essential skills: digital photography in available light
Depth of fi eld
In addition to choosing the focal point of the image the photographer can also control how much
of the image appears sharp or ‘in focus’. As the aperture of the lens is progressively reduced
in size, subjects in front and behind the point of focus steadily begin to appear sharper. By
choosing the aperture carefully the photographer may be able to single out one person in a
crowd or the entire crowd to be in focus. In this way communication can be dramatically altered.
The zone of acceptable sharp focus is described as the ‘depth of fi eld’.
Depth of fi eld can be described as the nearest to the furthest distances from
the lens where the subject appears acceptably sharp.Shallow depth of fi eld (above left) is created using the wider aperture settings of the lens. Subject
matter behind and in front of the point of focus appears progressivley out of focus. Due to the
smaller sensors used in the prosumer digicams it is often diffi cult to achieve shallow depth of fi eld
unless you are working at the closest focusing distance of the lens, i.e. capturing an image using
a prosumer camera using a small sensor will lead to greater depth of fi eld than a DSLR using a
lens set to the same aperture.
Maximum depth of fi eld (above right) is created using the smaller aperture settings of the lens.
Subject matter immediately in front of the lens and subject matter in the distance may appear
acceptably sharp in the same image.
The widest apertures (f2, f4) give the least depth of fi eld.
The smallest apertures (f16, f22) give the greatest depth of fi eld.
The smaller the sensor the greater the depth of fi eld at the same aperture.Depth of fi eld preview
The changes to depth of fi eld affected by aperture are not readily seen in most DSLR cameras.
The subject is often viewed through the widest aperture that is held permanently open until the
actual exposure is made. This is to give the photographer a bright image in the viewfi nder. If the
photographer wishes to check the depth of fi eld at any given aperture they must use a ‘depth of fi eld
preview’ or review the image using the camera’s LCD screen. An advantage of using a prosumer
digicam is that a live preview of the depth of fi eld is available before the image is captured.
Aperture wide open Aperture stopped down to f22