CCTV Lens Sizes Explained: 2.8mm vs 4mm vs 6mm vs Varifocal

What the millimetre number means

The mm figure on a CCTV camera is the lens focal length. A small number (2.8mm) gives a wide view; a bigger number (8mm, 12mm) gives a narrow, zoomed-in view. The same camera with a wider lens sees more of the area but less detail at any given distance — the pixels are spread across a bigger scene.

Choosing the lens is therefore choosing between coverage and detail. It matters as much as resolution, and it is the most common thing we change when re-planning an existing system.

Typical field of view and use

The exact angle depends on the camera’s sensor size, so check each datasheet. These are typical figures for common 2MP–4MP cameras:

Matching lens to distance

As a rough guide for a 4MP camera, a 2.8mm lens can identify faces only within a few metres; a 6mm lens extends that to somewhere around 6–8 metres; and 8–12mm lenses push it further. Beyond identification range the camera can still observe activity and detect intruders, which is fine for compound and perimeter cameras.

If you need both a wide view and faces at the gate, use two cameras — one wide and one tight on the entry point — rather than one compromise lens.

Fixed vs varifocal vs motorised

• Fixed lens: lowest cost and simplest. Good when the distance is known and standard — most indoor cameras.
• Manual varifocal: the installer adjusts zoom and focus on site. Useful for gates and aisles where the exact distance matters.
• Motorised varifocal: zoom and focus are adjusted remotely from the recorder or software. Easy to fine-tune later and ideal for high mounting points.
• PTZ: the camera moves and zooms in real time, for operators watching large areas.

Common lens mistakes

• A 2.8mm camera at the gate 10 metres away: you see the gate, but not who walked through it.
• A narrow lens in a small room: it sees one wall and misses the door.
• Wide lenses mounted very high: distortion at the edges and tiny people in the middle of the frame.
• Ignoring the night view: IR range should match the distance the lens is set for.

How we choose on a survey

We stand where the camera will go, measure the distance to the point that matters, decide whether it must identify, recognise or just detect, and pick the lens that gets there. For warehouses, gates and campuses with varied distances, varifocal cameras save a lot of guesswork.

Example: lenses for a factory gate

At a factory gate, three cameras do three different jobs. A 2.8 mm camera on the security cabin gives a wide overview of the gate, guard and both lanes. A 6 mm camera aimed at the point where vehicles stop for the barrier fills the frame with the driver and vehicle front, close enough to read faces and clearly see the vehicle. A varifocal camera on the pedestrian gate, zoomed to about 4 mm during installation, frames people walking through at face height. Using one wide lens for all three would have given a nice overview and no usable evidence.

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