Image-stacking (referred to in some texts as the shift-and-add
method) is a form of speckle imaging commonly used for obtaining high quality
images from a number of short exposures with varying image shifts. It has been
used in astronomy for several decades, and is the basis for the
image-stabilization feature on some cameras. It involves the calculation of
"motion vectors", which describe how a given scene has moved from one image to
another. The images are then shifted back to a common center and added together.
This provides an image with higher resolution (higher signal-to-noise at high
spatial frequencies) than a conventional long exposure image.
