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Re: [PanoToolsNG] Samyang 8mm

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  • Roger D. Williams
    ... You re welcome. Hmmm. Looks a bit soft for F/5.6. Try it at F/8 and 11 and see if you get noticeable improvements. Also try 2.0m or even 3.0m. As I said, I
    Message 1 of 62 , Nov 1, 2010
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      On Mon, 01 Nov 2010 22:00:36 +0900, A Kielcz <roblee007@...> wrote:

      > Thank you Roger.
      > It was shot in RAW at 5.6 and focus was set to 1.5m.. I could not u/l
      > original NEF, because it wouldn't accept it.
      > Is it possible that CA wasn't even on both sides, because it wasn't
      > level?
      > Tests are good, but I want be able to correct anything anyway.

      You're welcome. Hmmm. Looks a bit soft for F/5.6. Try it at F/8 and 11
      and see if you get noticeable improvements. Also try 2.0m or even 3.0m.
      As I said, I had to focus further out than dictated by the hyperfocal
      rule in order to get the best sharpness from my Peleng.

      If CA is not the same on both sides the cause will be in the internal
      geometry of the lens, not any orientation of the camera. I suggested
      "decentering" which simply means that the optical axis of the lens
      isn't precisely aligned with the lens barrel. But the effect is very
      slight, so I wouldn't worry about it.

      You must have used a RAW file processor to get your JPEGs, and it
      can introduce softness in the resulting images. The RAW processor is
      where you should remove the CA. CA looks bad and seems serious, and
      if left uncorrected plays havoc with control point location (think
      about having fringes on the opposite sides of the same feature when
      it appears on the extreme left of one shot and the extreme right of
      the next, overlapping, shot! You don't want that. All RAW processors
      I've played with have sliders to eliminate CA. Play with them until
      you can't see coloured fringes at full x1 screen magnification!

      Roger W.

      --
      Business: www.adex-japan.com
      Pleasure: www.usefilm.com/member/roger
    • Michel Thoby
      ... Mark, thank you very much for sharing this link. I had found by myself the same way to mechanically set the focus scale ring at the correct position. I can
      Message 62 of 62 , Feb 10, 2014
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        Le 9 févr. 2014 à 23:22, <markdfink@...> <markdfink@...> a écrit :

        Absolutely don't trust the focus scales on any of their lenses! I found out the hard way with a 35mm that I rented, and see that both my 14mm and 8mm have the same issues. I used this link to find out how to fix it so that I can reliably use hyperfocal settings when shooting.


        Mark
        Mark, thank you very much for sharing this link. 
        I had found by myself the same way to mechanically set the focus scale ring at the correct position. I can confirm that it made me a happy user of the Samyang 14 mm for more than three years now. 
        I was inspired by Jeffrey R. Charles who had kindly taught us in 2009 how to solve the problem that similarly affects the Samyang 8 mm f3.5 fisheye lens. It is a simpler fix than for the rectilinear WA though:

        Best regards, 

        Michel Thoby
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