Stitching problem due to change in image sizes

[Andrew]

I recently created a spherical panoramic image that looked fine other
than what looked like a possible stitching problem. When I looked at
what images I had used I discovered that I accidentally included a few
images from a location a few feet away.

When I removed those images and re-ran them through PTGui I expected
that the panoramic would now be perfect. Instead, it no longer
stitches properly at all and things are jumbled up.

When I looked at the images to see what was going on I saw that a
handful of the images are now approximately half the size of the other
images. The width and height are about half and the generated thumb
nails images are half the size.

The original photos are located in Aperture files. It doesn't matter
if I drag the images into PTGui individually or as a group.

Does any know what is going on with my images?

[John Houghton]

Andrew, Possibly you have images in mixed orientations.  Check the
thumbnails on the Source Images tab: they should all be in portrait or
all in landscape orientation.  Otherwise, the only way you could have
different image sizes in the output panorama would be if you had
specified individual lens parameters on the Lens Details tab. If
neither of these applies, please supply a copy of the saved project
file for investigation. (Images not required).




John




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[Andrew]

Thank you John.

I'm not sure if there is an orientation issue or not. The photos I'm adding are all in the same orientation - portrait. The thumbnail images after I add them show them all in portrait orientation.

However, after I have PTGui align them, and the alignment "fails" , the thumbnail images are no longer all in the same orientation. Some are now in landscape orientation.

Is it possible that because I originally created the panorama with extra images that PTGui now expects the panorama created with this group of photos to have the extra images still. So, the program is trying to fit X number of images where it is expecting there to be Y number? Is there a retained image cache for this project that I need to delete?

Andrew

[Erik Krause]

Am 19.10.2012 15:35, schrieb Andrew:
> Is it possible that because I originally created the panorama with
> extra images that PTGui now expects the panorama created with this
> group of photos to have the extra images still. So, the program is
> trying to fit X number of images where it is expecting there to be Y
> number? Is there a retained image cache for this project that I need
> to delete?

If you started from scratch (without applying the last project as
template f.e.) there should be no such need.

Could it be you have your tripod head in the images? Sometimes PTGui
fails because it assigns control points on the panorama head. In that
case use the mask tool (pro version only) or alpha channel mask them
before stitching in a different application.

And as John wrote: please supply a copy of the saved project

file for investigation. (Images not required).

--
Erik Krause
http://www.erik-krause.de

[Andrew]

I will check that out.

Here's what's odd. I shot the same scene twice, same angle, but separated by about 50 feet. I have a group of 28 images for each location. I ran the images separately through PTGui for each group of shots and got 2 fine-looking panoramas. However, for one of the panoramas I saw what looked like radial artifacts - some kind of stitching errors. When I went back to see what images I had used I discovered I had accidentally included 8 photos from Location 1 with the images from Location 2.

Both groups of photos have nadir shots showing the tripod. But, I was able to get fine-looking panoramas for each location.

So, I started over with both groups of images. I expected the Location1 panorama would be basically unchanged since the 8 images I was returning to the mix were precautionary ones I had taken to make sure I had full coverage. I expected the Location 2 panorama to also be basically unchanged but would no longer have the subtle radial artifacts that were there before.

Much to my surprise the now "correct" group of images for each location no longer stitch properly.

[John Houghton]

On Oct 19, 2:35 pm, Andrew <alau...@pch.com> wrote:
> However, after I have PTGui align them, and the alignment "fails" , the thumbnail images are no longer all in the same orientation.  Some are now in landscape orientation.

Which thumbnail images are we now talking about? The ones on the
Source Images tab (the important ones) should not have changed. The
ones on the Project Assistant tab merely reflect the current
individual orientations in the output panorama.

John

[Erik Krause]

Am 19.10.2012 16:42, schrieb Andrew:
> Much to my surprise the now "correct" group of images for each location no longer stitch properly.

Please provide the project files for download somewhere!

[Andrew]

Here's a link. I'm not sure this is what you wanted to look at.
https://www.dropbox.com/sh/3ijoankt5j6z0uw/g3oYQpUa-y

I started from scratch again. This time I excluded my zenith and nadir shots. The images still didn't align entirely - 2 images were misplaced. Those 2 images were listed as having twice the width and height of the rest of the images in the file. That project file is attached.

When I removed those images things went perfectly.

