How to choose a CCTV Camera Lens?

CCTV Lens Guide including example distances

You need to understand the following when choosing a cctv lens:

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

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". 

F Stop

C or CS Mount

Auto or Manual Iris

Video or Direct Drive

The majority of CCTV Cameras will be able to use both types. Video Drive Lenses contain circuitry which converts video signal from the camera into iris control. Direct Drive Lenses require the cctv camera to contain the circuitry.

A guide to Choosing a CCTV Camera Lens

Example of how different lens sizes can change the viewing angle of a camera.

3.6mm Lens at 5 Meters(16 ft)	12mm Lens at 5 Meters(16 ft)
3.6mm Lens at 10 Meters(33 ft)	12mm Lens at 10 Meters(33 ft)
3.6mm Lens at 15 Meters(65 ft)	12mm Lens at 15 Meters(65 ft)

Example Lens Size Vs Horizontal Field of View

How to choose a CCTV Camera
Lens?

You need to understand the following when choosing a lens:

• 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
  
  

• 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".
  

• F Stop
  
  F Stop or Aperture has 2 measurements. When the lens is fully open (Maximum
  Aperture / Minimum F-Stop), just before the lens completely closes (Minimum
  Aperture / Maximum F-Stop).
  
  F Stop - is the lenses ability to gather light depending on the aperture
  and focal length.
  

• C or CS Mount
  
  The 2 standard cctv camera lens mounts. The difference between the two
  is simply the distance between the lens and the ccd image sensor. C
  Mount - 17.5mm CS Mount - 12.5mm
  

• Auto or Manual Iris
  
  For changing light conditions (e.g. cameras positioned outdoors), Auto
  Iris lenses are needed.
  
  For indoor use manual iris lenses are sufficient as light levels will
  not vary too much.
  

• Video or Direct Drive
  
  The majority of CCTV Cameras will be able to use both types. Video Drive
  Lenses contain circuitry which converts video signal from the camera
  into iris control. Direct Drive Lenses require the cctv camera to contain
  the circuitry.