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How to choose a CCTV Camera Lens
This is a guide on choosing a CCTV Camera lens and some considerations that should be taken into account when doing so.
CCTV Lens Guide including example distances
You need to understand the following when choosing a cctv lens:
The Focal Length is measured in mm. As a guide:
a short focal length (e.g. 2.5mm) = a wide 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.
The following factors can lead to a greater Depth of Field:
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 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).
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.
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.
CCTV Lens Calculator
For a quick 1/3″ CCD Camera you can work out the lens required using this simple method:
d x 4.8 / A = L
20 x 4.8 / 5 = 19.2
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