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
Given light in the correct quantity, quality and emanating from the right direction, the modern CCTV camera is capable of minor miracles in terms of its ability to record events, aid identification and enhance our lives in a myriad of ways, not least the provision of surveillance and security.
Conversely, if it is starved of those three simple elements, even the most expensive and technically advanced camera will struggle or fail to produce the results expected of it. For a CCTV camera 'fighting light' can all too easily become a fight for life - both operationally and commercially. With just a little more consideration and some small adjustments to our system design and installation practices we could ensure that far more of our many CCTV systems were functioning to the best of their very remarkable abilities.
The colour rendition of many types of everyday environmental lighting is another rich source of potential - and often conflicting - problems. For example, in a perfect world, the hard pressed camera sensor might choose to exist in a flood of metal halide (HPI) light. This form of lighting, which is often found at airports, docks and similar facilities, produces a cool clear white light with excellent colour discrimination - perfect for the camera. And yet there is trouble in paradise! In this case the 'fight' can be against the existence of too much light for the comfort of the community.
Light pollution is a legitimate concern where metal halide is employed so much consideration must be given to mitigating this negative effect through shielding and careful design if such technically superior systems are to be encouraged. At the other end of the scale low pressure sodium (SOX) is a highly efficient monochromatic light with a yellow tinge which has low running costs and is thus used mainly in street lighting. It is not, however, capable of colour discrimination so most objects in its presence appear as shades of grey.
Monochrome cameras which outperform colour cameras in terms of low light ability and resolution or specialist day/night cameras can switch between colour and monochrome operation as lighting levels decrease are the 'order of the day' in these circumstances. CCTV consultants, specifiers and end-users should be discouraged from unnecessarily pitching expensive colour cameras into a fight they cannot win! High pressure sodium (SON) is an excellent compromise and is the dominant light source for lighting over long periods. It has an efficient golden white light source and is capable of good colour rendering. The 'fight' here is to persuade our local authorities and others to extend its use where CCTV coverage is deemed important.