Aperture value and depth of field
The depth of field is the area in the picture with an accaptable sharpness, providing the viewer with details of the subject and this is of course very important and can change the way the picture is viewed upon. Though, the depth of field can be altered by choosing different aperature values and we have chosen to illustrate this with a couple of pictures:
Canon EOS 40D
Canon EF 50mm f/1,8 II
Different aperture values will give you a different depth of field. The focal length of the lens as well as the distance to the subject will also have an effect on the depth of field but we will here mainly look at the aperture value.
Please look at these pictures.
The different combinations will all give you a faultless picture, but by changing the aperture you can get the desired depth of field in your picture. Using a very low aperture such as f/1,8 may be good if you in a portrait only wish to set the eyes in focus but the rest slightly out of focus. This becomes possible because the f/1,8 aperture gives a very short depth of field. If you are looking for the possibility to take pictures with a very short depths of field you should look for a bright lens, where the aperture value is low.