What to We Mean by a Stop When Talking About Photography

When talking about photography a ‘Stop’ is a unit of measurement used to describe each step of opening or closing a lens’ aperture. On lens’ with an aperture ring a stop can be thought of as one physical click of the aperture ring. One stop is equal to one EV and they relate to the following values: 1.8, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 64. A lower number refers to a wider aperture, great for shooting in low light conditions but prone to a loss of overall image sharpness. For this reason a photographer will often “stop down’ their lens to increase sharpness within an image.