In photography, the Depth of Field refers to the portion of a photograph that is in focus–specifically the distance between the nearest and farthest objects or surfaces in the photograph that appear acceptably sharp and in focus to the viewer.
In practical application, Depth of Field is almost entirely controlled by adjusting the camera’s aperture setting (the aperture is the opening of the mechanical iris in the lens that allows light to pass through to the film or sensor). Opening the aperture up decreases the depth of field and closing the aperture down increases the depth of field. If you, for example, wanted to take a picture of a particularly striking rose on a bush with a busy city intersection in the background (and wanted to avoid drawing attention to the billboards and buses) you would open the aperture so that only the rose fell within the Depth of Field and the background would appear dappled and out of focus. Conversely if you wanted to capture everything to show the contrast between the organic rose and the inorganic cityscape, you could close the aperture down and expand the Depth of Field so that everything from the rose petals to the distant billboards is sharp and in focus for the viewer.
- By Jason Fitzpatrick on 04/13/13