What is a varifocal lens?

A varifocal lens is designed to provide flexibility in its focal length, allowing users to adjust and zoom in or out as needed. This capability is particularly useful in surveillance applications where capturing a wide range of distances or adjusting to different subject sizes is essential. By being able to change the focal length, the user can achieve various field of views without the need to change the lens entirely. This versatility makes varifocal lenses ideal for CCTV systems, as they can accommodate different monitoring requirements in dynamic environments.

In contrast, fixed focal length lenses remain constant at a specific focal length, offering no ability to zoom or adjust the image size. While low-light capabilities and wide-angle specifications are important features of certain lenses, they do not define a varifocal lens, which is primarily characterized by its adjustable focus.