The computer and digital camera have allowed the photographer to elevate his photographs into the works of art only recently. For centuries before the invention of photography, the task of documenting reality in all its splendor was the sole province of the painter. Different schools of art such as Impressionism, Cubism, and Realism surfaced at different time periods, each exercising artistic license to produce different interpretations of reality
Some artistic movements emphasized colors, others lines and contours. Yet, despite their welter of differences, all artistic movements had something in common–their judicious use of the color white. White has a very high luminosity and the human eye is instinctively, irrepressibly drawn to it. Including it in a dark and somber painting with muted colors would undermine the work’s critical theme. Yet, in photographs throughout the twentieth century, white skies and “blown” highlights were a photographic mainstay, to the detriment of the medium’s message. The reason for this occurrence is that reality has too high a contrast ratio to be adequately captured by film or digital media in a single exposure.
Prior to the advent of digital photography, film photographers grappled with the issue of producing photographs that covered the range of luminosities from shadows to highlights without loss of detail. Gustave Le Gray, a nineteenth century French photographer pioneered the use of high dynamic range photography. He is most famous for his seascape photography, in which in order to represent the extreme range of luminosities between the sea and sky; he blended two exposures, using one negative for the sea and another for the sky.
The photographic luminaries Ansel Adams and W. Eugene Smith went to great lengths to increase the dynamic range of their final prints. Adams invented his highly regarded Zone System, which meticulously ascribed luminosities to different parts of his scene, to determine not only an appropriate exposure, but also those areas in a scene requiring selective dodging and burning in the darkroom. Other film photographers blended as many as three different exposures, each taken with a different color filter (red, green, or blue) in order to increase dynamic range.
A high dynamic range image is produced by combining in special software multiple exposures of the same scene. When the high dynamic range image is produced, it encodes such a high range of luminosities that most modern computers displays cannot render this information in its raw state. The process of converting this raw date to a viewable form is called tone-mapping. The final tone-mapped image is what is often (incorrectly) referred to in common parlance as an HDR image. HDR tone-mapping often produces results so dramatic as to render the original images pale in comparison to the final tone-mapped image.
