Basic newbie question

[Daniel Md]

I am trying to merge 5 photos to make a wide(r) angle photo. Photos, .pto, and result are here 

As shown in annotated result there are discontinuities in the merged photo. I tried adding extra control points to help with the merge, but that was unsuccessful. How do I fix this kind of error? I'd like to understand how to correct similar errors in future projects.

Thanks

[Gunter Königsmann]

To me it looks like the camera hasn't only changed the angle it shot the images from, but also was moved horizontally, which means that one cannot warp the images in a way that they fit together in all places at once. Often Hugin Manages to move these discontinuities to places where they are hard to see.  But that often requires the images to overlap strongly in order to give hugin more possibilities to place the seams.

One important thing I had to learn was not to tilt the camera around its center, but around the center of the lens.

Kind regards, Gunter

[David W. Jones]

I don't do what Gunter recommends (rotate around the center of the lens,
also called the nodal point). There are ways to figure out where the
nodal point of your lens is, but I've never bothered since I use a zoom
lens and the nodal point changes based on focal length.

I rotate around my torso - set my feet stably, turn upper body to left
(or right, whichever you prefer), then shoot pictures with 50% overlap.
So the right edge of the first frame falls in the middle of the
viewfinder when I shoot the subsequent frame. Don't move the feet!

When shooting the higher row of images, frame that for a 50% overlap
between the bottom of the new frame and the corresponding image in the
lower row.

Also, keep the camera leveled horizontally. That helps keep things straight.

A last idea, if you can go back and reshoot it, is to shoot portrait
instead of landscape orientation. That might enable you to get the
entire center part of the panorama (house and that lovely little water
channel feeding into the pond) in one vertical shot. That would fix the
mismatched point in the water channel, and possibly eliminate the little
mismatch in the eve of the house. It might also trigger mismatches in
the lines of the pond, but I think Hugin would handle those better than
the existing mismatches.

Nice picture, that is a really lovely house and yard!

--
David W. Jones
gnome...@gmail.com
wandering the landscape of god
http://dancingtreefrog.com
My password is the last 8 digits of π.

[Sean Greenslade]

On Tue, Aug 08, 2023 at 07:27:17AM +0200, Gunter Königsmann wrote:
> To me it looks like the camera hasn't only changed the angle it shot the images from, but also was moved horizontally, which means that one cannot warp the images in a way that they fit together in all places at once. Often Hugin Manages to move these discontinuities to places where they are hard to see. But that often requires the images to overlap strongly in order to give hugin more possibilities to place the seams.
>
> One important thing I had to learn was not to tilt the camera around its center, but around the center of the lens.

I'm inclined to agree with Gunter, it looks like there's some
perspective warping between the photos. It would be best to try and
re-shoot with proper nodal rotation.

That said, you can somewhat recover from these sorts of issues with an
aggressive application of masks to force the seams into less noticeable
spots. The grass is a perfect candidate for this. I took a quick stab at
your pto, check out the results:

https://seangreenslade.com/tmp/2023-08-07/newt.pto

https://seangreenslade.com/tmp/2023-08-07/newt.jpg

--Sean

[RizThon]

As Gunter said, to avoid having those issues, you must be careful when taking the pictures.

The best thing is to have a tripod, and be able to keep the center of the lens at the same place between each shot. With handheld shots, try to rotate around the camera, instead of rotating the camera around you.

For your current pictures, it seems pictures IMPG9882.JPG and IMPG9883.JPG couldn't be mixed/fused properly. You could try to add a mask on one of those pictures, to force Hugin to use data of a single picture (see Hugin tutorial — Blend masks). For ex you add an include mask on IMPG9883.JPG along the path and up to the house. Note that you'll probably still have issues in other places, but if it's in the grass or trees, it may be less visible.

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[Daniel Md]

Thanks all for your advice. Unfortunately I am on a tour and we have been and gone. I shall try to keep these lessons in mind for future projects.

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[Daniel Md]

Thanks Sean, that looks quite good. I examined the masks and it seems to me the philosophy you used was to segregate out areas of strong lines (where discontinuities are easily caught by the eye) to single photos. Is this correct?

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[RizThon]

I usually use a mask if I find a visible discontinuity like you have. The problem is that it's quite trial and error. If you're lucky, then the new panorama will look good. If not, you may realize there's a new visible discontinuity somewhere else! In your case, there's grass next to the path, so a discontinuity there will not be as obvious. The house may cause more issues. So I guess you just need to try and see what you get.

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[Sean Greenslade]

On Tue, Aug 08, 2023 at 04:53:41PM -0400, Daniel Md wrote:
> Thanks Sean, that looks quite good. I examined the masks and it seems to me
> the philosophy you used was to segregate out areas of strong lines (where
> discontinuities are easily caught by the eye) to single photos. Is this
> correct?

Yes. In a situation like this where there are unavoidable
discontinuities, my main goal is to find photos where important /
high-detail features are fully visible in a single photo. In this case,
the house was fully in one shot and only partly in another, so I
exclude-masked the partial shot to make sure that the house will all
come from the same photo. In the same vein, I chopped the trees and much
of the water channel out of the three lower shots to make sure those
elements all came from one shot. Enblend does a good job of hiding the
seams in the grass.

In some situations, I've taken this technique a step farther by adding
the same photo into a pano twice, each with a different set of control
points focused on a different area. This can allow the different areas
of the image to warp differently, which can't happen with all the
control points on a single image. That could potentially help with the
pond in the foreground, since it's too big to have fit all into one
photo.

--Sean