Understanding aperture values The shutter speed determines the length of time the light has to expose the film. The aperture is a measure of the size of the opening that light passes through. For an equal exposure, the longer the exposure time allowed by the shutter speed, the smaller the aperture opening. If the shutter speed must be made faster, then the aperture has to be opened wider in order for the same amount of light to expose the film. Aperture values are expressed in numbers called f-stops. A small aperture has a large number; f/22, for example, which seems a little more than a pinhole. A large aperture, f/1.4, has a small number. The numbers engraved on the aperture ring of the lenses are the f-stops, and each is an opening double or half the size of the next aperture value. << Back to Main . 1 . 2 . 3 . 4 . 5 . 6 . 7 . 8 . 9 . 10 . 11 .