A varifocal CCTV lens is a type of camera lens that allows for variable focal length adjustment. This means that the lens can be adjusted to provide a different viewing angle, allowing you to zoom in or out on a subject.
Varifocal lenses are often used in security cameras because they provide flexibility in terms of field of view. For example, if you need to monitor a large area, you can set the lens to a wider angle to capture more of the scene. Alternatively, if you need to focus on a specific area or object, you can zoom in to get a closer look.
Compared to fixed lenses, which have a single, static focal length, varifocal lenses offer more versatility in terms of camera placement and scene coverage. However, they are typically more expensive than fixed lenses, and require more adjustment and calibration to ensure optimal performance.
As compared to a parfocal (“true”) zoom lens, which remains in focus as the lens zooms (focal length and magnification change), a varifocal lens is a camera lens with variable focal length in which focus changes as focal length (and magnification) changes. Many so-called “zoom” lenses, particularly in the case of fixed-lens cameras, are actually varifocal lenses, which give lens designers more flexibility in optical design trade-offs (focal length range, maximum aperture, size, weight, cost) than parfocal zoom.