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What Are the Aperture Stops?

Published in Photography Basics 3 mins read

Aperture stops, commonly known as f-stops (or f-numbers), are standardized measurements that denote the size of the lens's aperture opening, controlling the amount of light that reaches the camera sensor or film. They are fundamental to photography, directly impacting exposure and the visual effect known as depth of field.

Understanding F-Stops

Aperture is measured in f-stops. As defined, an f-stop (or f-number) is the ratio of the lens focal length divided by the diameter of the entrance pupil of the aperture. This means an f-stop represents the relative aperture of a lens, normalizing the aperture setting across different lenses regardless of their physical size.

A smaller f-number (e.g., f/1.4, f/2.8) signifies a larger aperture opening, allowing more light to pass through the lens. Conversely, a larger f-number (e.g., f/16, f/22) indicates a smaller aperture opening, restricting the amount of light.

Standard Aperture Stop Values

The f-stop scale is a geometric progression, where each "full stop" either halves or doubles the amount of light entering the lens compared to the previous or next stop. This is because each full stop represents a change in the aperture area by a factor of two.

Here are the common full-stop aperture values:

F-Stop Value Relative Aperture Size Light Transmission Depth of Field
f/1.0 Very Large Maximum Very Shallow
f/1.4 Large High Shallow
f/2.0 Large High Shallow
f/2.8 Moderately Large Good Moderate
f/4.0 Medium Standard Moderate
f/5.6 Moderately Small Less Deep
f/8.0 Small Less Deep
f/11 Small Minimal Very Deep
f/16 Very Small Very Minimal Extremely Deep
f/22 Extremely Small Least Maximum
f/32 Smallest Minimal Maximum

Note: Lenses may offer intermediate stops (e.g., f/3.5, f/6.3) or third-stop increments (e.g., f/1.8, f/2.2).

Practical Impact of Aperture Stops

Adjusting the aperture stop directly influences two crucial aspects of your photographs:

1. Exposure

  • Larger Aperture (Smaller f-number): Allows more light in, leading to brighter images. Ideal for low-light conditions or achieving faster shutter speeds to freeze motion.
  • Smaller Aperture (Larger f-number): Restricts light, resulting in darker images. Useful in bright conditions to avoid overexposure or to use slower shutter speeds for creative effects (e.g., motion blur).

2. Depth of Field

Depth of field refers to the range of distance within a scene that appears acceptably sharp.

  • Shallow Depth of Field (Smaller f-number):
    • Achieved with wider apertures (e.g., f/1.4, f/2.8).
    • Only a narrow plane of focus is sharp, while the foreground and background are blurred.
    • Commonly used in portrait photography to isolate the subject from the background, creating a pleasing bokeh effect.
  • Deep Depth of Field (Larger f-number):
    • Achieved with narrower apertures (e.g., f/11, f/16).
    • A greater portion of the scene, from foreground to background, appears sharp.
    • Ideal for landscape photography or group shots where you want everything in focus.

Examples of Aperture Stop Usage:

  • Portraits: Use f/1.8 – f/4.0 to create a shallow depth of field and make your subject stand out.
  • Landscapes: Use f/8.0 – f/16 to ensure sharpness from the immediate foreground to the distant horizon.
  • Low Light: Use f/1.4 – f/2.8 to gather more light and maintain a lower ISO or faster shutter speed.
  • Product Photography: Often uses f/8.0 – f/11 to ensure the entire product is in sharp focus.

Understanding and mastering aperture stops is essential for photographers to achieve precise creative control over their images.