Panoramas on Linux

6 10 2008

Larger version: here

This shot is made up of 7 RAW shots from my Canon EOS 400D (aka Rebel XTi) w/ EF-S 17-85mm IS USM lens, here was the process I followed:

The shoot:

1. Mounted the camera on a tripod in portrait orientation, doing this has two benefits… firstly puts the barrel distortion introduced by your lens on the top and bottom making the shots easier to blend and stitch, also it’ll give your pano more height. The down side of course is that you’ll need to take more shots than you would with landscape to get the same field of view.

2. Put the camera in Manual mode to ensure that the exposure is locked. If you use any of the Auto/Semi-auto modes… your camera will re-meter for exposure for each shot – causing the brightness of each shot to differ.

3. Then I selected a specific white balance, in this case ‘daylight’ – but the important thing is not to have it on Auto White Balance, otherwise each shot is likely to be a different temperature.

4. Next I dialed in the aperture to a tiny (F/22), this is to ensure that I get the deepest Depth of Field (DoF) as possible so the foreground and background are sharp and in focus.

5. Then I used the auto focus to do the focus work for me, then once focus was achieved I switched to Manual Focus to ensure that each shot is taken with the same focus.

6. Finally, using my Canon IR remote I shot off the first shot then carefully panned by tripod head until there was approximately 20% overlap from the previous shot then shot off again… then continued until I had the complete field of view I was after.

The post processing:

I did the post processing on my Linux (Ubuntu) box, as a minimum you’ll need the following:

Here is the process I followed:

1. Converted my RAW images to JPEG using dcraw. I used a custom version of the script available here: http://jcornuz.wordpress.com/2008/07/10/here-is-a-little-something-for-your-blog/

2. Renamed the .JPEG output to .JPG, because Autopano-sift-C fails with .JPEG extensions.

3. Batch rotated JPEGs using mogrify from ImageMagick (mogrify -rotate “-90” *.JPG)

4. Opened images in Hugin, and got it to use Autopano-sift-C to automatically find the control points between the set of images.

5. Hugin then uses ‘nano’ to modify the geometry of the images, then ‘enblend’ to stitch them all together.

FYI – I did run into an issue with the latest CVS version of Enblend (v3.2), and had to downgrade to a previous version to make it work.

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