An elementary question on overlap

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  1. An elementary question on overlap

    #1

    Hello all,

    I'm new to this forum and considering the acquisition of an NN5/RD8 setup.
    Hopefully, someone can enlighten me.

    I have taken 'typical' panos by simply rotating my rig on the tripod,
    and arbitrarily adding about 10-20% overlap between my images.
    Then of course, post process/stitching.

    When I look at the rotator specs I see numbers like 18 degrees/ 20 stops,
    30 degrees/12 stops, etc.
    They all work out to an exact 360 degrees and I fail to see where the 'overlap' comes into play.

    My only guess is that when using the settings in the camera/lens database,
    the nodal point setup accounts for an overlap to be added among the image sets taken.
    Also, when setting up a 'non-standard' body/lens with Fanotec's instructions,
    the same 'overlap' will be taken into account.

    Am I on the right track, or am I just a dimwit.
    (I'd ask my wife the same question, but I already know her answer)

    Any feedback is appreciated...thanks for your patience.

    cheers,
    Enrico

    "paddle faster...I hear banjo music"
  2. Re: An elementary question on overlap

    #2
    Users Country Flag
    Join Date: Aug 2008
    Location: Netherlands
    Posts: 1,740

    Hi enrico,

    In the database all the data is inclusive the overlap.

    Use this link, http://www.frankvanderpol.nl/fov_pan_calc.htm. I prefer 30% overlap to be more secure. Depends on the shooting site. You have to use the amount of pictures you have to take to find about the degrees you have to set on the rotator.


    Heinz

  3. Re: An elementary question on overlap

    #3

    Quote Originally Posted by enrico_953 View Post
    When I look at the rotator specs I see numbers like 18 degrees/ 20 stops,
    30 degrees/12 stops, etc.
    They all work out to an exact 360 degrees and I fail to see where the 'overlap' comes into play.
    The overlap comes from using a lens that has a wider field of view than the angle between click stops.
  4. Re: An elementary question on overlap

    #4
    Users Country Flag
    Join Date: May 2009
    Location: San Mateo, California
    Posts: 19

    Hello Enrico,

    To me, overlap is needed for your stitching software to correlate common patterns between two pictures.

    You already found out that your rotator has "stops" and "degrees" and sure enough, stops x degrees = 360¬?. So, in your example, 18 degrees / 20 stops means that tour rotator will allow you to stop 20 times, every 18 degrees in a 360¬? cycle.

    Heinz is right, 30% is a good start. The keyword though is "start". Your rotator has a finite amount of stops so in the end, it's the number of stops you key into your rotator that will set your amount of overlap.

    Let me show you how:
    Here's a link to an excellent book that has a pano calculator http://www.hdrlabs.com/tools/panocalc.html And yes, Heinz gave you the link to the creator of that pano calculator!
    Section 1: set your sensor data and the lens focal (the wider the lens, the less stops on your rotator)
    Section 2: function of your focal length and sensor dimensions, you get the Horizontal and Vertical Field of Vision (FOV). Note: the Vertival FOV of a portrait picture equals the Horizontal FOV on a landscape picture.
    Section 3: Now that you know the FOV, enter the desired overlap and the calculator gives a theoretical number of images.

    Now, this number of images is rarely an integer. You have to round it up....to match the number of stops on your rotator.

    The whole purpose of Section 4 is to recalculate the overlap given the fact that your rounded up the amount of images...

    I went through this exercise not too long ago for my D700 + RD16 rotator. Here's the result:I've added the theoretical number of images, and the rounding up to accommodate that the RD16 can do...

    I hope I did not go too deep... in summary:
    - overlap is necessary for panoramic softwares to stitch images properly
    - the actual overlap is driven by a combination of your lens orientation (portrait/landscape), focal and rotator setup
    - too little overlap will cause an improper stitching, too much overlap isn't good either (especially for your point of no parallax isn't set properly/close objects). Keeping overlaps values in mind is a must (in fact, I laminated the table in the PDF attached - and carry this table with my pano head!)

    Cheers!

