Find the ideal lens focal length for your surveillance cameras. Input your sensor size, target distance, and required coverage width to calculate the perfect focal length for any monitoring scenario.
The right focal length depends on your monitoring distance, required coverage width, and identification needs. Use this table as a quick reference.
| Focal Length | Field of View (H) | Typical Distance | Best For | Typical Scenario |
|---|---|---|---|---|
| 2.8mm | ~100° | 1–5m | Wide area overview | Indoor rooms, corridors, small shops |
| 4mm | ~80° | 3–8m | Entrance monitoring | Doorways, reception areas, parking entrances |
| 6mm | ~55° | 5–15m | General surveillance | Parking lots, warehouses, medium areas |
| 8mm | ~40° | 10–25m | Person identification | Perimeter, large halls, outdoor areas |
| 12mm | ~28° | 15–40m | Long-range monitoring | Road monitoring, long corridors, perimeter |
| 25mm | ~14° | 30–80m | Detail capture | License plates, face recognition at distance |
| 50mm+ | <7° | 50–200m | Long-distance detail | Highway, border, critical infrastructure |
Varifocal lenses (e.g., 2.8-12mm) offer flexibility during installation but may have slightly lower image quality than fixed lenses. Use fixed lenses when the installation position and angle are precisely determined.
Larger sensors produce wider fields of view with the same focal length. A 4mm lens on a 1/2" sensor covers more area than on a 1/3" sensor. Always specify sensor size when ordering lenses.
For reliable face recognition, the face should occupy at least 1/10 of the frame width. At 10m distance with a 1/2.7" sensor, a 25mm lens is typically required for face-level detail.
License plate recognition requires the plate to occupy at least 1/8 of the frame width. Use a longer focal length (12-50mm) and position the camera at a 15-30° angle to the vehicle path.
For PTZ cameras or large-area monitoring where zoom capability is needed, motorized varifocal lenses allow remote adjustment without physical access to the camera.
Cameras with IR cut filters (ICR) automatically switch between day and night modes. Ensure the lens is designed for IR wavelengths to avoid focus shift between day and night operation.
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