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Curious on a few Things related to stitching and Nodal point

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  • Curious on a few Things related to stitching and Nodal point

    I use a Canon 30D and Canon 10-22 ef-s lens. I have a few questions

    1. First question is what kind of lens is this? Rectilinear, full frame?

    2. If I try create a Pano using PTGUI pro and let the program automatically choose the lens parameters it tells me my lens type is full frame is this correct? Also it tells me focal length is 12.4 when I know I shot at 10mm why is this?

    3. My camera is a 1.6x crop sensor; however PTgui tells me it is 1.5869778. Now I know 1.6 is the rounded off figure but which one is more accurate? And which value should I use?

    4. Is it more accurate to manually input the Data? If so should I put this in? Lens type = rectilinear focal length =10mm Focal length multiplier = 1.5869778

    5. How do I work this calculator? ( To apply my example above I would put 10mm into focal Length, Size utilization=100%, Film/CCD length = 22.5mm or is 22.684627mm (according to my EXIF data in Ptgui) more accurate to use?, Film/CCD width =15.0mm or is 15.123085 (according to my EXIF data in Ptgui) more accurate to use?

    6. How does one calibrate ones lens for optimum and consistent stitching?

    7. Is it more accurate to treat each of the pictures for distortion prior to stitching them? If so which program gives the best results? And also do I apply the same distortion corrections to each of the images in the sequence? I know PtGui can correct distortion put I would think a dedicated program like DXO optics pro would be more accurate what is your take on this?

    8. When trying top find the Nodal point and I try to set the position of the camera on the horizontal arm of the head so that the entrance pupil is laterally aligned with the rotation axis I make sure the axis point of the head (such as the central adjustment screw on the Nodal Ninja 5/RD-16 rotator head) should be centred in the image frame. However when I am at 10mm the centre of my camera frame is slightly before the central adjustment screw and when zoomed to 22mm is perfectly aligned - does that mean I am aligned optimally or not or should I compromise between the two?

    9. When optimising using PTgui should I click or unclick the Optimise lens field of view setting?

    These are just a few I can think of for now,



  • #2
    Re: Curious on a few Things related to stitching and Nodal point

    I forgot to add another question

    10. When using the grid method for accuratly trying to find the Nodal point what is the most appropriate Aperture to use? and where should I focus? Will the postion of my focus alter my nodal point result? will my chosen apeture alter my nodal point result? or will a combination of the two alter my Nodal point result?

    Thanks again


    • #3
      Re: Curious on a few Things related to stitching and Nodal point

      Another question,

      Is the 10-22 ef-s considered a fish eye lens?


      • #4
        Re: Curious on a few Things related to stitching and Nodal point

        That's a daunting list, but i'll do my best before taking to my bed:

        1. Rectilinear
        2. Tools->Options->Exif shows the rules being applied. Adjust to suit. PTGui is not responsible for what the exif data says.
        3. The focal length and crop factor are just parameters that PTGui uses to estimate the horizontal field of view (hfov) of the lens, which is what matters. Optimization will evaluate the true hfov.
        4. How do you know if the focal length is 10mm rather than 12.4mm? It won't make any difference which you use for a 360 degree panorama.
        5. I never use such calculators myself. is good for 360x180 panoramas, otherwise I let PTGui calculate things for me.
        6. By shooting a 360x180 panorama in a favourable venu (large - to avoid parallax effects - with lots of features in all directions for control points). Set up the pano head as accurately as possible. Use the optimizer intelligently to get the optimum image alignment and the lens parameters will be found. The resultant project file may be used as a template for subsequent stitches of similar shoots. For a more exotic method, see
        7. No pre-processing of the images is necessary. Distortion is not going to vary from shot to shot if you don't change anything.
        8. .
        9. For 360 degree panoramas, lens fov should always be optimized.
        10. I haven't used the grid method myself, but I would set the lens focus position as you would for a normal panorama. (The position of the entrance pupil will usually vary with focus). Use f/8 or more. The aperture setting will not affect the entrance pupil position.
        11. The 10-22mm ef-s is rectilinear. (The manufacturer will clearly state if a lens is a fisheye).



        • #5
          Re: Curious on a few Things related to stitching and Nodal point

          Hey Mike,
          wow - a real list of questions. It was very good of John to spend the time in trying to answer them all.
          While I don't want to put you off our forum we are more geared towards support for the Fanotec product line. We welcome any and all questions outside the realm of actual product support but you may not get all the answers you seek. We are a small forum with only a hand full of regular users. For broader based questions try LOTS of regular and real chatty users there - and I mean that in a good way
          Plus not many will tackle so many questions in a single post. It's good to isolate particular questions to specific threads. It sounds like you have a few questions about PTGui - have you explored their website and tutorials? It's a great resource!
          Hope these two links help.
          thx Bill