens didn’t miss one single time during the studio shots! On the EOS 20D it fared a bit worse, though – the number of misses reached 3%. It is still a very good result. What’s interesting the 100L autofocus work is so good that an exchange from 20D to 50D won’t improve it significantly – on the 50D the number of misses is again about 3%. Such a result must be assessed as very good once again so the tested lens’s focusing mechanism we find beyond reproach.

The EOS 20D doesn’t have any possibility to calibrate front or back focus but that particular option proved to be redundant here – the lens didn’t show any front or back focus tendencies, either on the 50D or on the 1Ds MkIII.