A photomontage is, literally, a montage created with photographic images, using transparencies, prints, negatives, scans, or some combination these elements. They may be captured with a film camera, a digital camera, a scanner, or even a pinhole camera.
British photographer Henry Peach Robinson (1830-1901) combined multiple negatives to create single images in the late 1850s, and is credited as the innovator of the technique which spawned the genre. Photomontage went on to become one of the (many) elemental techniques of the surrealist movement. Unfortunately, Henry went on to suffer from over-exposure to toxic chemicals and was forced to give up photography at the age of thirty-four.
Today, the layers of a photomontage are likely to include Photoshop adjustment layers, blending modes, and hand-painted digital masks, all selectively interacting with the layers of images. Some montage images leave no doubt about their intent. Others manage to sneak by many viewers, leaving them to wonder, "What is it about this image?"