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What is Diagonal FOV?

Published in Field of View 4 mins read

Diagonal field of view (FOV) is the measurement of the visible area captured by a camera lens, expressed in degrees. It represents the widest angle a camera can see, encompassing the entire image sensor from one corner to its opposite.

Understanding Field of View (FOV)

Field of View (FOV) defines the extent of the observable world seen through a camera, lens, or display. While often used interchangeably, FOV can be measured in three primary ways:

  • Horizontal FOV: The angle measured across the width of the image.
  • Vertical FOV: The angle measured across the height of the image.
  • Diagonal FOV: The angle measured from one corner of the image sensor to the opposite corner, providing the broadest perspective.

Why Diagonal FOV Matters

Diagonal FOV is particularly significant because it reflects the maximum achievable viewing area of a camera system. It gives a comprehensive understanding of how much of a scene the camera can capture.

  • Comprehensive Coverage: It indicates the total scene capture capability, useful for comparing different camera systems for their overall viewing capacity.
  • System Design: Crucial for designers of optical systems, security camera setups, and virtual reality applications to ensure complete scene inclusion and optimal placement.
  • Immersive Experiences: In virtual reality (VR) and augmented reality (AR), a larger diagonal FOV contributes to a more immersive user experience by filling more of the user's peripheral vision, making the digital world feel more expansive.

How Diagonal FOV is Measured

As per its definition, diagonal FOV is the angle between two imaginary lines extending from opposite corners of the camera's image sensor, passing through the center of the lens and extending outwards to the edges of the field of view. This geometric calculation accounts for the full extent of the rectangular image sensor, from its bottom-left to its top-right corner, for instance.

Factors Influencing Diagonal FOV

Two primary factors dictate a camera's diagonal FOV:

  1. Lens Focal Length: Shorter focal lengths (e.g., wide-angle lenses) result in a wider FOV, while longer focal lengths (e.g., telephoto lenses) yield a narrower FOV.
  2. Image Sensor Size: A larger image sensor, when paired with the same focal length lens, will capture a wider field of view than a smaller sensor.

Consider how focal length typically impacts FOV:

Focal Length (mm) Approximate Diagonal FOV (Degrees)* Typical Use Case
1.8 150-180 Fisheye, panoramic
2.8 100-120 Wide-angle security
4 80-90 General purpose security
12 25-30 Zoom, distant monitoring

Note: FOV values are approximate and also depend on the specific sensor size and lens design. Values provided are for common security camera sensor sizes (e.g., 1/2.8" or 1/3").

Practical Applications and Examples

Understanding diagonal FOV is essential in various fields:

  • Security and Surveillance: Ensures maximum area coverage with fewer cameras. A camera with a wide diagonal FOV can monitor a larger room or outdoor space efficiently, reducing blind spots.
  • Photography and Videography: Helps photographers select the right lens to capture a desired scene, from vast landscapes to intimate portraits. Wide diagonal FOV lenses are often chosen for architectural, interior, or group shots.
  • Virtual Reality (VR) and Augmented Reality (AR): A larger diagonal FOV in VR headsets provides a more natural and immersive experience, contributing to a greater sense of "presence" within the virtual environment.
  • Automotive Cameras: Used in backup cameras and advanced driver-assistance systems (ADAS) to provide a broad view of the vehicle's surroundings, crucial for parking assistance and collision avoidance.

Comparing FOV Types

While diagonal FOV provides the overall maximum angle, horizontal and vertical FOVs are also important for specific applications. For instance, horizontal FOV is often used to determine how many lanes of traffic a camera can cover, while vertical FOV might be critical for monitoring shelves in a retail environment. Diagonal FOV simply gives the overarching capacity, as it encompasses both horizontal and vertical dimensions. It's the "big picture" measurement of what the camera can see.