Selecting the Correct Lens
Another characteristic of lenses is the ‘depth of field’ (see illustration). If a lens is focused on an object there will be a certain area of sharp focus in front of and behind the object. The depth of this area of sharp focus is controlled by three factors: the focal length of the lens, the distance from the lens to the object and the F stop.
Lens Format
The lens format relates to the camera format, 1/3 inch, 1/2 inch, 2/3 inch. There are two lens mounting systems. Most CCTV cameras have a ‘C’ mount, although many now use a ‘CS’ mount. ‘C’ mount cameras are not able to use ‘CS’ lenses, however adaptors are available.
To avoid the complexities of lenses with automatic irises, manufacturers have developed ‘electronic shutters’. These achieve the same light adjustment with simpler, fixed iris lenses. The CCD iris common to most Sony CCTV cameras automatically controls image exposure by electronically adjusting the incoming light levels.
Cameras with Built-in Lens
Some cameras are now available with a
For more information contact the Sony Business Information Centre: 01932 816340
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