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Old Sep 25, 2005, 7:25 PM   #1
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I am trying to build a panoramic view that consists of about five pictures. They were taken using a tripod. Stitching the first three left-to-right came out with acceptable results. However the fourth shows a horrendous perspective difference that would make a straight street visible in the shot (which would show as a nice arch) with a sharp change in angle at the curb. Here are the two parts. First is the leftmost three shots stitched and then the next image. I know this is caused by vignetting in the camera lens at its wide angle setting. This is a consumer camera with little manual controls.

I have seen some tutorials on the Internet about panoramic pictures and some use vertical images. Will taking the same scene using vertical images will minimize this problem?





I am hosting them elsewhere due to the width of the first image.
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Old Sep 25, 2005, 7:32 PM   #2
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Just some more details to clarify why the entire scene does not look horizontal. This location, including the street and the town square at the other side of the street has a gentle slope with the left side being the highest point. I later noticed that the tripod was not perfectly vertical either. The slope adds way more to the effect than the tripod non-vertical position.
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Old Sep 25, 2005, 8:16 PM   #3
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As you mentioned you are using a tripod to hold the camera steady and level the shot.
That is an important good start.
Both the tripod, and the camera need to be leveled seperately.

Other things to consider are:
  • If there are near objects in the images you need to rotate the camera around the lenses nodel point. Which is probably not at the cameras tripod mount.The nodel point is the place where the lens brings the image to focus. [/*]
  • Using 3 verticals with about a 1/3 overlab lets you build an image with an aspect ratio similar to a normal image from a much larger megapixel camera.[/*]
  • The lens you pick to make the images for the panorama needs to be rectilinear. A lens with a very short real focal length will distort each of the images making stitching tough.
    [/*]
Grab a copy of the easy to use autostitch and give it a whirl.
http://www.cs.ubc.ca/~mbrown/autostitch/autostitch.html

Peter.
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Old Sep 25, 2005, 8:39 PM   #4
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Does your software allow inputing roll and pitch? Or calculate it from points that you specify?

Does it allow output as a rectilinear projection, or just cylindrical? In any case, if the angle of view is more than about 120 degrees (doesn't seem to be), a rectilinear projection is not possible.

Shooting vertical will not do a thing for the perspective distortion so long as you keep a cylindrical projection.

In short, I think you basic problem is software limitations.

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Old Sep 25, 2005, 9:41 PM   #5
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The software is very limited in this tool. I only specify one reference point and the amount of blurriness so to speak in the overlap. It is ArcSoft Photo Studio which came with my scanner.

I know it is not possible to obtain a rectilinear projection given the depth of of the pictures - the street curb is relatively close to me and there are distant objects and buildings. However it puzzles me the sharp change in the perspective between the third and fourth pictures.

The idea of going vertical is to get farther away from the corners of the picture where vignetting is more apparent.

style="BACKGROUND-COLOR: #000000"Or maybe if I overlap more between pictures.
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Old Sep 25, 2005, 9:43 PM   #6
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PeterP wrote:
Quote:
As you mentioned you are using a tripod to hold the camera steady and level the shot.
That is an important good start.
Both the tripod, and the camera need to be leveled seperately.

Other things to consider are:
  • Peter.
  • Probably that was my mistake in the leveling part. The tripod was level according to the little bubble indicator but it is very possible that the camera itself was slightly off.

    I am starting to think that both my camera and my software are not up to the kind of panorama I want to make. The perspective itself is quite complex.
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Old Sep 25, 2005, 10:07 PM   #7
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Sounds like you could also use some more software :G
The above mentioned autostitch is free, and very easy to use, almost completely automated. When it works, it works great, if it runs into trouble you are out of luck.

A much more powerfull package is Panorama Tools also free.
http://www.path.unimelb.edu.au/~dersch/ but not very easy to use.
There are a lot of GUI front ends that have been released for it.

I tried the demo of realwiz a very expensive package and did not like it at all.
It made a mess out of simple images autostitch did not have any trouble with.

Peter.
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Old Sep 26, 2005, 4:01 PM   #8
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Panorama Tools still seems to be the gold standard for stitching. I never figured out how to use it in its native mode, but with PTGui as a graphic front-end it isn't to bad. One of the other graphic front-ends might be as good (haven't checked): like PTAssmbler, Hugin, PTMac, and several others.

Luisr - if you put the five individual shots up, I'll take a shot as stitching them. Keep them small, I have a dial-up connection.
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Old Oct 14, 2005, 7:22 PM   #9
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Hi there! I haven't visited againlooking for a moment to shoot again the panoramic shot I am trying to build but the weather has not cooperated for the last two weeks. Maybe this weekend the sun will be out again with blue skies.

Bill, grab the pictures from here: http://www.juanadiaz.org/fotos

They have been reduced to 1024x683 to make it friendlier to your connection.
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Old Oct 15, 2005, 7:49 AM   #10
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luisr & BillDrew,

Have been following this thread and here is a very quick uncropped stitch using autostitch which is one of the easiest to use. You can find it here http://www.cs.ubc.ca/~mbrown/autostitch/autostitch.html

Bill/
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