Thank you for all of assistance with this. I'm still confused about why the error crept in once I took images from where they didn't belong and put them where they did.
Andrew

[John Houghton]

On Oct 19, 7:57 pm, Andrew <alau...@pch.com> wrote:
> I started from scratch again.   This time I excluded my zenith and nadir shots.
> The images still didn't align entirely - 2 images were misplaced.
> Those 2 images were listed as having twice the width and height of the rest
> of the images in the file.

Andrew, I'm confused.  I thought you were suspecting that PTGui was
changing some images sizes.  Test1 shows the presence of two rogue
images twice the size of the rest. No control points were generated
for these and so were misplaced.  You say you removed those two images
rather than replaced them with versions of the proper size for Test2.
 That meant you didn't have the three complete rows of eight as shot,
but the images did stitch ok.  But why so many images when most people
manage well enough with one third of that number?  And why are they in
such a haphazard order?  Clicking the Sort button on the Source Images
tab gives a sensible ordering.




John

[Andrew]

Hi John,
Here's a link to the second saved project. It generated a fine pamoramic as far as I can tell even with the uneven rows as you saw. I guess there was sufficient overlap without them so their absence made no difference. More on that below.

https://dl-web.dropbox.com/get/Test%20panos/Test%202.pts?w=1b6312bb

I have no idea why those 2 images are twice the size of the others. They are from the same sequence of photos as the others with no changes in settings. As I said, the sequence of images stitched fine before except for artifacts caused by my mistaken inclusion of images that were not part of this sequence.

I just started doing panoramic images. The first effort I made didn't stitch well because of my subject choice - lots of open sky above and a pond in the foreground. A lesson I took from this was that it made sense to shoot extra images to ensure sufficient coverage. For my next round of test panoramas I went with the following approach - 8 images around, 8 images shot up at a 45 degree angle, 8 images shot down at a 45 degree angle, 2 zenith images 180 degrees different, 2 nadir images 180 degrees different.

I have done at least 8 panoramics that way that have all turned out fine. The only problem I have had is with these 2 panoramas and only then when I moved the images that I had mistakenly included with one group and put them where they belonged with the other set of images.

I appreciate your assistance a lot and am looking forward to finding out the answer to this mystery.

Andrew

[Erik Krause]

Am 19.10.2012 20:57, schrieb Andrew:
> Here's a link. I'm not sure this is what you wanted to look at.
> https://www.dropbox.com/sh/3ijoankt5j6z0uw/g3oYQpUa-y

It looks like the images in those project files are no camera size
images but preview files. I'm not familiar with aperture, but from the
naming I'd suspect that those are smaller images than those originally
shot. Or would you shoot 853 x 1280 pixels for a panorama? Aperture
might have generated previews at different sizes.

If the original images are in JPEG format use them as loaded from the
camera. If they are raw files, convert them to TIFF 16 bit all with the
very same fixed settings. No auto-settings! You should end up with files
all having the same pixel size, same white balance and same exposure
(provided you didn't shoot brackets). PTGui should process those images
flawlessly.

[Erik Krause]

Am 20.10.2012 22:22, schrieb Erik Krause:
> PTGui should process those images flawlessly.

I should have added: if you remove the excessive images.

As John wrote, those are far too many. You get a less then optimal
stitch if you have that many images, at least if you don't delete the
control points between the non-adjacent pairs - which is a PITA for that
amount.

[Andrew]

Thank you Erik. The images that I brought in were JPEG images. The images I shoot are the highest quality JPEG image my Canon T2i shoots. If the images that are getting processed are Preview sized I don't know why that is happening. Any thoughts?

An unexpected benefit I found to using the amount of images I used was that the transition as I rotate around the panorama is very natural and smooth. I, and others who have looked at my panoramas, find them very immersive. Other panoramas we have seen look unnatural and distracting because of distortions in the view as we rotate around the panorama. I assume that is occurring because they use fewer images. But, I'm a newbie to doing panoramas and I appreciate your insights into how I can improve what I'm doing.

Thank you again,
Andrew

[John Houghton]

On Oct 21, 12:13 am, Andrew <alau...@pch.com> wrote:
> An unexpected  benefit I found to using the amount of images I used
> was that the transition as I rotate around the panorama is very
> natural and smooth.  I, and others who have looked at my panoramas,
> find them very immersive.  Other panoramas we have seen look unnatural
> and distracting because of distortions in the view as we rotate around
> the panorama.  I assume that is occurring because they use fewer
> images.

