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In March 2011 I tried in vain to align 3 images with Hugin so that I could compare them with mouseover image manipulation (run the mouse cursor over the images below to see what this means).. The main problem was that one of the images was taken at a different focal length, so they didn't line up. I asked on the Hugin mailing list, but didn't get the answers I wanted. In February 2013 I finally worked it out—I thought. Since then I've discovered a number of cases where this method didn't work, and I'm still trying to work out when it does and when it doesn't. Read on and try it; feedback more than welcome.

Here's what you need to do, based on the images I took 2 years before. Run the mouse cursor over the images to compare with the following image, or click on the images for larger versions:


This should be Verandah-before-orig.jpeg.  Is it missing?
Image title: Verandah before orig          Dimensions:          4032 x 3024, 2400 kB
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All images taken on Wednesday, 30 March 2011, thumbnails          All images taken on Wednesday, 30 March 2011, small
Diary entry for Wednesday, 30 March 2011 Complete exposure details

 
This should be Verandah-during-orig.jpeg.  Is it missing?
Image title: Verandah during orig          Dimensions:          4032 x 3024, 2432 kB
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All images taken on Wednesday, 30 March 2011, thumbnails          All images taken on Wednesday, 30 March 2011, small
Diary entry for Wednesday, 30 March 2011 Complete exposure details

 
This should be Verandah-after-orig.jpeg.  Is it missing?
Image title: Verandah after orig          Dimensions:          4032 x 3024, 2480 kB
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All images taken on Wednesday, 30 March 2011, thumbnails          All images taken on Wednesday, 30 March 2011, small
Diary entry for Wednesday, 30 March 2011 Complete exposure details

 

In this article, all images are shown in relatively small format. Click on an image up to 3 times to enlarge it.

The steps are:

  1. Load the images into Hugin, of course.

  2. In the Images tab, select Create control points. Depending on the images, CPfind or panomatic is better. In this particular example, CPFind did not find any control points between the middle image and the other two.


    This should be Hugin-1.gif.  Is it missing?
    Image title: Hugin 1          Dimensions:          1920 x 1080, 70 kB
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    All images taken on Sunday, 10 February 2013, thumbnails          All images taken on Sunday, 10 February 2013, small
    Diary entry for Sunday, 10 February 2013

       
    This should be Hugin-1-detail.gif.  Is it missing?
    Image title: Hugin 1 detail
    Dimensions: 719 x 147, 8 kB
    Dimensions of original: 719 x 147, 8 kB
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  3. Check the results in the Control Points tab. If, as here, the images are of different sizes, the results will not be very good:


    This should be Hugin-2.gif.  Is it missing?
    Image title: Hugin 2          Dimensions:          1920 x 1080, 1120 kB
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    Diary entry for Sunday, 10 February 2013

     

    To confirm, press F3 to get the control point table, then select the head of the column Distance to see the control point errors in descending order:


    This should be Hugin-3.gif.  Is it missing?
    Image title: Hugin 3          Dimensions:          924 x 673, 36 kB
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    All images taken on Sunday, 10 February 2013, thumbnails          All images taken on Sunday, 10 February 2013, small
    Diary entry for Sunday, 10 February 2013

     
  4. Save the project file. If things go wrong in the next step, you can reload it and try again with other parameters.

  5. In the Optimiser tab, select Positions and View (y,p,r,v) and Optimise now!:

     
    This should be Hugin-5.gif.  Is it missing?
    Image title: Hugin 5
    Dimensions: 446 x 292, 24 kB
    Dimensions of original: 446 x 292, 24 kB
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    This should be Hugin-6.gif.  Is it missing?
    Image title: Hugin 6
    Dimensions: 405 x 232, 14 kB
    Dimensions of original: 405 x 232, 14 kB
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    If this works, as above, then all is well. But it seems that if the focal lengths are too close together, the optimizer fails, and you get a message like:

     
    This should be optimizer-fail.gif.  Is it missing?
    Image title: optimizer fail
    Dimensions: 475 x 256, 12 kB
    Dimensions of original: 475 x 256, 12 kB
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    If this happens, you can try selecting Positions (y, p, r), but in my experience this doesn't often work. I don't have a solution for this case.

