What is Depth of Field (DOF)
One of the most powerful creative tools at the photographers disposal is the depth of field. It’s a creative technique in photography that brings out the focus of a particular matter in the image.
Depth of field (DOF) is simple the amount of the scene that appears to be sharp in your photograph. It’s determined by three factors – the aperture used, the focal length of the lens and the distance from the subject. Areas outside of the DOF are blurry.
A blurred background isolates the main subject from the distracting unimportant details and increases the three-dimensional illusion of the picture. Blurred parts in the picture can also be decorative, playing a very important part in the composition of the picture. The picture would be more pleasing to the eyes, if the main subject “stands out” from it’s surrounding.
When you want everything in the photographs as sharp as possible, you would require a large DOF,often called deep focus. But in some cases, like in portraits & macro photography, you may want to use a more creative approach, with the main subject of the picture being sharp, while de-emphasizing the foreground and background, which would require a small DOF, often called as shallow focus.
Shallow (Small) Depth of Field
When the aperture is large (ex. f/1.8), the area within the depth of field appears sharp, whereas the areas right in front of and beyond the depth of field appear blurry. It let’s you draw the viewer’s attention into specific parts of the image.
Shallow depth of field is used to isolate the subject from its surroundings. It’s used mostly in portraits & macro photography. As a very general rule, use apertures between about f/2.8 and f/8 for portraits where you want the background to be out-of-focus.
Below image has a bird, the only focal point of the photo, with tress in the background. By choosing a shallow depth of field, the background becomes nothing more than a beautiful canvas to display the foreground subject on.
Deep (Large) Depth of Field
When the aperture is small (ex. f/16), the area from front-to-back would be in focus. Large depth of field is mostly used in landscape photography. Use an aperture between about f/11 and f/22 for landscapes where you want everything from the foreground to the far distance to appear sharp.