Choosing the Camera Lens: Affect of Camera Height and Lens Size on Counting Area Size
We normally supply cameras with a 3.6 mm focal length lens. This is suitable when the distance between the floor and the camera is 2.5 to 4 metres. However, we can supply other lenses for other floor-to-camera distances. The following table shows how wide the counting zone will be for various focal lengths and camera heights. You can extend the size of the counting zone using the VT Setup software. The zone size can be altered by up to 1.25 times for a single camera. For wide entrances covered by multiple cameras, use 0.9 times the standard width to calculate the separation between cameras.
Zone Width in meters by Camera Height and Lens Focal Length
In this table the height the camera is positioned above the floor is shown down the left hand side in metres. If you then look right, along the row, you will see the default zone width for a range of possible lens focal lengths. Remember, you can change the zone width by up to 25% with the VT Setup Software.
| Focal Length > | 2.9 mm | 3.6 mm | 4.6 mm | 6.0 mm | 8.0 mm |
| Height | |||||
| 2 m | 1.66 m | ||||
| 2.5 m | 2.07 m | 1.67 m | |||
| 3 m | 2.48 m | 2.00 m | 1.57 m | ||
| 3.5 m | 2.90 m | 2.33 m | 1.83 m | ||
| 4 m | 2.67 m | 2.09 m | 1.60 m | ||
| 4.5 m | 3.00 m | 2.35 m | 1.80 m | ||
| 5 m | 2.61 m | 2.00 m | 1.50 m | ||
| 5.5 m | 2.20 m | 1.65 m | |||
| 6 m | 2.40 m | 1.80 m | |||
| 6.5 m | 2.60 m | 1.95 m | |||
| 7 m | 2.10 m | ||||
| 7.5 m | 2.25 m | ||||
| 8 m | 2.40 m |