Align a stack of photos

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There are occasions where it is necessary to align a set of otherwise identical pictures:

  • Aligning red, green and blue channels to correct chromatic aberration.
  • Aligning photos taken over a period of time to create a time-lapse movie.
  • Aligning bracketed shots to create a single HDR or contrast blended image.
  • Aligning photos taken at different focus distances to merge into a single extended Depth of Field image.

Panorama tools is particularly useful for this process since it allows sub-pixel alignment and has a sophisticated lens correction model for applying distortion - Even photos taken years apart with different cameras can be aligned perfectly.

Most tools for HDR generation such as photomatix have some level of automatic alignment, so this may be sufficient for most purposes. Otherwise the hdrprep perl script automates the process described below:

Aligning with hugin

  • Start up a new hugin project for each series and load the images. Set the Field of View, lens parameters and projection type, ie. if your lens is a fisheye, set this for both the input and output projection.
  • Create control points via the Images tab. Panomatic may give better results than Cpfind.
  • Select "Positions and View (y,p,r,v)" and "Optimise now!" in the Optimise tab.
  • If necessary, fine tune the control points in the Control Points tab.
  • In the fast panorama preview, the images will be on top of each other. Select "Move/Drag" and "Fit", then deselect all images except the first. Select "Crop" and "Auto-Crop".
  • Deselect the first image and select the second image. Crop manually by only reducing the size of the crop rectangle. Continue one by one until the crop rectangle has been adjusted for all the images.
  • Select all the images again.
  • In the Stitcher tab, select "Calculate Optimal Size", then deselect the default panorama outputs and select "No exposure correction, low dynamic range" in the "Remapped images" section. Select "Stitch!".

See a more detailed view of this article here.