4mm Standard
61.9° horizontal field of view - Complete coverage reference guide
About the 4mm lens
A 4mm lens provides about 70° horizontal field of view — close to what a person sees when scanning a scene without turning their head. This makes it the most "natural" CCTV focal length and the default choice for general-purpose installations where you want a balance of coverage area and identification distance.
Best for
- •General building monitoring across rooms, corridors, and small open spaces
- •Residential driveways, gardens, and back yards where typical recognition distances are 5–12 m
- •Shop entrances, cash registers, and POS-area surveillance
- •Standard parking spaces (covering 2–3 spots from a single mount)
Trade-offs
- •Coverage is moderate — for a 10m wide area, the camera must be mounted roughly 7m back
- •Faces remain identifiable up to about 10 meters in good light, dropping fast beyond that
- •Less suited to corner-to-corner room coverage than 2.8mm or 3.6mm options
Real-world example
A 4mm lens at 3 m mounting height covers a 4 m wide area immediately below and identification of faces remains good up to roughly 10 m away. Most NVR vendors quote "coverage" specs assuming 4mm focal length — when you see "covers up to 12m identification" in marketing materials, that figure typically assumes a 4mm lens on a 1/3" sensor.
Compared to other focal lengths
4mm is the benchmark against which other lenses are measured. Going wider (3.6/2.8mm) trades distance for area; going longer (6/8/12mm) trades area for distance. Most multi-camera installations use a mix of 4mm for general coverage and 6–8mm for chokepoints.
Coverage Width at Different Distances
| Distance | Coverage Width | Use Case |
|---|---|---|
| 5m | 6.0m | Entrance/POS area |
| 10m | 12.0m | Retail floor, office |
| 15m | 18.0m | Warehouse aisle, parking |
| 20m | 24.0m | Warehouse aisle, parking |
| 30m | 36.0m | Parking lot, perimeter |
| 50m | 60.0m | Parking lot, perimeter |
| 75m | 90.0m | Long-distance monitoring |
| 100m | 120.0m | Long-distance monitoring |
Other Lens Options
Calculate for Your Setup
Use our FOV calculator to experiment with different focal lengths and distances.