why can't you focus when zooming all the way in?

Discussion in 'Photography Beginners' Forum' started by ph0toe, Oct 31, 2019.

  1. ph0toe

    ph0toe TPF Noob!

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    using a zoom lens and zoom all the way to the maximum focal length say 105mm. why it won't focus in the viewfinder? but it will focus when i turn the zoom down to say 70 or 24mm?


     
  2. 480sparky

    480sparky Chief Free Electron Relocator Supporting Member

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    What lens?
     
  3. ph0toe

    ph0toe TPF Noob!

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    standard 24-105 canon L 1 series
     
  4. 480sparky

    480sparky Chief Free Electron Relocator Supporting Member

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    Are you close to the minimum focus? Perhaps when you zoom out, the camera's focus module can find enough contrast to focus, but at 105mm there isn't enough contrast.
     
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  5. Dacaur

    Dacaur TPF Noob!

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    That should not be the case. There may be a problem with your lense or camera.
     
  6. Destin

    Destin Been spending a lot of time on here!

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    This.

    Try putting the focus point over a high contrast area of the image. Also, at longer focal lengths your depth of field becomes thinner. This means that your camera may hunt for focus more, and if it’s already on a low contrast area then the this may just make it too hard to find focus.

    Its always possible that there’s a problem with your camera or lens, but that would be hard for us to diagnose without being able to examine it.
     
  7. Original katomi

    Original katomi No longer a newbie, moving up!

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    Have you tried using manual focus just to see if/that the lens will focus
    Eg rule out a least one fault
    Ok back just been looking at some reviews to remind myself.
    The mfd minimal focus distance is .45m
    You will have to look to see that you are not shifting the auto manual focus selector as you zoom,
    Finally for now
    There were some flare problems on some of those lenses that canon repaired model dependent.
    Personally for the cost of a phone call/e mail I would find the serial number of the lens and contact canon explaining the problem or if bought from a dealer /camera shop
    go back to them
    Info source should you want to look up is
    The digital picture dot com
    Look for the review of the lens
    Just looked at canon home uk,
    There was a problem with some of their early lens
    I am looking at the software manuals section the info on Effected lenses is there
    Hope this helps
     
    Last edited: Nov 1, 2019
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  8. wfooshee

    wfooshee No longer a newbie, moving up!

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    Isn't the minimum focus distance different at different focal lengths? That's actually something I would expect, and have seen myself. Short focus length and fairly close, with good focus, when I try to zoom in I'd be unable to focus.

    How close a subject are you trying to shoot?
     
  9. 480sparky

    480sparky Chief Free Electron Relocator Supporting Member

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    If it changes based on focal length, then it should be in the specs.... just like variable-aperture zooms.
     
  10. Solarflare

    Solarflare No longer a newbie, moving up!

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    It should always focus, unless you are too close and thus the lens is simply physically unable to focus.

    All zoom lenses I own have the same minimum focus distance, no matter what focal length you choose, but maybe that lens you have there is different ? After all, I dont have many zoom lenses and I havent used any of those I have in years by now.
     
  11. Original katomi

    Original katomi No longer a newbie, moving up!

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    Have you spoken to canon to see if your lens was one of the ones affected.
    Otherwise, take a tape and measure the distance that you are trying to focus at.
    Avg male stride is 3/4 of a meter which is about the min focusing distance for that lens.

    If you have one put a steel tape rule out with the camera on a tripod, with the end of the tape at the focal plane and take pics of the tape getting closer till it will not focus
    I can’t see if you replied did you try manually focusing the lens?
    Re specs, they can be found at canon home uk or your equivalent
     
  12. petrochemist

    petrochemist TPF junkie!

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    I DO have many zooms (over 80).
    Its pretty rare to find a zoom that does change MFD with focal length. I'm fairly sure the only ones of mine that do are those with jury rigged adapters (projector lenses etc). If adding extension of a macro supplementary MFD will be highly focal length dependent but this is not normal operation.
     

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