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    AF Micro-adjustment

    I'm intrigued by this function. As I understand, it can only be used in AF mode, and with Canon lenses. (Obviously in MF, you do the focusing, so AF micro-adjustment doesn't apply).

    From what I read from canon - being the most reliable source of information - it is generally not needed. Only if the camera/lens suffers a drop etc...

    So, why then on these forums - if you do a google search on this theme, lots of results come up referring to photo forums- that loads of people have to calibrate their expensive camera and L lenses because their L lens either front focuses or back focuses and hence needs to be calibrated!! To me, this doesn't make sense. As far as I can tell, my lenses are fine - and I don't own L lenses. Does this mean, that cheaper lenses i.e. Sigma are better at focusing?

    I think that because we have this function, it is a good selling point for Canon - we can calibrate our own lenses.
    But I also think it has created another problem because nowadays we are obsessed with sharpness - hence HD TV, lenses being clearer/sharper than crystal!! So unhappy customers still send back their perfectly calibrated camera/lens as being unsatisfactory! As digital technology increases, we are getting more and more obsessed with things that make little difference in real life.

    The old motto; 'If it ain't broke, don't fix it'

    Thesedays we are fixing things that ain't broke!

    What do other members think about this?

    I'm intrigued!

    Do other members have problems with their L lenses and Canon lenses in general so much so that the micro-adjustment has to be used? If so, what are your adjustment measurements?

    I will also add that I think once again sharpness and focus is subjective. I think the micro-adjustment focus can be compared to sharpness as seen through the USM in Photoshop. What is sharp/infocus for one person is unsharp/out of focus for another!!
    Richard

    Think before you press the shutter button!

    #2
    Re: AF Micro-adjustment

    Colin C wrote up an easy way of checking. NorthLight published this http://www.northlight-images.co.uk/a...djustment.html (works with the 7D).

    I had a play ... and my set up was okay in the end. It's easy enough to 'undo' the correction.

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      #3
      Re: AF Micro-adjustment

      In any manufacturing process there are tolerances.

      Cameras and Lenses are no different.

      When a camera auto focuses it will be to a given tolerance (i.e within the visible range of what the eyes can perceive as being in focus) and when the lens adjusts its focus at the command of the camera, the movement of the components will also be to a tolerance.

      Usually the result will fall somewhere in between the tolerances of both the camera and the lens and produce an image which is as in focus as is needed to be perceived as in focus by the human eye.

      But, if you happen to have a camera which is bias towards one end of the tolerance range, and a lens which is bias towards the other end of the tolerance range, then the resulting image may appear soft to the human eye.

      This is why sometimes people will have a lens which on a particular camera body produces very sharp images but when they upgrade the camera body, the same lens seems to produce an image which is noticeably softer than it was before.

      This is where the AF Micro-adjustment becomes useful.

      It' not an issue with Canon kit, it's just the nature of any manufacturing process; nothing can be made infinitely perfect.

      Comment


        #4
        Re: AF Micro-adjustment

        Very well put Skonk.

        Though for anyone overly concerned, it generally isn't a problem for the majority of cameras and lenses. If you are using fast telephoto lenses wide open, it is worth checking whether they are focussing accurately and also very fast lenses such as the 50mm f1.2 and the 80mm f1.2.

        Colin
        Colin

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