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Questions about 10-17mm zoom fisheye

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  • Roger D. Williams
    Today I traded in my lovingly acquired collection of M42-mount lenses and the Cosina Bessaflex I used them with for a Pentax 10-17mm zoom fisheye for my Pentax
    Message 1 of 6 , Jul 31, 2010
      Today I traded in my lovingly acquired collection of M42-mount lenses
      and the Cosina Bessaflex I used them with for a Pentax 10-17mm zoom
      fisheye for my Pentax K-x. Apart from twin Cosina film cameras I
      yoke together to take stereo slides, I am now "all digital." Why
      doesn't that feel too good, I wonder...

      Question 1

      Can someone point me to where the NPP point for this lens is, used for
      shots 60 degrees apart, i.e., six around, at the 10mm focal length?

      I know the Tokina version of this lens, which is available in Nikon
      and Canon mounts, is in much wider use than the Pentax version, but
      I am hoping that someone knows the NPP, perhaps expressed in mm from
      the front glass? Or some other non-variable feature of the lens?

      Since I have a cataract in my dominant (right) eye I am not too good
      at spotting details with it, so finding the NPP spot is not so easy.
      (And yes, I do know about operations to remove cataracts...)

      Question 2

      I have several times read that twisting the camera so that the
      diagonal of the sensor frame is vertical is no help if you have
      a lens that already fills the entire frame. I don't see that...
      If you put the diagonal vertical, you will reduce the size of any
      nadir or zenith holes and may even eliminate them. That seems to
      be a real advantage. Of is there some factor I am ignoring, like
      some reduction in the overlap between adjacent shots?

      I am going to try it tomorrow, but wondered if anyone in the group
      has demonstrated this to their own satisfaction.

      Roger W.

      --
      Business: www.adex-japan.com
      Pleasure: www.usefilm.com/member/roger
    • John Houghton
      ... Roger, The problem is that you don t get nice tidy circular holes. They become more like a circular saw shape or like the petals of a flower. Try varying
      Message 2 of 6 , Jul 31, 2010
        --- In PanoToolsNG@yahoogroups.com, "Roger D. Williams" <roger@...> wrote:
        > Question 2
        >
        > I have several times read that twisting the camera so that the
        > diagonal of the sensor frame is vertical is no help if you have
        > a lens that already fills the entire frame. I don't see that...
        > If you put the diagonal vertical, you will reduce the size of any
        > nadir or zenith holes and may even eliminate them.

        Roger, The problem is that you don't get nice tidy circular holes. They become more like a circular saw shape or like the petals of a flower. Try varying pitch and roll of some sample images in PTGui and you will see what I mean.

        John
      • mick crane
        ... it is really confusing like that and holding a pole horizontally to decide which is up
        Message 3 of 6 , Jul 31, 2010
          On Sat, July 31, 2010 7:41 pm, John Houghton wrote:
          > --- In PanoToolsNG@yahoogroups.com, "Roger D. Williams" <roger@...>
          > wrote:
          >
          >> Question 2
          >>
          >>
          >> I have several times read that twisting the camera so that the
          >> diagonal of the sensor frame is vertical is no help if you have a lens
          >> that already fills the entire frame. I don't see that... If you put the
          >> diagonal vertical, you will reduce the size of any nadir or zenith holes
          >> and may even eliminate them.
          >
          > Roger, The problem is that you don't get nice tidy circular holes. They
          > become more like a circular saw shape or like the petals of a flower.
          > Try varying pitch and roll of some sample images in PTGui and you will
          > see what I mean.
          >
          it is really confusing like that and holding a pole horizontally to decide
          which is up
        • Roger D. Williams
          On Sun, 01 Aug 2010 03:41:00 +0900, John Houghton ... I know what you mean, John, and saw this for myself when I tried to get my 10.5mm Nikon full-frame
          Message 4 of 6 , Jul 31, 2010
            On Sun, 01 Aug 2010 03:41:00 +0900, John Houghton
            <j.houghton@...> wrote:

            > --- In PanoToolsNG@yahoogroups.com, "Roger D. Williams" <roger@...>
            > wrote:
            >> Question 2
            >>
            >> I have several times read that twisting the camera so that the
            >> diagonal of the sensor frame is vertical is no help if you have
            >> a lens that already fills the entire frame. I don't see that...
            >> If you put the diagonal vertical, you will reduce the size of any
            >> nadir or zenith holes and may even eliminate them.
            >
            > Roger, The problem is that you don't get nice tidy circular holes. They
            > become more like a circular saw shape or like the petals of a flower.
            > Try varying pitch and roll of some sample images in PTGui and you will
            > see what I mean.

            I know what you mean, John, and saw this for myself when I tried to
            get my 10.5mm Nikon full-frame fisheye to give me four-around by
            tilting it. The "petals" were huge and quite intractable.

            But, but, BUT! The only problem I'll have with this lens + six around
            is the need to fill the nadir and zenith. I thought that if I tilted
            the camera and lens until the 180-degree diameter stretched from top
            to bottom of the images, I might do away with the holes altogether.

            The Pentax\Tokina does have 180-degree FOV along the diagonal at
            the 10mm end, if I remember right. Well, I'll soon know... <grin>

            I saw such good things written about the 10-17mm zoom fisheye
            that I wanted to give it a go. I hesitated over the considerably more
            expensive Sigma 8-16mm rectilinear lens because I know I could get
            good use out of that for general photography, but eventually plumped
            for my FIFTH fisheye lens (after Zenit, Peleng, Nikon and Sigma).
            I can always "de-fish" the images...

            Will report back later on the results...

            Roger W.

            --
            Business: www.adex-japan.com
            Pleasure: www.usefilm.com/member/roger
          • Erik Krause
            ... You mean the Tokina 10-17mm f3.5 DX? http://wiki.panotools.org/Entrance_Pupil_Database has a value... -- Erik Krause http://www.erik-krause.de
            Message 5 of 6 , Aug 1, 2010
              Am 31.07.2010 14:56, schrieb Roger D. Williams:
              > I know the Tokina version of this lens, which is available in Nikon
              > and Canon mounts, is in much wider use than the Pentax version, but
              > I am hoping that someone knows the NPP, perhaps expressed in mm from
              > the front glass? Or some other non-variable feature of the lens?

              You mean the Tokina 10-17mm f3.5 DX?
              http://wiki.panotools.org/Entrance_Pupil_Database has a value...

              --
              Erik Krause
              http://www.erik-krause.de
            • Roger D. Williams
              ... Thank you very much, Erik. Exactly what I wanted to know. I must remember to look in the Wiki every time I have a query, it so often has the answer. I
              Message 6 of 6 , Aug 1, 2010
                On Mon, 02 Aug 2010 04:11:56 +0900, Erik Krause <erik.krause@...> wrote:

                > Am 31.07.2010 14:56, schrieb Roger D. Williams:
                >> I know the Tokina version of this lens, which is available in Nikon
                >> and Canon mounts, is in much wider use than the Pentax version, but
                >> I am hoping that someone knows the NPP, perhaps expressed in mm from
                >> the front glass? Or some other non-variable feature of the lens?
                >
                > You mean the Tokina 10-17mm f3.5 DX?
                > http://wiki.panotools.org/Entrance_Pupil_Database has a value...


                Thank you very much, Erik. Exactly what I wanted to know. I must remember
                to look in the Wiki every time I have a query, it so often has the answer.
                I cannot really understand my reluctance to use a Wiki, but it is generally
                the LAST place I think of.

                Roger W.

                --
                Business: www.adex-japan.com
                Pleasure: www.usefilm.com/member/roger
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