(Small Problems) with Stitching Panorama

Discussion in 'Photoshop Tutorials' started by Norm Dresner, Jul 5, 2005.

  1. Norm Dresner

    Norm Dresner Guest

    Problem 1
    While I was on the road from Leadville CO to Albuquerque NM, I stopped at a
    mountain lake and lacking a sufficiently wide angle lens (a lack which I've
    more-or-less just remedied on eBay), I stood in one spot and turned around
    slowly, taking several pictures at about 30 degrees apart. When I got home
    I installed the new Photoshop CS2 which had been sitting on the desk for 3
    weeks because everything else I had to do was adequately taken care of with
    the ancient 5.5 version.

    Anyway, when I went to stitch the pictures together, on the first try with
    all 6 images the program actually got the order wrong. I did it again,
    this time only using the first three to make one composite and the last
    three to make a second, intending to then join these. Before I did,
    however, I noticed that there's are two diagonal bands where --
    presumably -- the images were joined and there's a very (to my eye anyway
    but not to most other people) definite discontinuity in the image
    brightness.
    1. What's causing this?
    2. What's the best fix now that I have the images and can't retake the
    pictures?
    3. Is there anything I could have done while taking the pictures to
    avoid this?

    Problem 2
    I also took, panorama-style, 6 photographs of an old steam locomotive. But
    I was fairly close, maybe 20' away, and using a very wide angle lens (19mm
    on a 35mm DSLR) and the resulting image is distorted because the center
    section -- the one closest to me -- is much larger than the ones on either
    side. Am I correct in thinking that this is definitely not the way a
    close-up panorama should have been taken, i.e. rotating around a single
    point, and rather that I should have walked side to side with the camera at
    the same distance and same angle to the subject for each shot?

    Thanks in advance for all hints, links, URL's suggestions, and even
    constructive flames.

    Norm
     
    Norm Dresner, Jul 5, 2005
    #1
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  2. Norm Dresner

    Lorem Ipsum Guest

    Norm, we would have to see the pictures, but my tentative guess is that the
    individual pictures are not perfectly horizontally aligned, and you may also
    have let the camera auto-expose so that each frame is slightly different,
    especially in the skies, and the stitching algorithm simply did its best.
    Take an average reading and lock the camera's exposure to it for all
    exposures. Use a leveling tripod head. Increment evenly.
    That's the way it works: the closer image is larger, the more distant (the
    ends) is farther away. I had a client who thought a 12-mile wide panoramic
    shot from 600 feet up should look like one was driving by so that all images
    were unified in perspective. A sweeping pan doesn't work that way.
     
    Lorem Ipsum, Jul 5, 2005
    #2
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  3. Norm Dresner

    Hunt Guest

    There is probably a bit of edge fall-off in your lens, and the lighting most
    likely is different, as you panned. A couple of suggestions:

    1. PS CS2/Panorama (not its offical name), will allow you to do a pano two
    ways - where it flattens the image, and does the blending, or as Layers. If
    all is very good with the images, the flattened version will do a good bit of
    the blending. If not, then the Layers Option is the way to go. You can also
    move the individual parts around (or at least you could in CS) to get the
    order right. Now, for the Layers Option: Create Layer Masks so you can "paint"
    in, and out the overlap. Use Adjustment Layers (maybe with a gradient mask) to
    get your Layers looking exactly the same. I start at one end and correct it
    until I am satisfied, then move on to piece two, matching everything, and so
    on.
    In this case, you should have positioned yourself at one end of the train,
    looking down the length of it to find a spot that you could set up for all the
    other shots, which would all be parallel and close to equidistant from the
    subject. Try for a one-point perspective, i.e. perpendicular to the subject.
    Shoot frame 1. Move parallel to the subject, and frame up, creating some
    overlap - shoot frame two. Repeat as often as is necessary to capture all of
    the train. Try to keep camera the same height and distance from the train for
    all, focal length the exact same for all, and don't forget the overlap.

