Useful Information
- ♦ Application
- ♦ Cameras
- ♦ Lenses
- ♦ Light & CCTV
- ♦ Number Plate Recognition
- ♦ Thermal Imaging
- ♦ Housings
- ♦ Digital Images
- ♦ Digital Technology & Recording
- ♦ Video Compression
- ♦ Infrared
- ♦ IR & LED Lighting
- ♦ IP CCTV & Technology
- ♦ Monitors
- ♦ Motion Detection
- ♦ Multiplexers
- ♦ PIR Movement Sensor
- ♦ Remote Positioning Devices
- ♦ Video Motion Detection
- ♦ Multiple Screen Display
- ♦ Signal Noise Ratio
- ♦ Survellance Vechicle
- ♦ Three-dimensional (3D) design in CCTV & Security
- ♦ Transmission of Video Signals by Cable
- ♦ Transmission of Video Signals by Remote Methods
- ♦ Transmission of Video Signals by Fibre Optics
- ♦ Video Analysis
- ♦ Wireless CCTV
Lenses
Fixed Focus Length Lens
Fixed focus lenses are the simplest type of Lens, and therefore the cheapest. The presets focal length means a precise calculation is required to select the Lens most suitable for the location, based on the desired size of viewing area and its distance from the Camera. Typical Lens sizes offer either 30 degree view - narrow to allow more detail at distance - or 60 degree, which offers a much wider angle of view.
Varifocal Lens
Varifocal lenses offer more flexibility, allowing the field of view to be adjusted manually. Although more expensive these lenses of popular because the use it is able to get the view required rather than the limited by the constraints of the fixed Lens. Finally, Zoom Lens are the most complex type, offering the greatest functionality once installed - unsurprisingly, Zoom lenses offer the widest choice of associated features and technologies.
Zoom lenses can be remotely adjusted to allow variation of the focal length. This means that a single Lens can be used to view a wide area until an intruder is detected whereupon do it can be zoomed into capture facial details. Generally Zoom lenses incorporate an Auto Iris mechanism to permit 24-hour usage.
Formats
Lenses are also categorised according to size format. As Camera technology has advanced, sensor chips have reduced in size, requiring lenses to produce smaller images at the focal point. This has made smaller lenses possible (less glass resulting in less physical size and weight) although the requirements of precision manufacturing doesn't permit a proportional price reduction - the component materials of a Lens being a very small proportion of the overall manufacturing cost.
The quoted format of the Lens (1", 1/2", 1/3" and now even 1/4") is derived from the ratio of diameter to the viewing image produced. Whilst it is often most cost effective to match the lens format to the camera sensor size, it is possible to use a larger lens on a smaller size camera since the image only needs to be at least as large as the sensor.
Using a larger lens can often be advantageous, since it offers greater depth of field (the range of distances from the lens before objects are too close or too far away to be in focus). Larger lenses also mean that the area of the image that is used is taken entirely from the central, flatter part of the lens causing much less corner distortion and better focus.