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  • #16
    Re: EC 20-2x

    Originally posted by Tordan58 View Post

    Regarding Cathrine's comment: F7.1 on this combo should be wide open if I got the maths right.
    Yes, without checking I think you're right. But I've never had such sharpness using the EC20. I think Greytop may be right, that there are pairs that work well and others that don't. Which isn't too convincing of the quality assurance system, though.
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    Cathrine

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    • #17
      Re: EC 20-2x

      Originally posted by benvendetta View Post
      There is a limit to the amount of stopping down you can actually do with this combo. I have determined that f9 is the optimum aperture. Any smaller then your shutter speeds and/or ISO are going to be compromised
      You will also start to see diffraction softening at f/9, although slight.

      Ian
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      • #18
        Re: EC 20-2x

        Originally posted by Tordan58 View Post
        I am surprised with the sharpness in the pictures shared by Huw, these have better detail rendering than the results I have obtained with my 50-200 SWD + EC20. Did you use MF, Huw?

        Regarding Cathrine's comment: F7.1 on this combo should be wide open if I got the maths right.
        Hello Tord, all images were autofocus with the E-5, the Moon image was manual focus with the E-M5.
        Wide open at 400mm is f/7
        Regards Huw


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        • #19
          Re: EC 20-2x

          Hi Huw,

          Thanks for info regarding focus method. It could be that the E5 is superior in AF performance compared to the E620 that I am using. It could also be that the 50-200 + EC20 that I use are poorly matched to each other (toleranses?). And lastly I know there is nothing wrong with my EC20 per se since I have achieved good results with two lenses that call for MF: OM 50mm F/1.4 and Skywatcher 600mm F/7.5 scope. I have yet to try the 50mm F/2, currently out on loan.

          /Tord

          PS Regarding my comment on wide open - what I meant is that F/7.1 (looking at the picture EXIF) was wide open. I should have written "very close to" since the theoretical value should be 7.0. My 50-200 @200, F/3.5 + EC20 displays a value of F/7.1 in the viewfinder/EXIF. Never mind...

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          • #20
            Re: EC 20-2x

            No worries Tord
            Regards Huw


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            • #21
              Re: EC 20-2x

              I've found sample variation in the OM system TC's. I have 2 OM 2x-A and after a while noticed one was better than the other. However I don't know which is currently in my Pelican and which is in the storage cabinet. I also have 2 OM 1.4x-A TC's but have never compared them.
              It's the image that's important, not the tools used to make it.

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