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Focussing using an Extension Tube - HELP

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    #1

    Focussing using an Extension Tube - HELP

    Canon 50D with EF-S 17-85 lens.
    To do some close up photography I recently purchased a Canon EF25 II Extension Tube to use in conjunction with the above.
    However, when it is mounted with the lens I cannot achieve focus on anything, at any distance, at any focal length !!
    I have tried focussing Manually, as well as AF ( and even switched off Image Stabilization in desperation).
    I'm sure the lens and extension tube are correctly mounted.
    AM I MISSING SOMETHING HERE ?
    Any advice would be appreciated as I'm tearing out what little hair I have left over this.
    Thanks
    Tags: close up, extension tube, focus
    #2
    Re: Focussing using an Extension Tube - HELP

    Its been a long time since I used an extension tube....If my memory serves me right all I did was move nearer or further away from the subject...but this was before auto focus.
    When I fitted it to a zoom i just zoomed in and out til it was in focus.Someone out there will soon come and answer your question...im looking forward to the answer myself.

    Coda
    There will be times when you will be in the field without a camera. And, you will see the most glorious sunset or the most beautiful scene that you have ever witnessed. Don't be bitter because you can't record it. Sit down, drink it in, and enjoy it for what it is!

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      #3
      Re: Focussing using an Extension Tube - HELP

      I have a set of Jessops tubes but they have not been used much as i could never get on with them. As i have a 17-85 I tried a tube on it with my 40D and could not get it to focus either - not much help I'm afraid

      Stan
      Stan - LRPS, CPAGB, BPE2*

      http://neptuno-photography.foliopic.com/
      flickr

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        #4
        Re: Focussing using an Extension Tube - HELP

        The EF25 II is quite a big magnification and better suited to telephoto's, but I have just tried it on my 24 - 70mm with the following results:

        * It won't focus on anything at, or below 28mm, because the subject is touching the front of the lens.

        * At 50mm, there is a distance of 50mm between the lens and the subject and it focusss well.

        * At 70mm, there is a distance 0f around 150mm betwwn the lens and the subject and it focusses well.

        I never use auto focus or IS for macro, just manual focus, but I did try auto. It wouldn't "lock on" until it was reasonably near focussed. This is quite understandable, because the auto system needs contrast to focus and with the pronounced blur at macro, there isn't any contrast until you are focussed, or nearly focussed.

        Try it at 85mm with the lens on manual, pre focussed at infinity. Move towards your subject slowly from around 300mm away until it comes into focus (probably around 200mm away). Then rock slowly backwards and forwards until you have good focus to take the shot.

        Alternatively, go through the above on a tripod to get the focus as best you can, then switch on "Live View" and use the 5X, or 10X magnification to fine tune the focussing.

        Hope that helped.

        Colin
        Colin

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          #5
          Re: Focussing using an Extension Tube - HELP

          Yes, sound advice from coda and colin c above. Out of interest I dug out a EFS 18-55 and tried my EF12 Canon extension tube with it.
          At the "18 end" I had to take the lens cap off and even then the subject was more or less touching the front of the lens - makes it hard to get any light in!! At the "55 end" things were OK.
          I would suggest that you use the zoom function to get the "size" of image you are seeking and then move the camera/lens to get focus.
          Tend to keep the EF12 tube in the holster case to get a bit more "macro pull" with the 24-105 when I'm travelling light and don't have the 100mm macro with me. So saying, that tube works well with that lens because of its focal length.
          Cheers, Chris.
          Just chuggin' along.

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            #6
            Re: Focussing using an Extension Tube - HELP

            Originally posted by Chris J View Post
            Tend to keep the EF12 tube in the holster case to get a bit more "macro pull" with the 24-105 when I'm travelling light and don't have the 100mm macro with me. So saying, that tube works well with that lens because of its focal length.
            Some good advice in this thread and I'm sure the OP will have been helped by it all.
            Chris, which body do you use the EF12 / 24-105 combination on please ? I just wonder whether that might help me when 'travelling light', with 50D / 24-105.
            Thanks, Alan.

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              #7
              Re: Focussing using an Extension Tube - HELP

              Hi, Allcahie - I currently use a 50D, but sometimes revive a 20D or even the old 300D. if I'm going out with macro in mind I take the 100mm EF Macro lens - excellent thing - but when out strolling or not with any particular shooting in mind I take the 12mm tube in a soft pouch in the bottom of a Lowepro Cirrus TLZ25 where it sits safely until I want to get a bit closer to things than the 24-105 usually allows. I find that combination of tube and lens very good.
              Cheers, Chris.
              Just chuggin' along.

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                #8
                Re: Focussing using an Extension Tube - HELP

                Thanks Chris,
                I might just give it a try.
                Alan.

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                  #9
                  Re: Focussing using an Extension Tube - HELP

                  Many thanks to Colin C and all for your replies. I have now had limited success focussing around the max focal length of the lens (85mm) but exposure is tricky because the lens to subject distance is so small. Manual focussing appears to be a must though. Will also follow the advice to experiment with a larger zoom but I'd previously read that the these tubes were better suited to shorter focal lengths !
                  Thanks again.

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