What is Aperture?
The terms f-stop and aperture are often used interchangeably, this is incorrect.
The hooked “f” is shorthand for f-stop, like the ”s.” after a shutter speed is short for seconds.
f/2.8 and f/8 are two examples of common f-stop settings, where 2.8 & 8 are the f-stop values, respectively.
F-Stop = Lens Focal Length (mm) / Aperture Diameter (mm)
The aperture diameter is the straight line distance from one side of the aperture to the other side of the aperture, crossing directly through the aperture’s center.
The lens focal length determines the composition, magnification, & field of view, as described in the section below.
The graphic shows increasing f-stop values with decreasing aperture diameters.
- Aperture refers to aperture diameter, where light enters the front of the lens.
- F-stop is the ratio of lens focal length to aperture diameter.
- F-stop can be referred to as f-number or f-stop value. They are the same.
The hooked “f” is shorthand for f-stop, like the ”s.” after a shutter speed is short for seconds.
f/2.8 and f/8 are two examples of common f-stop settings, where 2.8 & 8 are the f-stop values, respectively.
F-Stop = Lens Focal Length (mm) / Aperture Diameter (mm)
The aperture diameter is the straight line distance from one side of the aperture to the other side of the aperture, crossing directly through the aperture’s center.
The lens focal length determines the composition, magnification, & field of view, as described in the section below.
The graphic shows increasing f-stop values with decreasing aperture diameters.
For example, using the equation above, if the lens focal length is 50mm and the aperture diameter is 25mm, then f-stop = 50mm/25mm = 2, denoted as f/2.
For a lens focal length of 400mm and an aperture diameter of 50mm the corresponding f-stop = 8, denoted as f/8.
Photographers determine the f-stop and focal length with camera settings, controlling the corresponding aperture diameter where light enters the lens.
- The larger the f-stop value, the less light enters the lens, over a set exposure time.
- The smaller the f-stop value, the more light enters the lens, over a set exposure time.