A canon lens service question

Discussion in 'Digital SLR' started by eatmorepies, Nov 3, 2010.

  1. eatmorepies

    eatmorepies Guest

    I have a Canon EF 300mm F4 L IS that is not as sharp as I think it should

    Reviews on the net suggest that this is one of Canon's sharpest lenses. I've
    had it 5 years (bought new) and have never been particularly impressed.

    I tried it on my 5D mkII and now my 1D mkIV - they needed +18 on the
    microfocus adjust control to get best sharpness from this lens. None of my
    other Canon lenses need adjustment on these bodies. The 300mm is certainly
    not as sharp as my 70-200 f4 L IS - the 300mm is argueably not as sharp as
    the 70-200 f4L IS when the 70-200 is combined with the 1.4x mkII multiplier.

    Anyone with experience of this 300mm L lens that can confirm the legendary
    sharpness? Might a Canon service restore this lens to the level of sharpness
    designed into it? Anyone with experience of Canon Service Centre lens


    eatmorepies, Nov 3, 2010
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  2. eatmorepies

    Bruce Guest

    The lens should be as sharp as a tack. It is one of Canon's finest
    lenses and should provide results that are superior to those from the
    f/2.8 version.

    A competent service technician should be able to diagnose and solve
    the problem. You should send your camera body/bodies with the lens so
    that they can be recalibrated together. I had a series of focusing
    problems with my 5D bodies and EF 24-105mm f/4 and 70-200mm L lenses
    which were only solved when camera bodies and lenses were recalibrated
    at the same time. From then on, I had no problems.

    One thing you could do now is check whether the lack of sharpness is
    due to the lens focusing at the wrong distance. I use a paling fence
    or iron railings (I live in the UK) and put a glove or some other item
    on one paling (or railing) then aim along the fence, focus on it and
    shoot. The result will show you whether the lens is focusing at the
    correct distance (glove) or a paling in front or behind. I do this
    with every lens I buy and it is surprising how many lenses are not
    properly calibrated.

    If the lens is focusing at the correct distance, the lack of sharpness
    will be caused by something else, such as decentering of one or more
    of the lens elements. This can be cured by a competent service

    In the UK I only ever use an independent service centre that is
    authorised by Canon UK to carry out warranty repairs. The reason is
    that the service centre has an outstanding reputation and I have long
    experience (10+ years) of their technicians - they are also authorised
    by Nikon UK. You may want to ask other Canon users in your country
    which is the best service centre to choose - Canon or an independent.

    Good luck!
    Bruce, Nov 3, 2010
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  3. eatmorepies

    eatmorepies Guest

    Thanks for confirming that the lens should be very sharp.
    I've done my version of this which is why I arrived at +18 on the microfocus
    Thanks for your reply. I'm now in contact with an authorised Canon Service
    Centre in Stoke on Trent (I'm also in the UK). I'll get them to make the
    necessary adjustments.

    eatmorepies, Nov 3, 2010
  4. eatmorepies

    Bruce Guest

    I strongly recommend Fixation in London:

    Bruce, Nov 3, 2010
  5. Most probably your body is miscalibrated and most of your lenses
    are fine --- ever thought of that?

    Wolfgang Weisselberg, Nov 4, 2010
  6. eatmorepies

    Bruce Guest

    If only you had read my contributions to this thread rather than
    snipping a tiny morsel from one of them and replying to it out of
    context, you would already know the answer to that question.

    Instead, you wasted your time.
    Bruce, Nov 4, 2010
  7. I read the rest. Do I need to quote it instead of reading it?
    You never thought of that. You didn't think things through ---
    maybe because of mental lazyness, maybe because you never had
    the relevant information.

    You had a lens and a body calibrated *together*. Fine. Doesn't
    say a thing. Both may be miscalibrated, but in a way that they
    are a good match for each other.

    Every thinking being knows that being calibrated is 'being in an
    acceptable range' not 'perfectly to the point'. Most probably
    both your lens and your single are both at the edge of the
    tolerance band of being calibrated.
    Talking to you ist wasting time, indeed, I better killfile you
    again so I won't be tempted to add wisdom to your words.

    I am not talking to you, I don't want to 'waste' your time, I want
    you to send back lens after lens after lens for misfocussing and
    loose time that way --- a calibrated lens and a calibrated body
    may still combine into a sub-perfect ensemble. And if you find
    that many lenses are 'not properly calibrated' --- a claim which
    you simply cannot prove, not having the necessyry gear nor the
    information which band of alignments are within specifications as
    defined by the maker --- i.e. if you find that many lenses do not
    pair well with your single camera, then it is quite obvious that
    your single body (or two bodies) may be at fault, not the myriad
    of lenses. But you, like the guy driving on the wrong side of the
    lane, think everyone else is at fault and needs to be corrected.


    PS: https://www.lensrentals.com/news/2008.12.22/this-lens-is-soft-and-other-myths

    Their numbers --- and they have tons of lenses --- don't
    support Bruce's "many lenses". And that bodies may be at
    fault, being at the edge of tolerance.


    And here is some more information, including more points how
    bodies can be less than perfect and thus let the majority
    of the lenses seem bad, especially in a certain way.
    Wolfgang Weisselberg, Nov 5, 2010
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