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Fixing distortion in stitched panorama

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Mickey64564

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I just put together a 20 image stitch of an interior shot as a test of PTAssembler's stitcher. Took me a while to get everything stitched up nice and smooth, but I'm not too happy with the wide angle distortion. I think the FOV is about 130 degrees but I'm wondering if there would be a way to correct for this, or is anything at this wide FOV gonna look this bad? Should I do something differently in the stitching process, or is there something I can do in post-processing? I tried the PanoTools Correct/Radial Shift filter in Photoshop, but couldn't get that to work properly. Any tips would be appreciated.

This was shot from a tripod at a fairly low angle which may account for the amount of distortion in the upper half of the image.



Michael

P.S. The resultant 35 megapixel image looks great other than the distortion. :)

--
http://www.pbase.com/mooremwm
http://www.photosig.com/userphotos.php?id=7178
 
Mickey said:
I just put together a 20 image stitch of an interior shot as a test
of PTAssembler's stitcher. Took me a while to get everything
stitched up nice and smooth, but I'm not too happy with the wide
angle distortion. I think the FOV is about 130 degrees but I'm
wondering if there would be a way to correct for this, or is
anything at this wide FOV gonna look this bad? Should I do
something differently in the stitching process, or is there
something I can do in post-processing? I tried the PanoTools
Correct/Radial Shift filter in Photoshop, but couldn't get that to
work properly. Any tips would be appreciated.

This was shot from a tripod at a fairly low angle which may account
for the amount of distortion in the upper half of the image.



Michael

P.S. The resultant 35 megapixel image looks great other than the
distortion. :)

--
http://www.pbase.com/mooremwm
http://www.photosig.com/userphotos.php?id=7178
Click to expand...
--
===================
http://www.Canon-Digital.com
===================
D60, 28-70L, 100-400L IS, 1GB IBM MD, Slick Pro 330DX, TC-80N3...
 
Hi Mickey - you might want to try using the PanoTools 'remap' plugin in Photoshop - choose convert from: 'QTVR panoramic' to 'normal' and enter the HOV (130 degrees) that was calculated. You may need to increase the canvas size prior to doing this - else you'll lose part of your image off the edges!

That should give you straight lines once more - it'll look as though taken with a rectilinear ultrawide lens - the penalty will be the apparent stretching of objects near the frame edges... i tend to decide on an image by image basis which type of projection looks more natural.
Hope that this helps some, john
 
Here are 2 samples (9 stitched pictures, the final picture is 8600 x 3300) I made today:

Before Andromeda LensDoc:



After Andromeda LensDoc:



You can also correct the perspective and rotation with this tool.

I hope this helps you...

Best regards,
Rudi.

--
===================
http://www.Canon-Digital.com
===================
 
Thanks John. I gave remap a shot and could almost get the balcony part straightened out, but when I did the rest of the image was severely distorted. I tried a number of different projection types and FOV values but couldn't get any of them to look any better. LOL, also when I tried increasing the canvas the slightest bit then running Remap, I got "out of RAM" errors (even with 512MB of RAM). Guess I'll just have to live with the distortion. ;) Maybe this sort of distortion is to be expected for such a wide FOV. I'm working on a new one today of the exterior of the home but I stepped back so that the entire pano would fit in a normal FOV then zoomed in to 102mm to take the shots. So far, it looks like I've got the right idea now. :)

Thanks for your suggestion,

Michael
John Davies said:
Hi Mickey - you might want to try using the PanoTools 'remap'
plugin in Photoshop - choose convert from: 'QTVR panoramic' to
'normal' and enter the HOV (130 degrees) that was calculated. You
may need to increase the canvas size prior to doing this - else
you'll lose part of your image off the edges!
That should give you straight lines once more - it'll look as
though taken with a rectilinear ultrawide lens - the penalty will
be the apparent stretching of objects near the frame edges... i
tend to decide on an image by image basis which type of projection
looks more natural.
Hope that this helps some, john
Click to expand...
--
http://www.pbase.com/mooremwm
http://www.photosig.com/userphotos.php?id=7178
 