    You might be able to use Layers, and then distort the center images to match
    the perspective of the ends, though you will have to work (and a bunch of work
    it will be) with each image to get the exact distortion. Set up two horizontal
    grid lines (top of train at the smallest point, and bottom of train at
    smallest point) and then begin distorting the Layers to follow those guides.
    You might well surprise yourself with the results. Don't give up, until you
    have it. One problem will be that you are going to have a VERY horizontal
    image, and it will be small, because the ends of the train were farther from
    your camera.
    Good luck,
    Hunt
     
    Hunt, Jul 5, 2005
    #3
  4. Use a dedicated panorama stitching program, it's likely to do a far
    better job than Photoshop CS2. Panorama Tools + PTGUI + Enblend +
    AutoPano (2 programs, 2 plugins, PTGUI controls it all) does an
    absolutely incredible job of merging and blending, and uses *lots* of
    CPU time. You get excellent control over the merging process.

    Cheers,
    Nicholas Sherlock
     
    Nicholas Sherlock, Jul 5, 2005
    #4
  5. Norm Dresner

    Paul Mitchum Guest

    Differences in exposure between pictures, vignetting of the lens, or
    about a zillion other different things.
    Don't use Photoshop. Use hugin with enblend. Get it here:
    <http://hugin.sourceforge.net/>

    Also, IIRC, PS masks the different layers for each image, so you can
    fine-tune the masks to minimize the diagonal line effect.
    The best solution is to have a tripod and a special panoramic head. The
    head will let you mount the camera so that there are no parallax errors
    between the different images. Minus the special head, however, a stable
    tripod really helps.

    You also want all the pictures to be the exact same exposure (zoom,
    focus, shutter speed and f-stop, and for digital, ISO setting). This way
    you have the best chance of a good stitch.

    Again, you want hugin, or any of the PanoTools plugins for PS. They let
    you correct the fisheye effect.
     
    Paul Mitchum, Jul 5, 2005
    #5
  6. Norm Dresner

    Lorem Ipsum Guest

    In addition, the tripod should pivot about the nodal point of the lens, not
    from the tripod mount in the camera.
     
    Lorem Ipsum, Jul 5, 2005
    #6
  7. Norm Dresner

    Stephan Guest

    PS can be used to assemble panoramas but not using the panorama function.
    First you need to determine the nodal point of your lens.
    ttp://www.kaidan.com/nodalpoint.html
    http://www.path.unimelb.edu.au/~bernardk/tutorials/360/photo/nodal.html
    Second you need a precisely leveled tripod if you want strait horizons.
    Third you need to shoot manual and with a good lens and, very important,
    you need to correct your lens distortions, use something like the
    lensdoc plugin or panotool if you have time to learn.
    Then make a large canvas, import you picture in it. Place the pictures
    using the difference layer mode and when done create a layer mask for
    each layer.
    Use the Color Match function to equalize your skies, they will always
    need work, especially on sunny days.
    Now use black and white brushes and paint along on your masks to erase
    ghosts and objects that moved during your shoot, like cars, people waves
    or birds.
    It takes a bit of practice but you'll get perfect panos while all the
    automated solutions out there will produce crap. Now if you can afford
    it get Stitcher from Realviz and see the magic but you will still have
    to work a bit on your masks.

    Stephan
     
    Stephan, Jul 5, 2005
    #7
  8. Norm Dresner

    Paul Mitchum Guest

    Hence the special panoramic head.
     
    Paul Mitchum, Jul 6, 2005
    #8
  9. Norm Dresner

    Pat Ziegler Guest



    Allot of good suggestions, I would add, Do not use any type of auto
    exposure setting while taking the photographs. Look at the whole scene and
    choose a good manual setting that will work for the entire scene. This will
    lessen the need to tweak you levels in post.

    I do mine totally manually is PS CS2..

