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It's the lookout tower below. You can't shoot from a single place - you take pictures from four different positions, distant a few meters one from another.

I know there logically must be problems on nearby trees (distant only tens to hundreds of meters) but I'd accept enblend retouching/blurring here.

What do I need to prevent are bumps on the horizon. There shouldn't be any as it is tens of kilometers away!

Note 1: I hoped I could add control points manually (without help of Hugin's CPFind) - on the horizon only - but the results have still been poor.

Note 2: Taken without a tripod. I assume it's not a problem though as I've taken tens of other panoramas handheld and they've been stitched perfectly in Hugin.

Lookout Tower enter image description here

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  • \$\begingroup\$ Was the horizon in the centre of the original images? It is on the pano, but maybe you cropped. \$\endgroup\$
    – Torsten Bronger
    Feb 7, 2016 at 22:00
  • \$\begingroup\$ Is it really impossible that the bumps are due to the actual topology of the landscape? \$\endgroup\$
    – Torsten Bronger
    Feb 7, 2016 at 22:02
  • \$\begingroup\$ @Nope, they aren't - this is clearly visible in panorama at the original resolution. \$\endgroup\$
    – user681768917
    Feb 10, 2016 at 11:23

2 Answers 2

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It's hard to tell, but it looks like in the stitched image your camera might have been aimed slightly above the horizon in at least 2 of the unstitched shots. By aiming up a little bit, the horizon at the widest part of your image "curls upwards" somewhat. This effect is similar to barrel distortion, and is more prominent with wider fields of view (shorter focal length lenses).

The solution is two-fold:

  1. Make sure your camera is absolutely level to the horizon. Use a bubble/spirit level on your tripod to determine this. In this case, it's the up/down tilt axis that is the most critical, that you're trying to resolve.

  2. Stitch together more shots, rather than fewer. The problem you want to avoid is distortion at the edges of the field of view. So increase the overlap for each successive shot (i.e., don't rotate as much between each shot, taking more shots). One way to do this is to rotate your camera to portrait orientation, and take your shots. You will be using the short axis of your sensor frame, thus requiring more shots to cover the same final stitched field of view as you would if used your camera in landscape orientation.

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  • \$\begingroup\$ While my comment to the question aimed at a similar explanation, it is important to note that any distortions must not happen even if the camera is aimed above the horizon. My comment suggested that maybe correction of the lens distortion is not perfect. But actually, this is improbable. In other words: If the stitching process is working properly, you ca aim your camera at whatever you want. That's the point in stitching after all. \$\endgroup\$
    – Torsten Bronger
    Feb 8, 2016 at 9:55
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    \$\begingroup\$ @TorstenBronger the stitching process can only do so much. Because several (all? not sure) of the shots are from different vantage points, there will definitely be substantial parallax errors that Hugin will have to try to smooth over. Stitching software generally assumes either pure rotation between shots (cylindrical or spherical projection), or pure translation (dolly movement). Substantial deviations from those assumptions just makes the stitcher work harder. At that point, you begin to need conformal mapping to make perspective distortion corrections. \$\endgroup\$
    – scottbb ♦
    Feb 8, 2016 at 13:28
  • \$\begingroup\$ But not for the horizon line, which is at infinity. \$\endgroup\$
    – Torsten Bronger
    Feb 8, 2016 at 15:13
  • \$\begingroup\$ @TorstenBronger correct, but stitching is perpendicular (-ish) to the horizon, and the stitch line below the horizon will have more and more parallax error the further below the horizon you look, for the OP's pre-stitched shots. In that case, considering the OP has both pan and "dolly" movement between shots, by eliminating the vertical tilt axis from the shots, Hugin should be able to do a better job of stitching. \$\endgroup\$
    – scottbb ♦
    Feb 8, 2016 at 18:29
  • \$\begingroup\$ Whatever is affected on his images, the horizon line is also affected, and this is at infinity, so the cause cannot be parallax effects. \$\endgroup\$
    – Torsten Bronger
    Feb 8, 2016 at 20:12
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My guess is that you're not taking care to keep your camera level/consistent in pitch. When you change the orientation of the camera between member shots, you can get errors like this. I'd highly recommend shooting with a two or three-axis spirit level on the hotshoe. Most cameras will only show you if you're level in roll, not in roll and pitch.

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