Heh heh, thanks Maurice. Hmmm, I wonder how much they pay? :)

Yeah, I'm quite happy with how the stitching turned out...a little work in Photoshop and you can hardly notice any seems. Just that the curvature of the balcony would not be favoured by the builder who might not understand wide angle barrel distortion. ;)

Michael
Maurice Daniels said:
Nice job. NASA should hire you... their stiches are awful.... 8D
Click to expand...
--
http://www.pbase.com/mooremwm
http://www.photosig.com/userphotos.php?id=7178
 
I'm the author of PTAssembler. It looks to me like you used "cylindrical" projection for this image. This will give you curved horizontal lines above and below the horizon...(Notice how all the vertical lines are perfectly straight?) Try "rectilinear" projection to get straight horizontal lines. However, the larger the field of view, the more stretched the image becomes at the edges. At 130 degrees, the edges will look quite stretched...just like when using an ultra wide angle lens.

By the way, this has nothing to do with lens "distortion". It is simply a result of the output projection type.

Max
Mickey said:
I just put together a 20 image stitch of an interior shot as a test
of PTAssembler's stitcher. Took me a while to get everything
stitched up nice and smooth, but I'm not too happy with the wide
angle distortion. I think the FOV is about 130 degrees but I'm
wondering if there would be a way to correct for this, or is
anything at this wide FOV gonna look this bad? Should I do
something differently in the stitching process, or is there
something I can do in post-processing? I tried the PanoTools
Correct/Radial Shift filter in Photoshop, but couldn't get that to
work properly. Any tips would be appreciated.

This was shot from a tripod at a fairly low angle which may account
for the amount of distortion in the upper half of the image.



Michael

P.S. The resultant 35 megapixel image looks great other than the
distortion. :)

--
http://www.pbase.com/mooremwm
http://www.photosig.com/userphotos.php?id=7178
Click to expand...
 
Yep, you got it! BTW, thanks for the great app!

I figured this out just before I left for (Canadian) Thanksgiving dinner and had the stitch render while I was out. When I got back I saw the results and it looks much better after using the rectilinear projection rather than cylindrical. :)

The only problem is that the top left image sticks out to the left about 50% more than the other images in that column and as a result gets stretched severely and consequently reduces the size of the rest of the stitch like so:



I tried cropping the upper left image in half to better line up with the rest of the images on the left side but then it wouldn't stitch well (because of different proportions?). Is there some other way I could fix this, or should I just increase the output size dramatically then crop out the excess distorted corner and blank space? I guess I know why PTgui has a crop tool built in now...

Michael
Max Lyons said:
By the way, this has nothing to do with lens "distortion". It is
simply a result of the output projection type.

Max
Mickey said:
I just put together a 20 image stitch of an interior shot as a test
of PTAssembler's stitcher. Took me a while to get everything
stitched up nice and smooth, but I'm not too happy with the wide
angle distortion. I think the FOV is about 130 degrees but I'm
wondering if there would be a way to correct for this, or is
anything at this wide FOV gonna look this bad? Should I do
something differently in the stitching process, or is there
something I can do in post-processing? I tried the PanoTools
Correct/Radial Shift filter in Photoshop, but couldn't get that to
work properly. Any tips would be appreciated.

This was shot from a tripod at a fairly low angle which may account
for the amount of distortion in the upper half of the image.



Michael

P.S. The resultant 35 megapixel image looks great other than the
distortion. :)

--
http://www.pbase.com/mooremwm
http://www.photosig.com/userphotos.php?id=7178
Click to expand...
Click to expand...
--
http://www.pbase.com/mooremwm
http://www.photosig.com/userphotos.php?id=7178
 
This has happened because you captured more of the scene on the top left...My recommendation would be to increase the final stitch size and/or redce the horizontal FOV (equivalent to cropping the output image).

