CCTV Lens & FOV
Enter the distance to the target, the sensor, the focal length and the horizontal resolution and get the HFOV, the scene width, the px/m and the DORI level (EN 62676-4) reached, with the maximum distance for detection, observation, recognition and identification.
Maximum distance per DORI level
| Level | Threshold | Max. distance | Status at D |
|---|
Status at D shows whether the threshold of each level is
met at the entered distance.
How it is calculated · FOV, px/m and DORI (EN 62676-4)
1. Horizontal field of view:
HFOV = 2·atan(sensorW / (2·f)) · 180/π, with the sensor
width and focal length in mm.
2. Scene width at distance
D: width = D · sensorW / f (in metres, with
D in metres).
3. Density:
px/m = horizRes / scene_width. More pixels on the
target means more detail.
4. DORI thresholds (EN 62676-4, px/m):
Detection 25, Observation 63,
Recognition 125, Identification 250.
5. Maximum distance for a level:
Dmax = horizRes · f / (threshold · sensorW). Up to that
distance the required density is kept.
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How it works
The calculator solves the optics of an IP camera from four inputs: distance to the target, sensor width (from 1/4 inch to 1/1.8), lens focal length and horizontal resolution. The horizontal field of view comes from HFOV = 2·atan(sensorW / (2·f)), the scene width at distance D is D · sensorW / f, and the detail density is px/m = horizontal resolution / scene width.
That density is compared against the DORI thresholds of EN 62676-4: Detection 25 px/m, Observation 63, Recognition 125 and Identification 250. The tool reports the level achieved at the entered distance and the maximum distance for each level using Dmax = resolution × focal / (threshold × sensorW), which helps choose lens and resolution before installing.
Example: a 1080p camera with a 4 mm lens — can it identify at 10 m?
- 1/2.8 inch sensor (5.0 mm wide) and 4 mm focal:
HFOV = 2·atan(5/8) ≈ 64°. - Scene at 10 m:
10 × 5 / 4 = 12.5 mwide → density1920 / 12.5 ≈ 154 px/m. - At 154 px/m you reach Recognition (≥125), but not Identification (≥250).
- Identification only up to
1920 × 4 / (250 × 5) ≈ 6.1 m: identifying at 10 m requires a longer lens or more resolution.