A varifocal lens has an adjustable focal length range, so the field of view can be set on site and changed later without replacing the camera. It suits cases where the exact coverage is not known in advance or a view needs tightening after installation.
A fixed lens commits to one field of view at purchase. A varifocal lets the decision be made at the ladder, which is often the better moment to make it.
Adjusting and locking it down
The lens is zoomed and focused by hand, then the rings are locked. Once set, a varifocal behaves like a fixed lens, so record the chosen focal length so a replacement matches.
Where it fits
Long corridors, gates and sites under renovation benefit from on-site adjustment. A carefully chosen fixed lens is usually smaller, less expensive and more stable where the view is already known.
Related:Commercial security camera systemsGlossary: PTZ camera systems