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  • Slight problem adjusting a lens on a NN5...

    Hi !

    I have tried to bettter my camera position on my Nodal Ninja 5, using as usual a little screwdriver vertical, 2.5 feet away, and a balcony door, 25 feet behind it ! As I use a Nikon 10.5 (with lens-hood chopped ) on my D800 !

    I know how to check it: align precisely the screwdriver with the door (at the center ot the frame, take a shot, then rotate the camera 45 degrees left, take a shot, rotate the camera 90 degrees right, take a shot. Then check the 3 images (at 100%), centering the left and right images on the screwdriver. The screwdriver must be perfectly aligned with the door on the 3 images !

    The problem is, as you can see in the screen-copy below, the center shot is well centered ! On the LEFT image, the screwdriver is slightly on the left of the door.... but on the RIGHT one, the screwdriver is ALSO on the left !!! How come ?
    I join a vertical shot, to show that the longitudinal centering is OK too...

    Any idea of WHAT I can do to center properly the camera, laterally ?

    Many thanks in advance for your help...

    Jean-Pierre

  • #2
    Jean-Pierre, instead of taking one shot vertically down, try taking two, panning the head around by 180 degrees in between. Align defished images on the floor features and check for parallax shift of the central knob relative to the floor. If shift is present, that would indicate that the entrance pupil of the lens does not lie on the vertical axis of rotation. If you use PTGui or similar, you can align the images using control points only on the floor features and maybe output the central area in rectilinear projection as a layered PSD file for examination in Photoshop - as in the attached image, which has the upper layer set at 50% opacity.

    John

    Click image for larger version

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    Last edited by John Houghton; 04-17-2017, 03:45 PM.

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    • #3
      Thanks for the quick answer, John ! Indeed that's what I did ! Problem: the vertical shot I uploaded only show one view (plus the 2 diagonal lines I drew on PS), but I forgot to show the other one at 90 degrees, at 50% opacity !
      ...so the problem is still with the X and Y axis :-( !

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      • #4
        OK. The diagonal lines suggested that you believed that the centre of the knob should coincide exactly with the centre of the frame, which is often not the case. All I can suggest is that you do your best to minimize the alignment errors in the two angled shots, which is where the images will be joined. What happens in the centre of the frame is of no particular consequence. Try a lateral shift on the lower rail to see if the asymmetry can be corrected.

        One slightly worrying thing about your shots is the over exposure. See how the width of the vertical bars of the window frame varies considerably when you compare the top and middle areas. This cannot help when judging alignment. There appear to be features visible in the scene outside the room, and I would prefer to align the screwdriver with something much further away and correctly exposed. Shoot raw and correct chromatic aberration.

        John

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        • #5
          I use a shaved Nikon 10.5mm with a D800 and simply line up the gold ring with Vertical tilting axis on the Nodal Ninja and this works well for me.

          If you look at the Nikon 10.5mm diagram at http://hugha.co.uk/NodalPoint/Index.htm you can see that this is a good compromise given the spread of the possible locations for the NPP.
          As a generalisation it is often recommended choosing a NPP where the incoming ray is at the same angle as the "join" between the images so you would chose a point further back from the front of the lens for more shots round.

          Looking at your second image of the screw driver aligned with balcony door I would suggest that you have actually found a good result.
          If you look at the images of the dowel aligned with the apex of the house roof you can see that an incorrect choice for the NPP shows up with a noticeable displacement in the images.

          Most of the shots in the Churches and those for Properties and the Shop on http://360hugh.co.uk/panormas/ were shot with the Nikon 10.5mm set up with the gold ring aligned with the Vertical tilting axis although at that time I was using an APS-C body.
          I have since shaved the Nikon 10.5mm to use with my D800 and still use the same set up.

          Hope this helps, Hugh.

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          • #6
            Originally posted by John Houghton View Post
            ....One slightly worrying thing about your shots is the over exposure.
            The overexposure is on purpose! Due to the very big differences between the inside and the background, I chose to only keep the screwdriver and the vertical mount of the door, this being the most important, isn't it ?
            ;-)

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            • #7
              Hi Hugh !
              Thanks for the tips ! I will try again (as I have all the possible free time)... That'll keeps me busy for sometime ! Then, as I also have a Samyang 12mm f/2.8, I will do the same... I should be busy for some time :-) !
              J-P.

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              • #8
                Originally posted by JPSCHE View Post
                That'll keeps me busy for sometime ! Then, as I also have a Samyang 12mm f/2.8, I will do the same... I should be busy for some time.
                It really isn't necessary to spend a lot of time on setting up your panorama head. I rarely spend more than 10 minutes on the job, and I do it quite often for various combinations of equipment. Remember that you cannot entirely eliminate all parallax problems in the case of a fisheye lens because of the variation in the apparent position of the entrance pupil for rays of light entering the lens from different directions. See http://www.johnhpanos.com/epcalib.htm .

                John

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                • #9
                  Hello J-P,

                  Unfortunately I only have a Samyang 8mm so cannot help with your Samyang 12mm, but you may find this page useful:
                  http://wiki.panotools.org/Entrance_Pupil_Database

                  As John states "It really isn't necessary to spend a lot of time on setting up your panorama head. I rarely spend more than 10 minutes on the job, and I do it quite often for various combinations of equipment. Remember that you cannot entirely eliminate all parallax problems in the case of a fisheye lens because of the variation in the apparent position of the entrance pupil for rays of light entering the lens from different directions."
                  The main point is how your stitching software succeeds with your images.
                  I use PTGui and usually get "very good" when I Optimise the shots, with no need to do any more work, with my set ups.
                  It really depends on your subject matter.
                  If you are photographing the inside of aircraft cockpits or cars with the subject very close to the camera then it is more important to get the best point for the NPP, but for most subjects it is not too crucial and some of the examples in the link in my previous message do have objects close to the camera.
                  To test your set up chose a subject with lots of detail for Control Point generation (i.e. avoid blank walls) and see how things are.
                  Of course, if you are photographing trees in a breeze then it is going to be more difficult to get a good stitch.

                  It appears to me, from the photographs you posted, that you actually have a good set up for the Nikon 10.5mm so I would suggest you chose a good subject and see how things work out.

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                  • #10
                    Hi John and Hugh !

                    Thanks to remind me your article, John :-) ! Eventually, after trying a few more times, setting the latéral as well as the F/B positions, I managed to find an almost perfect centering of my Nikon 10.5 on the D800, mounted on the NN5 head !

                    Here are (if it can help anyone) 2 shots of the settings ! The first one is the setting latéral (camera looking vertically) and the second one the setting forward/backward (camera looking horizontally !

                    J-P.

                    Click image for larger version

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                    Last edited by JPSCHE; 04-19-2017, 10:13 AM.

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