On this page
01. How focal length changes the picture02. Fixed vs varifocal03. Wide isn't always better04. FAQ
The lens focal length (in mm) decides how wide the camera sees. A 2.8mm lens gives a wide view with less detail at distance; 6mm or 12mm gives a narrow view with more detail further away. Fixed lenses are set at the factory; varifocal lenses can be adjusted on site to fit the exact scene.
Key takeaways
- Small mm = wide view, big mm = zoomed-in view.
- Wide lenses are great for rooms and doorways but poor for detail at distance.
- Varifocal (e.g. 2.8–12mm) lets the installer frame the scene precisely.
- Motorised varifocal lenses can be adjusted remotely, with no ladder needed.
01How focal length changes the picture
| Lens | View | Typical use |
|---|---|---|
| 2.8mm | Very wide | Rooms, reception, small yards |
| 4mm | Wide-medium | Doorways, driveways, general coverage |
| 6mm | Medium-narrow | Gates, corridors, longer views |
| 8–12mm+ | Narrow / zoomed | Long driveways, perimeter lines, number plates |
The exact field of view also depends on the camera's sensor size, so always check the datasheet's horizontal angle for the specific model.
02Fixed vs varifocal
Fixed lens
Varifocal lens
03Wide isn't always better
A wide lens covers more, but spreads the pixels thinly. At a distance, faces become a few pixels wide. For identification at a gate, a narrower lens aimed at the entry point usually beats a wide view of the whole driveway. See pixel density explained.
04Frequently asked questions
Which CCTV lens size is best for home use?
2.8mm or 4mm suits most homes: rooms, doors and compounds. Use a longer lens for a long driveway or gate.
What does 2.8–12mm mean?
It's a varifocal lens that can be set anywhere from a wide 2.8mm view to a zoomed 12mm view.
Can a lens be changed after installation?
On fixed-lens cameras, no. The camera is replaced. Varifocal cameras can be re-adjusted; motorised ones remotely.
