Mark Phillips writes:
> > > P.S. I have also tried Hugin, which I could not get to work,
[ ... ]
> I had a lot of trouble creating the points. I installed Hugin from the
> Debian respositories (v 2010.0.0.5045) and out of the box I got the error
> message about the non-free point calculating module. I then installed

I've found, with Hugin, that either it does brilliantly in automatic
mode, finding all the control points and doing all the stitching on
its own, or else it fails miserably for no obvious reason and
recovering and making it work is quite tricky. I seldom hit cases
where setting manual control points makes that much difference,
even when the control points it chose seem poorly placed.

One failure mode I see a lot turned out to be just the projection:
it stitched all the images reasonably but then smushed the result up
against the top so you couldn't see anything. I ended up upgrading
to a newer version at
which gave me more options for recovery, but it still ended up being
more trouble than it was worth in a lot of cases.
I wrote a couple of articles on on it that might help:

Ofnuts writes:
> Your shadow on the seam is caused by a general color mismatch between 
> the right part of the left image and the left part of the right one. 
> Creating panoramas requires to set the camera in manual mode to make 
> sure it won't change exposure parameters between the various shots. And 

"Requires" is a bit strong -- I've stitched lots of panoramas from
handheld auto-exposed sets. It certainly makes it easier.

But if you (Mark) have the layer masks in place, you shouldn't get
a sharp vertical band where two images meet -- the gradient in the
layer mask should take care of that. So it might be worth checking
your layer masks (e.g. alt-click on the mask's thumbnail, or use
Show Layer Mask) to make sure the gradient is really where you expect.

For instance, you can see the sky change color about 1/3 from the left in
but it's not a sharp band because of the layer mask gradient.

Sometimes it helps to make the gradient wider, or to take a big
fuzzy brush and paint some grey to make the two areas merge more
smoothly. If it's just one image causing the problem, you can use
Brightness/Contrast, Levels or Curves on it to make it better match
the image next to it; but in a panorama with a lot of images, that
gets tedious fast if you want them all to match, and you still end
up with color changes like in my confluence pan.

> To make it short, assembling panoramas in Gimp is a lot of hard work. 
[ ... ]
> Invest you time in making Hugin work. This will be a lot more rewarding 
> in the end.

I've found that I can usually get reasonably okay looking panoramas
from GIMP without too much work, just some fiddling with the
gradients and a little hand painting in the mask. But they're not
perfect, and I do agree, Hugin does a much better job than you'll
get with GIMP. And when Hugin works, it's super easy.  These days,
I always try Hugin first for panoramas, and I only fall back on GIMP
for the occasional set that Hugin won't handle.

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