20Concepts in PhotographyDepth of fieldPortraits or still-life photos mostly acclaimed by people are the ones onwhich the background is out of focus so the subject looks pronounced.Depending on the focused areas, a photo can be blurred or sharpened.This is called ‘a low DOF’ or ‘a high DOF’.The depth of field is the focused area around the subject. Therefore,a small DOF signifies that the focused area is narrow and a large DOFmeans the focused area is wide.A photo with a small DOF, which stresses the subject and makes therest of it blurred, can be obtained by using a telescope lens or selectinga low aperture value. Conversely, a photo with a large DOF whichshows all the elements on the photo sharply focused can be achievedby using a wide angle lens or selecting a high aperture value.Small Depth of Field Large Depth of FieldWhat controls out-of-focus effects?DOF depends on aperture valueThe wider the aperture is (namely the lower the aperture value), thelower the DOF becomes. Under the condition where the other valuesincluding shutter speed and ISO sensitivity are equal, a low aperturevalue leads to a photo with a low DOF.20 mm F5.7 50 mm F22
