Aperture is measured in f-stops.
Understanding Aperture Measurement
In photography, aperture refers to the opening in the lens through which light passes to reach the camera sensor or film. The size of this opening is crucial as it affects both the amount of light entering the camera (exposure) and the depth of field (the area in focus).
Based on the provided information, aperture is measured in f-stops. An f-stop, also known as an f-number, serves as the standard unit for quantifying aperture size.
What is an F-Stop?
An f-stop is not a direct measurement of the physical size of the aperture opening in millimeters or inches. Instead, it is a relative measure. According to the reference:
- An f-stop is the ratio of the lens focal length divided by the diameter of the entrance pupil of the aperture.
- As a result, an f-stop represents the relative aperture of a lens.
- It is essentially a method to normalize the aperture setting across different lenses, regardless of their specific focal lengths or physical sizes.
This ratio means that the same f-stop number represents the same relative light-gathering ability, even if the physical aperture opening is different on a wide-angle lens compared to a telephoto lens. For example, an f/4 aperture on a 50mm lens has a physical opening diameter of 12.5mm (50mm / 4 = 12.5mm), while an f/4 aperture on a 200mm lens has a physical opening diameter of 50mm (200mm / 4 = 50mm). Despite the physical difference, both are designated f/4 and allow a comparable amount of light through relative to their respective focal lengths.
The F-Stop Scale
F-stops follow a standard sequence, where each stop lets in half the amount of light as the previous stop (or double the amount of light if moving in the other direction). Common full f-stops include:
- f/1.4
- f/2
- f/2.8
- f/4
- f/5.6
- f/8
- f/11
- f/16
- f/22
- f/32
Note: Smaller f-numbers (like f/1.4) indicate a larger physical aperture opening, letting in more light, while larger f-numbers (like f/22) indicate a smaller physical opening, letting in less light.
Understanding f-stops is fundamental for controlling exposure and depth of field in photography.
