The right lens for every situation

Lenses form a unit with the camera. They are decisive for the performance of a surveillance system and the quality of the recordings. ABUS has the right lenses on offer for all requirements: There are interchangeable lenses for cameras, as well as camera models with lenses already integrated. Your specialist dealer will be happy to help you when choosing the right solution – tailored to the camera's application and your special requirements.

Calculating focal length

When choosing the right lens, you should start by finding out how far away the camera is from the object being monitored, and how wide the area is you wish to keep an eye on. This information will allow you to calculate the appropriate focal length of the lens. The range of focal lengths to be covered by zoom cameras is calculated from the varying widths of the surveillance area, e.g. a façade which is 5 meters wide or the 1 meter wide front doors.

This example shows you how easy it is to calculate focal lengths for lenses with a 1/3" image sensor.

Example focal length calculation

The view through the lens

Our interchangeable lenses are fitted with particularly high-quality aspheric lenses, which have extraordinarily good optical properties and generate no blurred edges.

The lens bundles the incoming light to generate a sharp picture, forwarding it to the CCD or CMOS image sensor. The CCD/CMOS chip converts the light into a video signal. The better the lens conducts the light into the camera, the better the pictures will be.


When spherical lenses are used, changing the focus makes parts of the picture become fuzzy.


With aspheric lenses, the focus does not change, so you get a sharply focused, light-adjusted picture.

Variable or set

Lenses can be adjusted for every requirement. Special lenses with an auto-iris function adapt perfectly to the incoming light at any time of day.

Using variofocal lenses, the focal length and therefore the angle of view, or surveillance area covered by the camera, can be varied and adjusted. The focal length is changed manually when the camera is installed and cannot – in contrast to zoom lenses – be controlled using software or remote access.

On fixed lenses, the focal length and therefore the angle of view are defined at a certain value, and cannot be changed. The advantage over variofocal lenses is the lower price, however at the expense of less flexibility in use.

Questions & answers

Security glossary