    Another case where this doesn't work is if the images have been taken from a slightly different position. In this case, the selection Positions and Translation (y,p,r,x,y,z) might work. In general there's room for experimentation with various optimization parameters.

  6. In the first case, the images now line up well. If necessary, return to the Control Points tab and edit the worst control points.

  7. In the Fast Panorama Preview window, all the images will be on top of each other, and probably far too small:


    This should be Hugin-7.gif.  Is it missing?
    Image title: Hugin 7          Dimensions:          1920 x 1080, 134 kB
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    Diary entry for Sunday, 10 February 2013

     
  8. Select Move/Drag and Fit:


  9. This should be Hugin-8.gif.  Is it missing?
    Image title: Hugin 8          Dimensions:          1920 x 1080, 736 kB
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    Diary entry for Sunday, 10 February 2013

     
  10. To get the largest crop that fits all images, select Crop then HDR Autocrop:

  11.  
    This should be Hugin-13-detail.gif.  Is it missing?
    Image title: Hugin 13 detail
    Dimensions: 444 x 175, 12 kB
    Dimensions of original: 444 x 175, 12 kB
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    This should be Hugin-13.gif.  Is it missing?
    Image title: Hugin 13          Dimensions:          1331 x 1063, 688 kB
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    Diary entry for Sunday, 10 February 2013

     
  12. Move to the Stitcher tab. Select Calculate Optimal Size, deselect Panorama Outputs, and select No exposure correction, low dynamic range in the Remapped Images section, then Stitch!.


    This should be Hugin-12-detail.gif.  Is it missing?
    Image title: Hugin 12 detail          Dimensions:          851 x 833, 56 kB
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    The image names will be created from the base name you specify (here example) by appending _exposure_layers_ and a sequence number:

    ===========================================================================
    Stitching panorama
    ===========================================================================
    nona  -z LZW -r ldr -e 10.3056 -m TIFF_m -o example_exposure_layers_ -i 0 /var/tmp/huginpto_wEvx1A
    nona  -z LZW -r ldr -e 10.3056 -m TIFF_m -o example_exposure_layers_ -i 1 /var/tmp/huginpto_wEvx1A
    nona  -z LZW -r ldr -e 10.3056 -m TIFF_m -o example_exposure_layers_ -i 2 /var/tmp/huginpto_wEvx1A


    === grog@eureka (/dev/pts/7) ~/Photos/20110330 55 -> ls -l example*                    
    -rw-r--r--  1 grog  lemis  25264578 10 Feb 12:14 example_exposure_layers_0000.tif
    -rw-r--r--  1 grog  lemis  24988642 10 Feb 12:14 example_exposure_layers_0001.tif
    -rw-r--r--  1 grog  lemis  25387168 10 Feb 12:14 example_exposure_layers_0002.tif

Here the results, rearranged in time sequence. Run the mouse cursor over the images to compare with the following image, or click on the images for larger versions:


This should be Verandah-before.jpeg.  Is it missing?
Image title: Verandah before          Dimensions:          3810 x 2715, 2736 kB
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All images taken on Wednesday, 30 March 2011, thumbnails          All images taken on Wednesday, 30 March 2011, small
Diary entry for Wednesday, 30 March 2011 Complete exposure details

 
This should be Verandah-during.jpeg.  Is it missing?
Image title: Verandah during          Dimensions:          3810 x 2715, 2720 kB
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All images taken on Wednesday, 30 March 2011, thumbnails          All images taken on Wednesday, 30 March 2011, small
Diary entry for Wednesday, 30 March 2011 Complete exposure details

 
This should be Verandah-after.jpeg.  Is it missing?
Image title: Verandah after          Dimensions:          3810 x 2715, 2752 kB
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All images taken on Wednesday, 30 March 2011, thumbnails          All images taken on Wednesday, 30 March 2011, small
Diary entry for Wednesday, 30 March 2011 Complete exposure details

 

If you want to try this with these images, they're here, here and here. In total they're about 8 MB.

In passing, it's worth noting how little you can rely on the information in the EXIF data. According to that data, the first image was taken at a focal length of 23.0 mm, and the other two were taken at a focal length of 21.0 mm. Hugin reports focal lengths of 21.98972 and 21.45713. While these may not be absolutely accurate, the difference in focal length is probably close enough—only 0.5 mm instead of the 2 mm that the EXIF data suggests.


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