Max
Mickey said:
I figured this out just before I left for (Canadian) Thanksgiving
dinner and had the stitch render while I was out. When I got back
I saw the results and it looks much better after using the
rectilinear projection rather than cylindrical. :)

The only problem is that the top left image sticks out to the left
about 50% more than the other images in that column and as a result
gets stretched severely and consequently reduces the size of the
rest of the stitch like so:



I tried cropping the upper left image in half to better line up
with the rest of the images on the left side but then it wouldn't
stitch well (because of different proportions?). Is there some
other way I could fix this, or should I just increase the output
size dramatically then crop out the excess distorted corner and
blank space? I guess I know why PTgui has a crop tool built in
now...

Michael
Max Lyons said:
By the way, this has nothing to do with lens "distortion". It is
simply a result of the output projection type.

Max
Mickey said:
I just put together a 20 image stitch of an interior shot as a test
of PTAssembler's stitcher. Took me a while to get everything
stitched up nice and smooth, but I'm not too happy with the wide
angle distortion. I think the FOV is about 130 degrees but I'm
wondering if there would be a way to correct for this, or is
anything at this wide FOV gonna look this bad? Should I do
something differently in the stitching process, or is there
something I can do in post-processing? I tried the PanoTools
Correct/Radial Shift filter in Photoshop, but couldn't get that to
work properly. Any tips would be appreciated.

This was shot from a tripod at a fairly low angle which may account
for the amount of distortion in the upper half of the image.



Michael

P.S. The resultant 35 megapixel image looks great other than the
distortion. :)

--
http://www.pbase.com/mooremwm
http://www.photosig.com/userphotos.php?id=7178
Click to expand...
Click to expand...
--
http://www.pbase.com/mooremwm
http://www.photosig.com/userphotos.php?id=7178
Click to expand...
 
Yes, I think I've learned a good lesson here. I wasn't paying attention to FOV when I shot that interior series but from now on I will try framing the shot at wide angle and make sure the telephoto series doesn't extend too far past the FOV of my lens at 34mm or 25mm.

Thanks everyone for your help. I'll be back with samples when I get the interior and exterior stitches finished. :)

Michael
Thomas Niemann said:
Ultra wide-angle lenses seldom go over 90 degrees for FOV. Beyond
that, they're usually of the fisheye variety. If I go much over
that for a rectilinear image distortion becomes objectionable.

--
Thomas Niemann
http://epaperpress.com
Click to expand...
--
http://www.pbase.com/mooremwm
http://www.photosig.com/userphotos.php?id=7178
 
Thanks for the samples Rudi. The PanoTools plugin for Photoshop does this sort of thing as well but I needed something more drastic for the image I was working on due to the very large FOV. I've determined that I used a wrong setting in PTAssembler for the projection type and that fixed things up.

Michael
Vitam C++ said:
Here are 2 samples (9 stitched pictures, the final picture is 8600
x 3300) I made today:

Before Andromeda LensDoc:



After Andromeda LensDoc:



You can also correct the perspective and rotation with this tool.

I hope this helps you...

Best regards,
Rudi.

--
===================
http://www.Canon-Digital.com
===================
Click to expand...
--
http://www.pbase.com/mooremwm
http://www.photosig.com/userphotos.php?id=7178
 
Woohoo, I got the external stitch to work very well! No distortion that I can see and notta seam in sight. :) Only problem is I wasn't paying enough attention to the actual content when shooting and adjusted the polarizer only for the sky rather than the more important relections off the building. Oh well, the amount of detail is really unbelieveable...22.5MP of high-res goodness. :)

Here's a sample including a 100% crop:



Here's the rectilinear version of the interior stitch. Much less distortion and curvature of the balcony:



Still looks weird because of the very wide FOV though.

Michael

--
http://www.pbase.com/mooremwm
http://www.photosig.com/userphotos.php?id=7178
 
Here's a better shot of the exterior:



I could only shoot 10 frames for this angle because I was limited to a 102mm lens and I still had to crop it quite a bit. The resultant image is 14.3MP. I also shot it with a 2x teleconverter to get a total of 27 frames, so I look forward to stitching that together when I have more time. :)

Michael

--
http://www.pbase.com/mooremwm
http://www.photosig.com/userphotos.php?id=7178
 
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