Perception of depth in photographs

In a world of computer-manipulated pictures easier than ever to achieve, many photographers and artists are called upon to combine images from various sources for illustrative purposes such as 'web pages', advertisements, public relations brochures, etc. To achieve an accurate interpretation in a finished composite illustration made up of photographs manipulated using a computer (or using conventional methods) the illustrator must be aware of the design and compositional elements of each image incorporated in the final illustration. Design and composition elements include: lighting direction and shadow, density, colour balance, etc. Yet another design and composition element too often overlooked is depth cues. Depth cues are the means by which the viewer perceives depth in a two-dimensional image, in this case: a photograph. This paper describes and illustrates the known depth cues contained in the photographic image.