Jan 08
Aperture explained: what do f-top numbers mean?
In optics, the f-number (sometimes called focal ratio, f-ratio, or relative aperture) of an optical system expresses the diameter of the entrance pupil in terms of the focal length of the lens; in simpler terms, the f-number is the focal length divided by the “effective” aperture diameter. It is a dimensionless number that is a quantitative measure of lens speed.
The smaller your f number (aperture AV number) the more light your camera sensor will see and if you have more light you can have faster shutter speeds. The cost = only small amount of your subject will be in focus.
The reverse is for larger f number. Less light gets in, slower shutter speed – more of your photo will be sharp.
