Video | Fixed Focal-length Lenses
Fixed Focal-length Lenses
As CCTV cameras becomes more reliable and
maintenance-free through the use of solid-state
charge-coupled device (CCD) technology, the lenses
also need to have the same high standards of quality
The range of Fixed Focal-length Lenses meets these
tough requirements by providing long and reliable
operation with no maintenance. Comprising DC-IRIS
and video-iris types, the lens range from wide-angle to
telephoto to cover virtually all applications in CCTV
Designed for easy installation onto a wide variety of
CCTV cameras, they are available for cameras with
1/3-in. and 1/2-in. image sensor formats. The extent of
the range of lenses means that an installer will always
be able to select the most appropriate lens for both
camera and application.
DC-iris and video-iris lenses include manual focus
adjustment types and can be used in applications with
widely varying lighting conditions. These lenses are
available with a standard 4-pin connector.
High quality optics
DC-iris types (direct drive)
Reliable, robust DC-iris mechanism
1/3-inch and 1/2-inch formats
Choosing the correct lens
There is a simple relationship between the required
field of view and the focal length of the lens to be
used (see Field of View figure).
To determine this:
• Estimate or measure the maximum width "W" of the
field of view.
• Estimate or measure the distance "D" between the
camera and the object to be viewed.
• For 1/3 in. lens, use Graph 1 and for 1/2 in. lens use
Graph 2. Find the point on the graph for the lens and
the sensor format corresponding to the "W" and "D"
co-ordinates. To ensure complete coverage of the
object, select the lens indicated by the line above this
object. Normally, for optimum coverage of the field of
view, 1/3 in. and 1/2 in. lens are used with camera
heads with 1/3 in. and 1/2 in. format sensors
respectively. However, 1/2 in. lens may be used with
1/3 in. cameras but the outer areas of the field of
view of the lens will not be seen by the sensor.