Canon 85-300 f4.5 - Infinity Focus

Discussion in 'Canon FD' started by strappy, May 13, 1999.

  1. I've noticed when using this lens that it focuses to infinity (at 300mm) when the barrel markings indicate a distance of around 30m. When I turn the barrel to the infinity mark it goes out of focus again.

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    Is this common with this lens (or any longer focal length lens) or is there something wrong with my example?

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    Thanks in advance.
    Dean.
     
  2. Dean,
    No, this is pretty much normal - especially for telephoto lenses.
    Typically they are adjusted to focus "beyond" infinity at normal room
    temperture. When the lens is use on a hot sunny day, it will expand
    and will likely focus to infinity at the infinity mark.

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    Karl
     
  3. This is especially true of the L Series lenses. The low dispersion
    and spherical elements expand and contract at a different rate than
    the other lens elements. Thus some play to make sure you can always
    focus to infinity.
     
  4. Thanks for those replies. I've tried leaving the lens standing in
    the sun for a day to check this out (!) and the infinity focus point
    definitely moves.

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    BTW, the shots taken using the lens are fine!

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    Thanks,
    Dean.
     

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