Aperture area


Aperture is a “hole” or an opening through which light travels. The aperture of an optical system is the opening that determines the cone angle of a bundle of rays that come to a focus in the image plane.
The f-number (sometimes called focal ratio, f-ratio, f-stop, or relative aperture) of an optical system is the ratio of the lens’s focal length to the diameter of the entrance pupil.
The focal length of an optical system is a measure of how strongly the system converges or diverges light.
The amount of light captured by a lens is proportional to the area of the aperture.

Related formulas


AAperture area (cm2)
fFocal length of the lens (cm)
NFocal number (f-number) (dimensionless)