For the novice, security cameras choices may seem confusing. One question often asked by customers is what is a Vari-Focal Lens? There are two basic types of CCTV lenses. You can either get a fixed lens, or a vari-focal lens. A fixed lens has a set aperture that cannot be changed. They can be used for overviews or for close up detail, but they cannot be used for both or be adjusted. When you purchase a fixed lens, you will want to use a lens caluculator to make sure you are getting a lens with the correct aperture since you cannot adjust it once you install it.