Laszlo
Posts: 39
Location: Peabody, United States
Registered: 29 Feb 2008
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zenit and nadir brings error
Posted: 28 Jun 2009 at 21:28 GMT
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Hi,
is there any particular reason why the Nadir or/and Zenit shot gives me errors?
I shot 6 around tilted down 10 deg, one up tilted at 60deg and one down at -90 deg.
When I optimize in PTgui the 6 shots around I got "very good" average 1.6 control point distance error when I add the nadir and/or zenith I jump into the the "good" area, somewhere around 4 average.
Thanks
Laszlo
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John Houghton
Posts: 3019
Location: Hitchin, United Kingdom
Registered: 17 Jan 2005
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Re: zenit and nadir brings error
Posted: 29 Jun 2009 at 6:47 GMT
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Things that affect the alignment are
1. Panohead setup. You need to avoid vertical as well as horizontal parallax shifts.
2. Pay attention to the maximum cp distance error reported. Check and correct or delete the worst points as appropriate.
3. Optimize the horizontal and vertical lens shift parameters as well as a,b and possibly c as well.
4. Check that the nadir and zenith are in the correct orientation. All images should be rotated from the native landscape orientation of the camera by the same angle. E.g. all at -90 degrees. When generating tiff from RAW in ACR, the orientation can be displayed in the metadata panel.
John
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DorinDXN
Posts: 2408
Location: Timisoara, Romania
Registered: 14 Nov 2006
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Re: zenit and nadir brings error
Posted: 29 Jun 2009 at 7:13 GMT
updated: 29 Jun 2009 at 7:14 GMT
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I would add that PtGui can tell you "very good" but the meanning of that deppends on where the control points are, especially when you optimize lens parametter and FOV, if the points are clustered on the middle, you can have "very good" result but you might have visible stitching errors on the top and botom.
Dorin
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Laszlo
Posts: 39
Location: Peabody, United States
Registered: 29 Feb 2008
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Re: zenit and nadir brings error
Posted: 30 Jun 2009 at 23:47 GMT
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Than you guys.
For sure, I will have to start/continue with my panohead setup. John, I was following your tutorial with tape on the window. I stitched the photos, I had CP only on background, but in PS when I was overlapping the layers the tape does not move but the background does.Did I missed something?
I use a Tokina 10-17 fisheye so I belive this also influences the setup...fisheye does not not have a exact point for the NP, as you describe in your tutorial.
Yes I delete those worst points with high avg. error, still I am not where I want to be.
the optimization of hor and vert shift helped. CP distances min/avg/max =0.1/1.4/5.8 I never got so low.
Orientation of images is all over the place. Roll parameter Image 1 - 5 varies from -0.0788 to -1.2 Zenit is at -93.9 Nadir -148. I keep overwriting but it jumps back after optimization.
Anyway the result is much better. I will post the image in the gallery so you can take a look.
Thanks guys
Laszlo
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DennisS
Posts: 660
Location: Los Anglels, United States
Registered: 1 Sep 2007
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Re: zenit and nadir brings error
Posted: 1 Jul 2009 at 1:13 GMT
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Neither the backgroud nor the tape should move when you finally get the camera in the right position.
If you do not have any stitching errors in your final panorama, don't worry about the numbers PTGui is giving you. If you are introducing stitching errors when you add in the Zenith and Nadar, it would appear you do not quite have the correct camera position.
I am finally getting "too good to be true" in PTGui after doing a lot of calibration. Be patient and follow all the tutorials you can find on camera positioning. 1mm can make a difference. Side to side is as important as front to back on the pano head. Once you nail it down, you should see the average error easily fall below 2.
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John Houghton
Posts: 3019
Location: Hitchin, United Kingdom
Registered: 17 Jan 2005
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Re: zenit and nadir brings error
Posted: 1 Jul 2009 at 6:40 GMT
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Laszlo said: I stitched the photos, I had CP only on background, but in PS when I was overlapping the layers the tape does not move but the background does.Did I missed something?
For a quick stitch of the two images, assign the best values you have previously obtained for the lens parameters. Then only optimize only y,p,r for one image. With cp's only on the background and an optimization average distance of around 1, the background should align very well in Photoshop.
Orientation of images is all over the place. Roll parameter Image 1 - 5 varies from -0.0788 to -1.2 Zenit is at -93.9 Nadir -148. I keep overwriting but it jumps back after optimization.
If you set y=p=r=0 degrees for image 0, and don't include these parameters in the optimization, the panorama as a whole will be kept in a more-or-less level state. It can be properly levelled at the finish using t1 and t2 points. Ignore variations in roll parameters. If you are getting a reasonable optimization and the image generally looks ok with nothing grossly out of place, there is nothing to worry about. For a zenith or nadir image, variations in roll and yaw values have similar effects.
One thing not mentioned before that you might check for: make sure that control points are assigned only on neighboring images, i.e. between 0/1, 1/2, 2/3 etc. on the horizontal row. Delete any points between 0/2, 1/3 etc. that might have been assigned automatically.
John
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