Lesson two: Depth of field & ApertureLens aperture controls something referred to in photography as ‘depth of field’. Depth of field is a phenomenon caused by the limitations of the human eye. When a lens is focused, light is formed into a sharp point. However, light reflecting from other parts of the scene, closer to or further from the point of focus (ie, areas that are out of focus) instead forms blurry circles. The further from the point of focus, the blurrier these circles – and the relative part of the scene – become.
Camera School: Master Aperture Technique