CCTV Lens Guide including example distances. You need to understand the following when choosing a cctv lens:

1) Focal Length

The Focal Length is measured in mm.

As a guide:
A short focal length (e.g. 2.5mm) = a wide angle of view;
A long focal length (e.g. 16mm) = a narrow angle of view;
The smaller the CCD Chip - the narrower the angle of view;

2) Depth of Field

The Depth of View is the distance within which objects in a picture are in focus. A large Depth of Field means almost all objects in the Field of View are in focus. A small Depth of Field means only a small section of the Field of View are in Focus.

The following factors can lead to a greater Depth of Field:

• Using a Wide Angle Lens
• High F-Stop
• Using an Auto Iris
• Camera Format

The size of the camera's CCD image device will affect the angle of view. CCTV Cameras come in different chip sizes - 2/3", 1/2", 1/3" and 1/4".