straighten panorama

Discussion in 'Photoshop Tutorials' started by frederic pichon, Sep 2, 2005.

  1. my soft to make Panoramas (photostich) often ends up doing them on a curve.
    How can I straighten up the picture, ie decurve an image?
    thanx
     
    frederic pichon, Sep 2, 2005
    #1
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  2. First you'll need to start with using a leveled tripod when shooting.
    Next you could use a different stitching utility, allowing to control
    yaw, pitch, and roll. The pitch and roll parameters can be used to
    distribute the tripod leveling errors evenly over the composite image.

    Bart
     
    Bart van der Wolf, Sep 3, 2005
    #2
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  3. frederic pichon

    Harvey Guest

    Harvey, Sep 3, 2005
    #3
  4. frederic pichon

    Clyde Guest

    It is often more than that. A curved pano is due to the camera being
    pointed slightly up or down during taking. It is almost impossible to
    keep it level by hand. You are right that a leveled tripod will fix that.

    I have a big, heavy pano head on a great tripod that will do that just
    fine. However, it's all rather big and heavy. So, I find that I rarely
    take it with me.

    Luckily my Hugin frontend to Panotools will stitch it very nicely.
    However, it takes more that control points for the yaw, pitch, and roll
    to correct a curved horizon.

    I have found that the best and easiest way to correct the curve of the
    horizon in Hugin is to have an object on each end of the pano that is
    vertical. Horizontal will work too. You then put in a "vertical line"
    set of control points. Do this for one frame on each end, giving you two
    vertical lines. Hugin/PT will straighten everything up just fine.

    Of course, you don't always have anything straight in a pano. Landscapes
    are particularly bad for having nothing to line up to. I have tried to
    skew bits of the picture at a time in Photoshop, but it's a pain. It
    hasn't been very satisfactory either.

    I usually stitch the pano and leave the curve in. Then Enblend. Then I
    open the pano in Hugin as one image. I then apply an artificial horizon
    using the same control point method as above. The difference is to make
    one horizontal line from the center to the right side and another from
    the center to the left side. You are likely to have to do it over
    several times until you get it looking right.

    None of these techniques work very well for 360 degree panos. I have
    found that handheld 360 panos are almost impossible to get straight and
    not wavy. The pano head on a tripod will be what you want for 360.

    Clyde
     
    Clyde, Sep 3, 2005
    #4
  5. frederic pichon

    Lorem Ipsum Guest

    Someone else can point you to software tips, but permit me to point out the
    common errors made in panoramic. Solve the 'at the camera' issues first, and
    the software will be happy to do proper stitching.

    A tripod is necessary. Use a leveling head such as the Manfrotto 3416. It
    will maintain level through 360 degrees with minimal hassle. Make certain
    your frames are of equal degrees, and make enough frames so that horizontal
    distortion is minimized. See the Manfrotto 300n for a very nice unit that
    goes on top of the 3416. Turn off autofocus. On many auto-everything cameras
    the focus will hunt between shorts. Turn off autoexposure! Expose for the
    brightest part of the scene, or within a reasonable lattitude. Finally, it
    is best to rotate the camera at the nodal point of the lens. I gave up on
    the manufactured units that accomplish the later because they are too flimsy
    or too expensive, and made my own. ...oh, and when you get everything set up
    right, a cloud will pass over the sun in the middle of your sequence and you
    will have to start all over. :)
     
    Lorem Ipsum, Sep 3, 2005
    #5
  6. well all this is good and fine for professional work, but I dont really feel
    like carrying a 4kg tripod on a 7 hrs hike to the top of the mountain, to
    take one souvenir picture...

    Thanks for Autostitch, which works much better indeed, although it is slow
    and seems to drastically reduce the definition of the original pics.
    I was more inquiring for a way to decurve an image, something like a
    negative spherisation, which would enable to define a base curve, and
    transform it into a straight line, like an anamorphose.

    PS doesnt do that??
     
    frederic pichon, Sep 4, 2005
    #6
  7. frederic pichon

    Lorem Ipsum Guest

    Filter - Distort - Spherize?
     
    Lorem Ipsum, Sep 4, 2005
    #7
  8. I suggest you try panorama factory. It's shareware and you can evaluate
    it before you decide to buy.
    It figures out everything for itself (although you can override and fine
    tune). It corrects for camera tilt, vignetting, barrel distortion and
    will produce cylindrical or spherical projections.
    Most of the 360 interactives on my web site were stitched with this.
    If you are using a digital camera it even has some special features for
    that as well.
     
