Aperture is one of the two exposure parameters and one part of the exposure value composite that you will have to master as you start your journey into the exciting world of photography. Aperture is referred to as the hole in a lens that lets in light. It is a dimensionless number, a ratio between the actual diameter of the lens and the focal length. Aperture is referred to in f-stops or f-numbers.
If you see a chart that goes like this – f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8 then this is referred to as a whole stop (or full stop) aperture chart. Here, every fraction going right down the slide results in a halving of the amount of light captured by the previous aperture number and vice-versa.
A chart that reads like this – f/1, f/1.1, f/1.2, f/1.4, f/1.6, f/1.8 and so on is a one-third stop aperture chart. Here every fraction going towards right reduces the amount of light entering the camera by a factor of 1/3 and vice-versa.
Aperture also controls the depth of field of your images.