Depth of Field refers to a particular effect in photography that deals with the “acceptable sharpness” of a subject within a particular scene. In a standard shot the depth of field is large, making everything in the picture acceptably sharp. When a shallow depth of field is utilized, the subject may stand out more compared to a normal shot.
For example; The image on the right displays a large depth of field. The entire keyboard is sharp. There is no particular emphasis placed on any one location. In the shot on the left of the same keyboard, a shallow depth of field is used to create emphasis on a single spot in the frame.
Creating an effective depth of field effect is fairly simple on most cameras. The aperture plays an important role in creating the effect, depending on its diameter you can achieve harsher or softer effects. The larger the diameter of the aperture, the larger the depth of field, resulting in a normal shot where everything becomes acceptably sharp. Moving the aperture size in the opposite direction will allow the photographer to focus on a single part of the frame. The smaller the aperture becomes, the larger the effect becomes…
There are drawbacks in certain situations for taking depth of field shots. The first is that with every decrease in aperture size, you allow less light to reach the film/sensor. This means you must decrease the shutter speed to compensate and to get the correct exposure.
Unless you have a tripod handy, you may succumb to camera shake. Additionally, depending on the camera, you may end up with an underexposed shot as you may not be able to compensate enough to get the desired effect. Without enough compensation for light to pass to the sensor, you will end up with a shot that is far too dark.
Focus stacking is the process of taking multiple shots of the same subject using different aperture and shutter speed settings. These photos are then layered atop one another. This can help counteract situations where you can’t get the effect you had in mind quite right.