    Ziegler
     
    Pat Ziegler, Jul 6, 2005
    #9
  10. Norm Dresner

    me Guest

    I have always down this manually but I invariably get a difference in
    the colour, mostly sky as it changes from almost white getting close to
    the sun to a blue colour as we move away from it. Personally this
    doesn't really bother me as I haven't used mine for anything where it
    mattered, all I did before sticking them together was fiddle with the
    gamma, brightness and contrast a bit to get them vaguely similar.
     
    me, Jul 6, 2005
    #10
  11. Norm Dresner

    me Guest

    Down? Fool, mea culpa.
     
    me, Jul 6, 2005
    #11
  12. Download a trial copy of the shareware program Panorama Factory and give
    it a try on your images. It automatically corrects for vignetting,
    exposure mismatches, camera misalignment and can even figure out the
    focal length of your lens if it has too.
    Without paying you will get a watermark on the final image, but you
    can still evaluate the results.
    You can see lots of examples of this program in use on my web site for
    the 360 degree panoramas.
    The free panorama tools (even with the extra gui front end programs)
    is harder to use, especially for a beginner. Save it until you get
    really into panoramas.
    A panorama head is not really needed if the subject is more than about 8
    feet away. A levelled tripod helps a lot, but a bubble level on the
    camera can substitute in a pinch.
     
    Robert Feinman, Jul 6, 2005
    #12
  13. Norm Dresner

    Kingdom Guest

    Yup the PS pan is very poor, I use Canon PhotoStitch, simple fast and
    very very good.
     
    Kingdom, Jul 6, 2005
    #13
  14. Ah, fergeddaboutit. The special Pano head, worrying about the Nodal
    point. Yes, these are nice to know, and critical in some situations, but
    for an outdoor landscape Pano, not remotely necessary. It's more than
    possible to get great outdoor Panos hand held, but not recommended.

    Do set everything to manual, including white balance.
     
    John McWilliams, Jul 6, 2005
    #14
  15.  
    John McWilliams, Jul 6, 2005
    #15
  16. Norm Dresner

    Lorem Ipsum Guest

    Therein is the difference between professional results and the rest. I will
    stick to my pano head and handbuilt nodal point offsets.
     
    Lorem Ipsum, Jul 6, 2005
    #16
  17. Norm Dresner

    Lorem Ipsum Guest

    In other words, your experience is irrelevant to someone who wants to make a
    pano that does matter.
     
    Lorem Ipsum, Jul 6, 2005
    #17
  18. Norm Dresner

    Lorem Ipsum Guest

    What ever became of Apple's QTVR professional? Discontinued?
     
    Lorem Ipsum, Jul 6, 2005
    #18
  19. Apologies for the blank send.....
    No, you do not to know about the Nodal Point for this type of picture.

    Using good lenses you'll not have much distortion to correct. For now,
    fergeddaboudit.

    Using Photomerge, check off "Keep layers intact" or something to that
    effect. "Preserve Layers" is closer to the actual language, IIRC.
    All good, but somewhat advanced techniques.
    Wildly inaccurate statement. Using PS in a semi-automated way can
    produce stunning results. I've even lucked out with fully auto merges.
     
    John McWilliams, Jul 6, 2005
    #19
  20. Norm Dresner

    Clyde Guest

    Apple's QTVR Authoring Studio is officially still in Apple's catalog.
    However, you can't find much about it. Also, it has had zero support for
    years now and is still on version 1.1. If you get the right Apple person
    they will recommend Stitcher.

    If you want a legal copy of it, I have one to sell you. I wouldn't
    recommend it. I ran into bugs that are never going to be fixed. The big
    one being that it does NOT work in the Classic box in OS X. Apple made a
    big deal about how all OS 9 apps run in OS X. They own and sell an OS 9
    app that doesn't.

    Stitcher does work fine in OS X. So does PTMac and it's a heck of a lot
    cheaper while doing the same thing. (OK, PTMac doesn't do spherical.)

    Clyde
     
    Clyde, Jul 6, 2005
    #20
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