The term refers to applications designed to merge multiple images of the same scene, each captured with slight variations in focus, exposure, or perspective. This process results in a final image exhibiting greater depth of field, reduced noise, or an expanded dynamic range than any single source image could provide. A common example is landscape photography where elements from foreground to background are brought into sharp focus by combining multiple images focused at different distances.
Combining multiple images into one superior quality image is crucial for specific photographic techniques. Benefits range from enhancing image sharpness and clarity in macro photography, to overcoming limitations of sensor dynamic range in high-contrast scenes. Historically, the process was painstakingly done manually using specialized darkroom techniques, but now, computer software significantly streamlines the process, increasing accessibility and efficiency.