Adjusting control points after stitch; best practice

[tbransco]

Using hugin 2014.0.0. (win32) I just completed an 11-image panorama of a distant mountain range (no foreground detail) that's worked out really well despite the lack of control points in the bottom (choppy seas) and top third (heavily overcast skies) of the images.  However, there is a small misalignment of some coastline between two of the images toward the centre of the panorama.  I'd add control points nearer the coastline if I could, but there is absolutely no detail this low in the images (except boats, which move).  I did try adding a pair of new control points between these two (fog edges, so risky), and re-optimized all images.  The reported errors were much larger than they had been originally, so I chose not to accept the optimization and preserve what I had.

Does anyone have any suggestions for how I should be aligning these two images after my initial panorama has been stitched, such that I don't have to start over?

Many thank,
Terry

[Terry Duell]

Hello Terry,

On Tue, 10 Feb 2015 06:40:51 +1100, tbransco <TFTAJL...@spammotel.com>
wrote:

The only general advice I can offer without seeing the detail of this
project, is to do your initial stitch then save your .pto file (File ->
Save as). You can then try to make improvements, saving a new version of
your .pto if any subsequent stitch is better.
If it all goes haywire, you can simply start out where you left your first
stitch by opening your first .pto (File -> New, File->Open, then select
the .pto).
If you are still unable to get a good stitch, you could consider making
your images and your initial .pto file available (via Dropbox or similar)
and someone here will try to provide help on the project.

Cheers,
--
Regards,
Terry Duell

[tbransco]

Thanks, Terry.

I've done the .pto renaming, as you suggested, but so far no luck with the minor realignment.  One of the costs of going hand-held, despite the close stitch elsewhere in my pano.  Once I fiddle with the cp's connecting the (slightly) misaligned images in my stitch, what would be the proper steps to prepare for the next stitch?  Here, I'm thinking mostly of how to re-optimize properly, without disturbing other image pairs.  Is it even possible?

Terry

[Terry Duell]

Hello Terry,

On Tue, 10 Feb 2015 11:06:13 +1100, tbransco <TFTAJL...@spammotel.com>
wrote:

Altering control points and re-optimising will always have an effect on
the overall fit.
I guess the hope is that you can make an improvement where needed without
the fit elsewhere becoming noticeably bad.
One approach you might try when having this problem, is to only work with
a minimal set of images, optimise, then add the next image, re-optimise
and so on. Not sure if it would work with your case without seeing the
project. Parallax errors, which may be the cause of your problem, are
always hard to correct.
You can select which images hugin is to optimise or add control points to,
by selecting/de-selecting images in the Fast Panorama preview window.
I have had a quick hunt around to see if I have a project similar to what
you describe, to check how the above does actually work, but thus far
haven't found anything suitable to use as a test case...so I may be giving
you crook advice. Apologies in advanced if that is the case.

[bugbear]

Terry Duell wrote:
> Parallax errors, which may be the cause of your problem, are always hard to correct.

In general (when parallex is an issue), I try to create control
points far from the camera (which won't show parallax)

When I have a preliminary stitch I may try to add near-field
CPs, but (obviously) these cannot be perfect when genuine
parallex errors are present.

BugBear

[AlainC]

Le lundi 9 février 2015 20:40:51 UTC+1, tbransco a écrit :

However, there is a small misalignment of some coastline between two of the images toward the centre of the panorama.  I'd add control points nearer the coastline if I could, but there is absolutely no detail this low in the images (except boats, which move).  I did try adding a pair of new control points between these two (fog edges, so risky), and re-optimized all images. 

 

Usually I solve that problem by adding some horizontal lines control point on the coast line.

[tbransco]

Thanks for all the good advice, folks.  I did get the slight misalignment sorted out by adding a pair of CPs to the problem pair of images and re-optimizing the entire project.  I guess the fact my subject was no closer than about 8 km. made it possible for me to select CPs along the edge of a fog bank in the lower third of the image where the misalignment was most evident.  Parallax was also not an issue given the distance of my subject.

The end result, for anyone that's interested, is on my Flickr page:

https://www.flickr.com/photos/relentless_pickle/16297543610/