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Lense Back Focus Issues!

  • 25-10-2007 10:07pm
    #1
    oshead
    Closed Accounts Posts: 2,131 ✭✭✭


    I was browsing the internet the other night and came across some people talking about the EOS 40D and back focusing problems. Since i'd just got a new 40D I decided to do a few tests with a couple of lenses. The EF 24-70mm f/2.8L USM and the EF-S 60mm f/2.8 Macro USM Lense. Here are the results...

    (Large file warning 3.5mb)
    EF 24-70mm f/2.8L

    EF-S 60mm f/2.8 Macro

    The EF-S 60mm image is obivously far superior in both sharpness, contrast and general image quality than the 24-70mm L. You can see how the 24-70 focused almost a full 10mm behind the focus point. Where as, the 60mm is tack sharp and right on focus.

    So as its turned out the 40D I own dosn't back focus. That I'm thankful for.

    My question is this...
    How do get the 24-70 fixed? Am I being too pedantic towards this lenses image quality? After all I paid up to €1000 for it. What would you do?

    If anyone else is interested in downloading the test chart, you can get it here

    Thanks
    Dave OS


Comments

  • #2
    Paulw
    Registered Users, Registered Users 2 Posts: 13,381 ✭✭✭✭Paulw


    Personally, I've never had a single focus issue with my 40D and my 24-70 f/2.8 L. It's the lens most used on the body.


  • #3
    mathias
    Closed Accounts Posts: 2,174 ✭✭✭mathias


    The 60mm prime is going to be better at focusing an also sharper than any zoom , or at least thats my experience anyway.

    Did you autofocus or manually focus with the zoom ? You may not actually have a problem here at all , zooms are not equal to primes , even L zooms , but of course the versatility of the zoom is the benefit. Its a kind of trade off.


  • #4
    oshead
    Closed Accounts Posts: 2,131 ✭✭✭oshead


    I tried both manual and Auto fous with the same results. I checked my EF 50mm 1.4 and its focus is bang on. Though no way near as good as the 60mm. The kit lense EF-S 18-55m back focuses by about 15mm and the EF 28-135mm IS front focuses by about 15mm. I was unable to do a proper test with my 70-200mm. The minimum focusing distance is too high. Though I'm happy with that lense. It's tack sharp for a zoom.

    I will do some more tests with the EOS 400D tonight to see if I get the same results.

    Dave OS


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