Andrew, This is a common misconception.  The type lens you use and
focal length makes no difference to the  general appearance of the
panorama.  The perspective distortions as you rotate the image will be
identical.  Of course the image quality will vary according to the
lens in terms of such things as colour aberrations, flare and
resolution, but the extreme distortions of a fisheye lens, for
example, do not somehow make their presence felt in the final stitched
image.  See this comparison showing panoramas shot with a standard
rectilinear lens and fisheye:

http://www.johnhpanos.com/comp-8-105s.jpg


Perspective distortions become more distracting with large angles of
view, so it's advisable to set a realistic limit on that when you
generate the interactive image.

John

[Erik Krause]

Am 21.10.2012 01:13, schrieb Andrew:

> The images I shoot are the highest quality JPEG image my Canon T2i shoots.

Then they should have a size of 5,184 � 3,456 pixels.

> Any thoughts?

Sorry, I have no experience with aperture at all. However, I'd try to
load the images directly from the file system using PTGui Load Images
button on Project Assistant tab.

As for the number of images: The problem is that if images overlap with
non-adjacent images (f.e. 1 and 3, 2 and 4 etc), PTGui will likely find
control points between those images. Those control points will usually
have larger deviations and hence spoil the over all alignment. The
reason are some optical (or rather: geometrical) properties of fisheye
lenses, not the inability of PTGui to do a good alignment, BTW.

[Andrew]

Thank you John. That was very informative. For this sequence of shots I used a Rokinon 8mm lens with my Canon T2i. How would you have shot that scene to generate a spherical pano?

I have a question about the images in the link you sent me. Why were 42 images used/needed to create the first pano?

Thank you again,
Andrew

[Andrew]

Thank you Erik. I will look more closely into what's going on with my images in Aperture and when I load them. FYI, Aperture is an Apple program that is similar to Lightroom.

I shot this scene with a Canon T2i using a Rokinon 8mm lens. How would you have shot this scene to produce a spherical pano?

Also, this lens does not provide EXIF data. When I ran the images through PTGui I indicated that I used a fisheye lens, that it is an 8mm lens, and that it is a fisheye that produces a rectangular not circular image. Did I set things up right? Is there anything else I need to do?

Thank you again,
Andrew

[Erik Krause]

Am 21.10.2012 15:34, schrieb Andrew:
> Also, this lens does not provide EXIF data. When I ran the images
> through PTGui I indicated that I used a fisheye lens, that it is an
> 8mm lens, and that it is a fisheye that produces a rectangular not
> circular image. Did I set things up right?

Yes, perfectly.

> Is there anything else I need to do?

You should perhaps optimize for "Heavy + Lens shift". To do so choose
Advanced interface on Project Assistant tab top right corner. Then you
should see Optimizer tab where you can select this under "Minimize lens
distortion". The Rokinon (which is a re-labeled Samyang) needs this,
since it has a pretty non-standard fisheye mapping.

[UtahBob]

On Sunday, October 21, 2012 9:34:23 AM UTC-4, Andrew wrote:

Thank you Erik.  I will look more closely into what's going on with my images in Aperture and when I load them.  

Andrew, It seems that you must have an export preset established with the dimensions of 1280 x 853 which seems more like a monitor dimension and I start to think perhaps you have cropped the image to your display aspect ratio and then exported it but I can't recreate that myself.   The two larger images that you had with dimensions of 2592 x 1728 look like 50% crops of full size canon t2i images.  I have a 50% export preset in my Aperture and I sometimes use that when I want to send out smaller images.  I am on Aperture 2 but I don't use it for image processing at all.  I use LR and PS for that work.

If you post your Aperture workflow we might be able to see where you are creating these smaller dimension files - I would look at those export presets.   Bob

[John Houghton]

On Oct 21, 2:21 pm, Andrew <alau...@pch.com> wrote:
> I have a question about the images in the link you sent me.  Why were 42 images used/needed to create the first pano?

Because of the narrow field of view of the 105mm lens, many more
images are needed to cover a given fov than are needed for a fisheye
lens. You would choose a long focus lens when you want a high
resolution image for printing purposes, for example. These two
panoramas were shot specifically for use in answers to questions along
similar lines that crop up regularly. I wanted to shoot the panoramas
with two very different lenses simply to demonstrate the fact that the
stitched results will look convincingly identical.

Recommended shooting configurations for various lenses can be found
at:

http://www.vrwave.com/panoramic-lens-database/

John

[Andrew]

Outstanding John! Thank you forall of your assistance. My panos will be much betterbecause of it.

Andrew

[Andrew]

Thank you Bob. I appreciate your insights about what I should check out in Aperture.

Andrew