Managing Depth of Field in Photographic Compositions
When composing photographic images, depth of field is one of the main considerations to remember. Depth of field refers to how much of your scene is in sharp focus. The shallower your depth of field, the more your focal point stands out against the blurred elements. The greater your depth of field, the more detail you reveal throughout the scene. It can be used to tell viewers where exactly to look in a frame.
The following two compositional tools control how much depth of field occurs in a photograph:
Aperture: Your aperture determines how much light can enter your lens in a given moment. The larger the aperture opening, the shallower your depth of field. So, if you close your aperture, you can increase your depth of field.
Magnification: Your lens choice determines how much a scene is magnified in a photograph, and magnification determines depth of field. A wide-angle lens doesn't magnify a scene at all, so it provides a greater depth of field than a telephoto lens (also referred to as a long lens), which magnifies the scene to allow you to get tighter crops from far away. The longer a lens is, the shallower the depth of field it produces.
To maximize depth of field, use a wide-angle lens and shoot with a small aperture opening. To minimize depth of field, use a telephoto lens and shoot with a large aperture opening.