A photographic mosaic is a composite image assembled from a collection of individual photographs arranged and joined together in a patchwork pattern, with adjacent images overlapping slightly at their edges to create a seamless or near seamless continuous picture covering a wider area or subject than any single photograph could capture alone. The technique allows vast subjects, landscapes, panoramic views, aerial surveys, or architectural subjects of great scale to be recorded comprehensively and in considerable detail by combining multiple individual images into a single unified whole.
The creation of a photographic mosaic requires careful and systematic photography of the subject, typically following a structured shooting pattern that ensures complete coverage of the entire area with sufficient overlap between adjacent frames to allow them to be accurately aligned and joined during assembly. The degree of overlap between adjacent images is an important practical consideration - too little overlap can leave gaps or make accurate alignment difficult, while excessive overlap increases the number of images required and the complexity of the assembly process. An overlap of between twenty and thirty percent between adjacent frames is generally considered sufficient for most mosaic applications.
In traditional photographic practice, mosaics were assembled manually by physically cutting and mounting prints in alignment on a backing board, carefully matching tones, colours, and features across the join lines between adjacent images. Aerial photography made particularly extensive use of mosaic techniques, with overlapping aerial photographs assembled into large scale photographic maps of terrain, urban areas, agricultural land, and other subjects of geographical or military interest, providing a level of detail and coverage that conventional cartographic methods alone could not achieve.
In digital photography, the assembly of photographic mosaics has been transformed by dedicated panoramic stitching and image assembly software, which can automatically analyse a set of overlapping images, identify and match corresponding features across adjacent frames, warp and align the images to compensate for lens distortion and perspective differences between frames, and blend the overlapping regions seamlessly to produce a finished composite that shows no visible joins. Software such as Adobe Photoshop's Photomerge function, PTGui, and Hugin has made the creation of high quality photographic mosaics and panoramas a straightforward and accessible process for photographers at all levels, enabling the production of extremely high resolution composite images that combine the detail of individual high resolution frames with the sweeping coverage of a wide panoramic or aerial view.
The term mosaic is also used in a different but related context within digital imaging to describe the Bayer mosaic - the colour filter array pattern of red, green, and blue filtered photosites arranged in a mosaic pattern across the surface of a digital image sensor, which forms the basis of colour capture in the majority of digital cameras.