Time to refocus

I was visiting some friends at the weekend and took my camera with me. (Following last week’s blog post, of course!) The only lens I had with me was my trusty 50mm f1.2L lens. After a couple of frames, I noticed that the focus on the preview images looked a little soft. But it’s hard to be certain from the preview images as they are not high resolution anyway, and the screen on the 5D MkII is only a couple of inches across. So I used some of the furniture that was around to experiment and see if I could confirm my suspicions. Unlike when I’m shooting professionally, I didn’t have any spare kit with me.

I’ve read about autofocus test charts before, but never had cause to try one. I printed a chart from Jeffrey Friedl’s site and spent some time this evening testing the 50mm against my other lenses. What did I find? Well, the first photo below was taken using the 50mm at f2.8, ISO 100, 1/200th, no sharpening. The second was taken using 24-70mm at f2.8, 50mm, ISO 100, 1/200th, no sharpening. It seems pretty clear that the 50mm has developed a rearward focus bias.

Although the 5D MkII camera can retain individual autofocus adjustments, the lens also seemed to be lacking a clear focus field at higher apertures too. So I am going to send it off to Fixation UK who are a Canon authorised repair centre to get it sorted out! I’m pleased that I spotted the problem so quickly and was able to verify it satisfactorily. I love that lens, so will be glad to get it back home safely!

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    3 Responses to Time to refocus

    1. Pete Stean says:

      Good luck with it Tony – I think I have the same issue with my f1.4 50mm, but I might just trust to the in-camera focus adjustment for the moment. I dread sending it off anywhere…

    2. Tony says:

      Thanks Pete! It went off today, it was hard to say goodbye!

    3. Tony says:

      Well, I got it back. They said the lens was within Canon spec. Unfortunately the filter was smashed in transit but I sent it back and they retested the lens again and replaced the filter.

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