Field of View Calculator — free FoV tool for camera lenses

Understanding Field of View Calculations

• Field of view depends on focal length and active sensor size
• HFOV/VFOV/DFOV use the formula: 2×arctan(dimension/(2×f)) for rectilinear lenses
• Wide-angle lenses require distortion correction for accurate FOV
• Scene width at distance: Width ≈ 2×WD×tan(HFOV/2)
• This calculator uses a non-standard but practical distortion model for real lenses

The basic field of view calculation assumes an ideal pinhole camera model. For standard lenses with minimal distortion, the formula FOV = 2×arctan(sensor_size/(2×focal_length)) provides accurate results. However, real wide-angle and fisheye lenses deviate significantly from this model at the image edges.

Example FOV Calculations

• 1/2.3" sensor (6.3×4.7mm), 2.8mm lens: HFOV ≈ 103.8°, scene width ≈ 2.10m at 1m distance
• 1/2.3" sensor (6.3×4.7mm), 6mm lens: HFOV ≈ 57.6°, scene width ≈ 1.08m at 1m distance
• 2/3" sensor (8.8×6.6mm), 12mm lens: HFOV ≈ 40.5°, scene width ≈ 0.73m at 1m distance

Note: These calculations assume minimal distortion. Real lenses may differ by 10-25% at wide angles.

Four Key Parameters for FOV

1) Focal Length

The effective focal length (EFL) determines the angular field of view. Shorter focal lengths provide wider coverage, while longer focal lengths narrow the field of view but increase magnification. Use the actual EFL, not the back focal length (BFL) which only describes the physical distance from the last lens element to the sensor.

2) Sensor Dimensions

Use the active sensor area from your camera datasheet, not the nominal format size. A "1/2.3 inch" sensor actually measures about 6.3×4.7mm active area. The field of view calculator needs these precise dimensions for accurate results.

3) Lens Coverage

The lens image circle must exceed your sensor diagonal to avoid dark corners (vignetting). Most M12 mount holders support up to 12mm diameter image circles. Verify coverage when using large sensors or extreme wide-angle lenses.

4) Distortion and Projection

Barrel distortion increases the effective field of view by compressing more scene content at the image edges. Fisheye lenses use specific mathematical projections (equidistant, stereographic, orthographic) that dramatically alter the FOV compared to standard rectilinear lenses. This calculator supports multiple projection models to match your lens type.

Selecting the Right Focal Length

To determine the required focal length for your application, rearrange the formula: focal_length = sensor_width / (2 × tan(HFOV/2)). For example, to achieve 60° horizontal FOV on a 6.3mm wide sensor, you need approximately 5.5mm focal length.

Remember that depth of field changes with focal length. Shorter focal lengths provide greater depth of field at the same f-number, making them ideal when you need both wide coverage and extended focus range. Browse our M12 lenses or C-mount lenses sorted by focal length.

Common FOV Calculation Mistakes

Confusing Total FOV with Angular Resolution

The field of view tells you the total angular coverage, while angular resolution (IFOV) tells you the angle per pixel. IFOV = FOV / pixel_count. For a 90° FOV across 1920 pixels, each pixel covers 0.047° or about 2.8 arcminutes. This determines the smallest resolvable detail at a given distance.

In low-distortion rectilinear lenses, angular resolution varies across the image. Edge pixels cover more angular area than center pixels due to the projection geometry. A pixel at 30° off-axis represents approximately 33% more angular area than a central pixel, affecting detection algorithms and measurement accuracy.

Using Wrong Working Distance Reference

Working distance can be measured from the lens front, the mount flange, or the entrance pupil. For FOV calculations, use the distance from the entrance pupil (approximately at the lens center for simple lenses). For mechanical clearance, use the distance from the front lens element. This difference can be 20-50mm in longer focal length lenses.

Using FOV Results

OpenCV Camera Calibration

For computer vision applications, the OpenCV camera calibration functions can determine your actual lens parameters from calibration images. The standard model uses five distortion coefficients (k₁, k₂, p₁, p₂, k₃) for radial and tangential distortion.

The OpenCV fisheye module implements the Kannala-Brandt model with four coefficients, optimized for lenses with FOV exceeding 150°. Note that undistorting a fisheye image to rectilinear projection significantly reduces the usable field of view—a 180° fisheye typically yields only 100° of usable rectilinear coverage.