CCTV Security Camera News in Da Nang Vietnam

What Are We Looking At: Fixed vs Varifocal Lenses



Much confusion exists regarding the viewing angle and resolution you can receive from an analog camera for your CCTV system.  A big factor is resolution, measured in TV lines (currently offered up to 700TVL), but another factor that weighs in is lens selection.  When you hear the words standard resolution, what does that mean?  Basically, it refers to a 3.6mm lens analog camera with 380 to 480 TV lines.  This class of camera is ideal for general surveillance, and the following chart gives an excellent idea of what to expect.

lens-viewing-angles

With a  fixed lens, the field of view can never change, so what you see is what you get.  The further the image is away from the camera, the less detail.  You are unable to change the lens and thus if you require detail at a distance (but are limited to a specific position or place to mount the camera), then you will need to consider a varifocal lens.  For example, stepping up from a 4mm to 9mm lens will allow you to change the focus without  moving the camera.  The 4-9mm lens option gives flexibility during installation and allows you to customize your viewing area.  A varifocal lens is worth the extra few dollars.