## How do you calculate the focal length of a CCTV camera?

A simplified calculation for 1/4-inch CCTV lens can be made using the following formula:

- W (horizontal width) = (distance) * 3.2 mm / (Lens Focal Length)
- HorizontalAngle= 2 * arctan(SensorSize/(FocalLenght * 2))
- Watch Video Tutorial.

### What is focal length of CCTV camera?

The focal length (measured in “mm”) of a lens determines how far the camera can see. The most common focal length on security cameras is 3.6mm, which will allow for roughly a 72 degree field of view (FOV described below). This particular focal length works well for residential or small office surveillance applications.

#### How far can a 3.6 mm lens see?

Camera lenses are measured in mm, the smaller the number the wider the angle of view. 2.8mm or 3.6mm would be considered wide angle….

2.8mm lens | 1.5 metres |
---|---|

3.6mm lens | 3 metres |

6mm lens | 5 metres |

9mm lens | 6 metres |

12mm lens | 7 metres |

**How far can a 2.8 mm lens see?**

In general a 5MP 2.8mm lens will offer you around 105° field of view and a 5MP 4mm lens will offer you an 87° field of view.

**How much area does a CCTV camera cover?**

The C-mount cameras come with a detachable lens, which allows users to change it to fit their needs. For instance, the standard CCTV camera lenses can only cover distances between 35 and 40 feet. With C-mount cameras one can use special lenses, which can cover distances beyond 40 feet.

## What is the difference between 2.8 mm and 3.6 mm lens?

A 3.6mm lens is designed to provide an approximate 78° field of view and is the perfect camera in most CCTV applications. Most people think that a 3.6mm lens won’t show a large field of view, but as you can see from the below images, there’s not a huge difference between a 2.8mm and 3.6mm lens.

### Which is better 2.8 mm or 4mm?

Although it has more clarity at a further distance, the 4mm lens shows a similar scene to the 2.8mm. The main difference is the reduced angle of view which gives the illusion that objects are closer to the camera. A 4mm lens is useful for detection & identification.

#### How far can a 2mp camera see?

As I mentioned, the 2-megapixel camera provides a maximum width of 24 ft (7.3 m). Since we cut the triangle in half, the opposite side (O) is equal to 12 ft (3.7 m).