    Philippe

  5. Re: An elementary question on overlap

    #5

    Interesting link you suggested.
    On my side, I have worked on excel format to calculate it regarding the position on the sphere, the angular step on the panoramic head and of course the minimum overlap you want.
    The only issue is that it is in french for the time being : Panorama calculator



    My blog : Aslan Resimler
  6. Re: An elementary question on overlap

    #6
    Users Country Flag
    Join Date: May 2009
    Location: San Mateo, California
    Posts: 19

    Hi Yves,

    I found your spreadsheet equally interesting. Do you need help translating it? Let me know!

    Bonjour Yves,
    J'ai trouve votre feuille de calcul forte interessante. Avez vous besoin d'aide pour la traduction? Dites mpi quoi.

    Thanks/Merci!

    Philippe
  7. Re: An elementary question on overlap

    #7

    Thank you for your support.
    In fact, I just need time to translate it it and I had some people asking for that new file.
    That is why I decided to put it online without the english and turkish translation.
    I guess that by the end of this week I will add the english translation.
    Thank you again.



    My blog : Aslan Resimler
  8. Re: An elementary question on overlap

    #8

    OK, translation in english is done :
    Panorama calculator



    My blog : Aslan Resimler
  9. Re: An elementary question on overlap

    #9
    Users Country Flag
    Join Date: Apr 2008
    Location: Hong Kong
    Posts: 2,388

    Quote Originally Posted by YvesG View Post
    OK, translation in english is done :
    Panorama calculator
    Hi YvesG,

    Thx for the calculator and video.
    I don't understand the 2 results in your "results details" table. what is +/-15 deg and +/- 60 deg? what is 60 deg and 130 deg?


    Nick



    Fanotec
    We listen. We try harder.
  10. Re: An elementary question on overlap

    #10

    That means you need to shoot a first line at +15¬? and a second line at +60¬?.
    And then you have to do the same at -15¬? and -60¬?.
    Those angles are the one you can read on the arm that is supporting the camera (I am calling it the upper arm).
    I don't know if I am clear enough.



    My blog : Aslan Resimler
  11. Re: An elementary question on overlap

    #11
    Users Country Flag
    Join Date: Apr 2008
    Location: Hong Kong
    Posts: 2,388

    Quote Originally Posted by YvesG View Post
    That means you need to shoot a first line at +15¬? and a second line at +60¬?.
    And then you have to do the same at -15¬? and -60¬?.
    Those angles are the one you can read on the arm that is supporting the camera (I am calling it the upper arm).
    I don't know if I am clear enough.
    thx. that makes sense. what does 130 deg refer to?


    Nick



    Fanotec
    We listen. We try harder.
  12. Re: An elementary question on overlap

    #12

    The second angle is linked to the horizontal rotation.
    That mean you will have to take a picture every 130¬?.
    Last information under this angle, is the number of pictures to be taken.



    My blog : Aslan Resimler
  13. Re: An elementary question on overlap

    #13
    Users Country Flag
    Join Date: Apr 2008
    Location: Hong Kong
    Posts: 2,388

    Quote Originally Posted by YvesG View Post
    The second angle is linked to the horizontal rotation.
    That mean you will have to take a picture every 130¬?.
    Last information under this angle, is the number of pictures to be taken.
    I am lost. Take a picture every 130 deg for 17mm eq?
    Besides why are the results different in French and English spreadsheets?


    nick



    Fanotec
    We listen. We try harder.
  14. Re: An elementary question on overlap

    #14

    There has been a bug when I translated the file.
    To have same results, you have to select again the camera position.
    Put the camera in vertical position and you will see that the final result is updated then.
    Sorry for that, I am immediately updating the file to be downloaded.
    Thank you.



    My blog : Aslan Resimler
  15. Re: An elementary question on overlap

    #15
    Users Country Flag
    Join Date: Apr 2008
    Location: Hong Kong
    Posts: 2,388

    Quote Originally Posted by YvesG View Post
    There has been a bug when I translated the file.
    To have same results, you have to select again the camera position.
    Put the camera in vertical position and you will see that the final result is updated then.
    Sorry for that, I am immediately updating the file to be downloaded.
    Thank you.

    Hi YvesG,

    Puzzle solved. Is there a way to make a drop down list of sensor size? 35mm equivalent only works for 3:2 format sensor. It does not work for 4:3 or 16:9 sesnor.

    Great Job!

    Nick




    Fanotec
    We listen. We try harder.
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