Trouble With Pano's with High vertical Arc's

Discussion in 'General Technical Discussion' started by lexiticus, Jul 31, 2007.

  1. Ok I use PTgui because it does an amazing job with massize amounts of pictures, But I also have autostitch on my computer to test when PTgui messes up (Never does a better job unofrtunately)

    But today I tried taking pano's with a larger than typical vertical arc, A full 180 degrees from ground to Sky, And then I tested a whole 90 degree stitch job, And both times PTgui Rendered it has an almost mushroom effect on the top (it stretches very thin and very wide.

    Now I'm wondering what anyone does to fix that, or render larger degree of vision panoramics without making them look like crap.

    I'll put up a screenshot of what I mean in a sec.
    (Here is about a 80 degree vertical arc pic that loses all sharpness and stretches out near the top)
    blend.

    (One panoramic I have is a 360 degree vision all around, But its impossible to stitch properly... But even pics that don't go all the way around horizontally still have major issues with both programs.)
     
  2. bump, anyone?
     
  3. Gale

    Gale

    978
    Jan 26, 2005
    Viera Fl
    Try over in the retouching forum here or on dpreview retouching forum

    I haven't a clue even how to shoot one

    I sure love the light in that image very pretty
     
  4. Try different projection options, if available (spherical/rectangular/cylindric). Maybe that helps.
     
  5. Tried them all, I think my only option is to do the skinny verticals on their side (so it thinks they are horizontal) And just forget wide pano's with more than say 50 degrees of arc above and below the horizon.
     
  6. yamo

    yamo

    Jun 28, 2007
    Santa Cruz, CA
    Greetings. As far as I can tell from your description the "problem" what your seeing is actually a "feature" of projection (projecting a spherical space onto a two-dimensional image).

    A couple of things you can try to achieve a pleasing result:
    - move the aligned group of images with respect to the center of the pano editor screen. In your example move the mid to higher part of the trees to the vertical center and optimize. This will of course push the distortion to the lower part of the image but perhaps you can find a pleasing balance.
    - play with the yaw, pitch, roll parameters under the optimizer (I've not done this but it looks like the place to work some of these issues)
    - post-process the pano with PS or DXO to fix distortions.

    just some ideas...

    Cheers,

    -Yamo-
     
  7. yamo

    yamo

    Jun 28, 2007
    Santa Cruz, CA
    Greetings, again. I played with the yaw, pitch & roll and it didn't help (as far as I could tell), but you might try this:

    In the ptGUI Panorama Editor window click on the option "Edit Entire Panorama" (the third icon from the left). Left click and hold the group of images and drag up and down. You will see the distortion change from top to bottom depending on where the center of the group of images is. Balance the distortion to taste.
    Also you might notice that as you click through the different projections (rectilinear, cylindrical and spherical) that the aspect ratio of the editing screen changes. I would hazard a guess that the cylindrical projection would offer the least top to bottom distortion (the mushroom/hourglass shape).

    Anyway, just some more thoughts...

    By the way, I notice you're form Kelowna. I traveled through there once many years ago (we were picking up a Standard Poodle puppy from a breeder in Vernon). I remember it as very beautiful country...

    Cheers,

    -Yamo-
     
  8. Ahh ok, so it looks like I don't have many options, For extreme verticals (without the width) I will do everything sideways, (to fool the program) Because even after raising the "horizon" level, with the Edit Entire Panorama feature, The trees up top were still all stretched out. In my example the Horizon was even about 1/8th of the image above true horizon. So I guess I'll just stick with the tried tested and true methods that worked before!

    I knew it wouldn't be easy to make the height and width work together, Because of the whole 3d image on a flat screen problem, But I tried anyway!

    Also Kelowna is a pretty nice City to live in to take pictures, The Agricultural Land Reserve laws keeps it from getting too developed, And there is all 4 seasons (sometimes in extremes). So as long as its not too dry I'm pretty lucky! I can drive for 10 minutes in any direction and find something worth taking pictures of!
     
  9. lexicitus,

    Pardon me if I'm incorrect here, but it seems you are asking a Volkswagen to perform like a Lamborghini! If you want to correct perspective, you have to have a way to include swings, shifts and tilts between your lens and the image plane. In other words, you need a view camera.............not a DSLR. These "35mm type" cameras are extremely limited. Can't expect them to do what you are asking....................and I'm not aquainted with a computer program which will correct the problem either.
     
  10. Hmm I never thought of a tilt shift lens helping here, But I don't have one anyway so I guess I won't worry aobut it.

    I don't mind the perspective being all out of whack, Sometimes that makes it look neat, I just don't want Stretched blurry images. For example, Horizontal pano's (with the Cylindrical guide) are laid out without any perspective going from left to right, you merely look and see more, Thats what I wanted to do with the vertical axis, So by rotating them I can handle a bit more of that.

    It won't work for the pictures I have already taken, But in the future I will know!
     
  11. JeffKohn

    JeffKohn

    Apr 21, 2005
    Houston, TX
    I've run into this same problem, although it wasn't quite as extreme as yours. I was shooting Horseshoe Bend Canyon. My vertical FOV was only about 70 degrees (horizontal FOV was around 180), but I think the fact that I was shooting at a downward angle made things more problematic.

    I tried stitching in both PTGui (latest version) and AutoPano Pro. In both programs, the spherical projection squashed the image too much vertically, and the cylindrical projection squashed the image horizontally. Neither projection looked natural, they both went too far. In the end, I used the spherical projection and then stretched it back out a bit in Photoshop and applied some correction in the Lens Distortion filter. Unfortunately I don't think that will work for your shots becuase it looks like the distortion is just at the top.

    What these stitching programs really need is a "flat stitch" mode that doesn't do any projection. I think for some images this would actually be preferable. It would also be the correct way to stitch images taken with a shift lens.

    You can do a flat stitchin in CS3's Photomerge by choosing "Reposition Only", might be worth a try for your images. It didn't work for me because Photomerge was unable to produce a clean stitch.
     
  12. Great advice, I might have to try out CS3 now! I was prefectly happy with CS2 so far!

     
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