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Re: [PanoToolsNG] Samyang 8mm

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  • A Kielcz
    Roger, I get for some reason a sharper image and DOF with setting at F6.7-8 and prefocus at .7m. Why, I don t know. I read a longtime ago on this forum about
    Message 1 of 62 , Nov 1, 2010
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      Roger,
      I get for some reason a sharper image and DOF with setting at F6.7-8 and prefocus at .7m.
      Why, I don't know.
      I read a longtime ago on this forum about optimal settings for this lens, but forgot what they were. Maybe other owners would remind me.
      Thank you!

      A Kielcz

      Cincinnati, Ohio, U.S.A.

      --- On Mon, 11/1/10, Roger D. Williams <roger@...> wrote:

      From: Roger D. Williams <roger@...>
      Subject: Re: [PanoToolsNG] Samyang 8mm
      To: PanoToolsNG@yahoogroups.com
      Date: Monday, November 1, 2010, 11:03 AM







       









      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























      [Non-text portions of this message have been removed]
    • 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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