How to choose CCTV camera lens: 2.8mm vs 3.6mm vs 4mm vs 6mm focal length and field of view guide

A 2.8mm lens gives you a wide field of view (often around 100-110 degrees on common 1/2.8-inch cameras) and works well for covering large areas like parking lots, warehouses, and shop floors. If you need to identify faces or number plates at a distance, move to a 4mm or 6mm lens instead - they narrow the view but put more pixels on the subject, making identification easier.

How focal length works in cameras?

Focal length is the distance (in mm) between the lens's optical centre and the image plane. A shorter focal length produces a wider field of view, so the camera captures more of the scene. A longer focal length narrows the view but makes distant objects appear larger in the frame.

This is a tradeoff, not a quality difference. A 2.8mm lens doesn't produce worse images than a 6mm - it just spreads its pixels across a wider area, so each object gets fewer pixels. A 6mm lens concentrates those pixels on a smaller slice of the scene, giving you more detail per object at the cost of coverage.

Which focal length for which situation?

2.8mm (typically 95-110° FoV) - best for open areas where you want maximum coverage with fewer cameras. Rooms, retail floors, warehouses, parking lots. You'll see more, but distant faces and number plates will occupy fewer pixels.

3.6mm (typically 80-90° FoV) - a common general-purpose lens. Slightly narrower than 2.8mm with better subject detail at mid-range. Good for shop entrances, residential gates, medium corridors.

4mm (typically 75-85° FoV) - similar to 3.6mm with a touch more reach. A strong option for entrances, reception areas, and hallways where you want more detail on people at moderate distances.

6mm (typically 50-60° FoV) - narrow and focused. Use this for long corridors, driveways, gates, or areas where you need more detail on a specific distant subject. You'll need more cameras to cover the same area a 2.8mm lens handles in one shot.

Varifocal (2.7-13.5mm) - adjustable during installation. Useful when you're not sure of the exact angle you'll need, or when the mounting position is fixed and you want to dial in the right balance on-site. Costs more than fixed-lens cameras.

Does the sensor size matter?

These FoV numbers are rough estimates for common 1/2.8-inch sensors and can vary between camera models. A 1/3-inch sensor with the same lens generally gives a slightly narrower view. Always check the camera's spec sheet for the actual horizontal FoV rather than relying on the focal length alone.