An f-number is a measure of the light-gathering ability of an optical system such as a camera lens.

The f/# (pronounced “F-number”) setting on a lens controls overall light throughput, depth of field (DOF), and the ability to produce contrast at a given resolution. Fundamentally, f/# is the ratio of the focal length, (f) (f), of the lens to the effective aperture diameter (∅EA) (∅ EA):

Numerical aperture (NA) refers to the cone of light that is made from a focusing lens and describes the light gathering capability of the lens (similar to f/# ). NA is defined by the following equation, where n is the index of refraction of the medium (often n=1 for air), and α is the half angle of the cone of light exiting the lens pupil.

What is an f-number (ƒ/#)? An f‑number (ƒ/#) or f‑stop refers to the ratio of a lens’s focal length to its aperture diameter and indicates the amount of light coming through the lens. F-numbers can change throughout a lens’s zoom range, lenses are …

2025年3月31日 · The f-number, also known as the focal ratio or f-ratio, relates the focal length of a lens to the diameter of its aperture. It is expressed as a ratio: f/N, where f is the focal length and N is the aperture diameter.

The f-number of an object is the ratio of focal length and aperture diameter, and used for indirectly indicating the aperture size. Large numbers imply small apertures, leading to reduced light throughput and an increased depth of field.

2024年12月26日 · What Is The F Number? The f number, or f-stop, is a quantitative measure of the aperture opening in a camera lens, indicating the amount of light that passes through the lens to reach the camera sensor. Essentially, the f number describes the diameter of the aperture opening relative to the focal length of the lens.

In optics, the f-number (sometimes called focal ratio, f-ratio, or relative aperture [1]) of an optical system expresses the diameter of the entrance pupil in terms of the effective focal length of the lens; in simpler terms, the f-number is the focal length divided by the aperture diameter.

F-number DEFINITION: The inverse number of a relative aperture. The value obtained by dividing the focal length by the effective aperture. DESCRIPTION: F-number (F) is expressed by the following formula. Generally, f-numbers are used to indicate the amount of light that passes through the lens.

2023年6月12日 · The f-number (also known as the f-stop) is a dimensionless value that represents the ratio of a lens’s focal length to the diameter of the aperture opening. It determines the size of the...