    Robert Feinman, Sep 4, 2005
    #8
  9. frederic pichon

    Clyde Guest

    That way is a huge pain. Besides, I've never been successful with it.

    Clyde
     
    Clyde, Sep 4, 2005
    #9
  10. frederic pichon

    Lorem Ipsum Guest

    Sorry. I am not sympathetic. If people want true panoramas, then they have
    to make it in the camera first, or lower their expectations. The later seems
    to be the way most people go, so have at it.
     
    Lorem Ipsum, Sep 4, 2005
    #10
  11. Since you get the best results if you avoid the issues from the start,
    and at the same time want to travel light, try a spirit level in the
    camera's hotshoe when handholding the camera. You may also want to use
    a plumb-line type of string hanging from the lens (approx. entry pupil
    / nodal point) so you can keep constant height and rotation point. As
    a weight on the string you can use anything, like a carabiner.

    Bart
     
    Bart van der Wolf, Sep 5, 2005
    #11

  12. CS2 has the new mesh warp feature. Just the tool for what you want to do...
     
    Philip Rawson, Sep 5, 2005
    #12
  13. frederic pichon

    MetaMorph Guest

    Are U using a digital camera to do the panorama's?? If so - read on...

    I have just gone thru this process extensively - and I found something
    interesting.... The software used afterwards and whatever arrangement I had with
    the tripod (eg using a spirit level to get absolute level panning..) - none of
    that had any impact - I always got curved images. SO I took a look at the EXIF
    information in the file headers from the digital camera and noticed that the
    images I had been taking at the wide angle setting of the camera - had effective
    focal lengths of 8mm!!!! Even though on the camera I had selected wide angle
    and this was 35mm - the hi resolution CCD in my camera - 12,000 effective pixels
    - meant this was reduced from 35 to 8mm
    So I did the frames again - this time selecting a much lower resolution AND
    zoomed in the camera lens. This of course meant I got a lot more frames to
    stitch together - but at least I could easily do this now manually. The results
    using stitching software were even better (PTGui for example)..


    Hope this helps
     
    MetaMorph, Sep 5, 2005
    #13
  14. frederic pichon

    Lorem Ipsum Guest

    Distortion. Yep, you did the right thing to zoom out and make more pictures.
     
    Lorem Ipsum, Sep 5, 2005
    #14
  15. frederic pichon

    Clyde Guest

    Well, I did explain how to straighten curved horizon panos earlier in
    this thread. I do it all the time with Hugin/PanoTools. Well, if it's
    less than 360 degrees.

    Clyde
     
    Clyde, Sep 5, 2005
    #15
  16. frederic pichon

    MetaMorph Guest

    You mean ZOOM IN - zoom out gives a wider field and the problem I referred to!!

    :-(
     
    MetaMorph, Sep 6, 2005
    #16
  17. frederic pichon

    Clyde Guest

    Technically using a longer focal length won't solve the problem of
    curved horizons. It will make it less likely that you aim up or down.
    So, the curve is likely to be less pronounced. But curved horizons will
    still be there.

    The only to not have curved horizons is to keep the camera level.

    Clyde
     
    Clyde, Sep 6, 2005
    #17
  18. frederic pichon

    Hecate Guest

    ....or flatten the Earth ;-)

    --

    Hecate - The Real One

    Fashion: Buying things you don't need, with money
    you don't have, to impress people you don't like...
     
    Hecate, Sep 7, 2005
    #18
  19. frederic pichon

    Tom Nelson Guest

    Try this: take a long piece of light rope or heavy twine and tie a loop
    in the middle big enough to fit the lens through it. Tie the free ends
    together such that it supports the camera at eye level when you step on
    it with both feet (feet fairly wide apart).The rope defines a triangle
    with the base between your feet and the loop at the apex, with the
    camera lens in the loop. This arrangement is light and prevents
    side-to-side movement, though it does not prevent you from rocking
    forward and back. You pull up slightly with the camera to hold the rope
    taut. Use a mark in the viewfinder to hold the horizon level and the
    same distance from the top of all pictures. Try to pivot the camera
    around the loop as you take your pictures.

    Tom Nelson
    Tom Nelson Photography
     
    Tom Nelson, Sep 8, 2005
    #19
  20. frederic pichon

    Lorem Ipsum Guest

    That reads nicely, but does not work as you imagine it does.
     
    Lorem Ipsum, Sep 8, 2005
    #20
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