Exposure: F/stop (Fnumber or Aperture)

So far so good�but there�s one other aspect to consider, and that�s the fact that camera lenses can change the diameter of their aperture, thus letting in more or less light as needed. Every camera�no matter what it uses for film�controls the exposure with some sort of aperture.

f/stops = The size of a camera�s aperture at any given moment = f number of the lens
f/stops = the focal length of the lens / the diameter of the opening of the diaphragm.
So, if diameter is high f/stop is small and if diameter is small f/stop is high



Example,
f/22 is very, very small (not much light gets through to the image sensor or film)
f/1.2 is a huge opening that floods the image sensor or film with light.

And relationship of Same ISO can use many ways of shutter speed and aperture As you reduce the shutter speed, you need to increase the diameter of the aperture in order to have enough light to take a properly exposed picture. Of course, there�s a relationship between aperture, shutter speed, and your Image sensor/film�s ISO rating.

At a given ISO, you can take a picture with a specific aperture/shutter combination. If you double the film speed (ISO) without changing the lighting conditions, though, you have to adjust the aperture and shutter speed so that you still get a properly exposed picture.