[ solun55 @ 18.04.2016. 08:30 ] @
|How to choose the best lens for your security camera !|
There are many factors that affect the functionality of a camera lens as well as its compatibility with any given security camera. An ill-suited lens can restrict image quality, so before investing in a state-of-the-art security network, one should get acquainted with the qualities that define a camera lens.
Focal length and field of vision
The first specification to consider when choosing a camera lens is its focal length. The focal length of a lens determines both the range and distance of its field of vision.
f = h X D /H
f : Focal length
H: The height of the object
V: The width of the object
D: The distance between the camera and the object
h: The height of the sensor in camera
v: The width of the sensor in camera
The focal length 3.6mm works well for residential or small office surveillance applications.
The basic rule to remember is that a smaller focal length will lead to a wider viewable range. Smaller lenses are known as wide-angle lenses, which produce a greater field of view than cameras with a larger lens. They capture a large area, though objects will appear smaller within the camera image. Wide-angle lenses are designed for monitoring large areas, such as Warehouses, Back or Front Yards and Parking Lots.
Larger lenses, or narrow-angle lenses, have a smaller field of view. They capture a limited area, but objects will appear larger and more detailed within the camera image. Narrow-angle lenses are designed for monitoring a specific target, such as cash registers ,doorways and entrances and objects of value .
In order to maximize image quality, the image format of a lens should match that of its paired camera. All security cameras have an image sensor installed inside of them. These tiny mechanisms are vital to the process of recording objects. Essentially, they take captured light, convert it into electrons then assemble the result into a viewable image. The larger the image sensor, the larger the field of view the camera has.
Format CCTV Lens
Monofocal, varifocal and zoom lenses
Lens types can generally be sorted into three different categories, monofocal, varifocal and zoom. The most basic and least expensive of the group is the monofocal lens. These lenses have a fixed focal length, allowing them to only focus on objects at a specific distance. Varifocal lenses, have a focal length range that the user can manually adjust to alter the range of vision. The most expensive variety is the zoom lens. They are similar to varifocal lenses in that they have a focal length range; however, instead of needing to be manually adjusted, the lenses do so electronically.
A lens’ aperture is the hole that light passes through to enter the camera. The size of the aperture is measured in f-stops, where a lower number indicates a wider aperture. A larger aperture will allow for more light to pass into the camera. The aperture also affects the depth of field. A higher f-stop number and narrower aperture captures more objects in focus, whereas objects viewed with a wider aperture may appear blurry.
The flexibility a camera lens has processing light is dictated by the type of iris it has. The iris influences how much light passes through the lens’ aperture. The two basic varieties of irises are manual and auto. A manual iris allows for a fixed amount of light to pass through the aperture, making it ideal for an indoor conditions with little to no lighting variance. In a situation where light levels are going to fluctuate, like surveying an outdoor environment, an auto iris lens is required.
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