Luminance HDR can optionally use align_image_stack command line tool bundled with Hugin, a panorama stitcher, for the alignment of slightly misaligned images. When several differently exposed images are taken in the process of creating a High Dynamic Range image, the images are not perfectly aligned, and the quality of the HDR image created will suffer from this. align_image_stack uses the tools available to Hugin to optimize the roll, pitch and yaw, as well as some parameters of the lens geometry, to align the images.
align_image_stack doesn’t have a lot of relevant options, so we list them here:
|-a prefix||Output aligned images as prefix_xxxx.tif|
|-e||Assume input images are full frame fish eye (default: rectilinear)|
|-t num||Remove all control points with an error higher than num pixels (default: 3)|
|-f HFOV||Approximate horizontal field of view of input images, use if EXIF info not complete|
|-m||Optimize field of view for all images, except for first. Useful for aligning focus stacks with slightly different magnification.|
|-c num||Number of control points (per grid) to create between adjacent images (default: 8)|
|-l||Assume linear input files|
|-s scale||Scale down image by 2^scale (default: 1 [2x down-sampling])|
|-g gsize||Break image into a rectangular grid (gsize x gsize) and attempt to find num control points in each section (default: 5 [5x5 grid])|
|-v||Verbose, print progress messages. Repeat for higher verbosity|
By default Luminance HDR just defines the option for verbose printing -v.