Shift-and-add

For the shift-and-add multiplication algorithm, see multiplication algorithm#Shift and add.

The shift-and-add method (more recently "image-stacking" 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-stabilisation feature on some cameras. The method involves calculation of the differential shifts of the images. The images are then shifted back to a common centre and added together. This provides an image with higher resolution (higher signal-to-noise at high spatial frequencies) than a conventional long exposure image. A number of software packages exist for performing this, including IRAF, RegiStax, Keiths Image Stacker, hugin (open source) and Iris.

See also

• Focus stacking
• Lucky imaging

References

• Baba, N.; Isobe, S.; Norimoto, Y.; Noguchi, M. Stellar speckle image reconstruction by the shift-and-add method, Applied Optics (ISSN 0003-6935), vol. 24, May 15, 1985, p. 1403-1405.
• Christou, J. C., Image quality, tip-tilt correction, and shift-and-add infrared imaging, Publications of the Astronomical Society of the Pacific, vol. 103, Sept.1991, p. 1040-1048.