Posts Tagged ‘ fixed lens’

What is a Varifocal Lens?

Written By:
Sunday, November 29th, 2009

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.

A Vari-Focal lens is usually more expensive, but it allows you to adjust the aperture on the fly. This leaves less room for error and would also allow you to make changes to the view at a later date. Varifocal lenses come in various apertures. These are the general lense sizes. 2.8-12mm lens, 3.5-8mm lens, 6-60mm lens, and 5-100mm lens. The larger the aperture number, the more zoomed in the image will appear and the greater detail that can be captured. The smaller the aperture number, the wider the view and less detail will be captured. Keep in mind that all lenses have a give or take. The larger the aperture, the greater the detail, but you will get less of a field of view, so the image will be narrower. The smaller the aperture, the wider the field of view, but the less detail you will get.