Numbers on the lens aperture ring and the camera's LCD (where applicable) that indicate the size of lens aperture. The lower the number the larger the aperture. As the scale rises, each number is multiplied by a factor of 1.4. Standard numbers are 1.0,1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, etc., each change resulting in a doubling or halving of the amount of light transmitted by the lens to the film.