What is CCTV?
Closed Circuit Television (CCTV) is a system where the circuit in which the video is transmitted is closed and all the elements (camera, display monitors, recording devices) are directly connected. This is unlike broadcast television where any receiver that is correctly tuned can pick up and display or store the signal. Such specialized systems are not subject to regulation by the Federal Communications Commission (FCC); however, security cameras using scrambled radio waves are in fact subject to common carrier tariffs and FCC conditions of service. In the past, these signals would be transmitted to a monitor equipped with a videocassette recorder, but these have been all but totally replaced by digital video recorder (DVR) systems that can store far more video and back up data automatically.
What is CCTV Used For?
The most common use of CCTV is in security camera systems. They’ve been found for years in areas like large retail shops, banks, and government institutions. Thanks to reduced costs in the manufacture of cameras and video recording equipment, camera systems are becoming more and more commonplace in smaller businesses, and even private homes.
Other Uses of CCTV
CCTV has become ubiquitous in large cities, along major highways, and areas that host large events. On streets and roads, CCTV is often used in traffic law enforcement, but it’s used to monitor traffic patterns, allowing emergency services to react quickly to accidents and for maintenance departments to better plan necessary construction projects. In hotels, stadiums, and convention centers, CCTV is often used in private television networks, broadcasting sporting events or special events throughout their facilities.
Most airports and train stations throughout the world have installed security cameras connected to CCTV systems with the goal of combating terrorism. These video feeds are constantly monitored by local and international law enforcement agencies in an effort to keep travellers safe.
Any camera that broadcasts a signal can be attached to a CCTV system, whether it’s wired or wireless, but they are most often associated with high-end surveillance cameras. Pan/tilt/zoom (PTZ) cameras allow a user to remotely control a camera. The type of lens used will depend on the application and area the camera will be installed Fixed aperture lenses cannot be adjusted for distance or lighting considerations. Lower in cost than other lenses, these are usually sufficient for indoor installations where lighting will be consistent. There are two types of adjustable iris lenses. Manual iris lenses can be adjusted for changes in lighting conditions, but it must be done manually. Auto iris camera lenses can sense changes in lighting in the area they observe and will automatically make adjustments so they provide the best picture possible. These are usually the best choice for outdoor installations. Manual zoom lenses allow you to adjust the focus area on a camera by hand. If you want to be able to change focus remotely, motorized zoom lenses are also available, but more costly. A third type of zoom lens, automatic zoom, can automatically focus on objects moving within their view.
CCTV Systems and Hidden Cameras
Hidden cameras can be integrated into any CCTV network, and often are. They allow users to record criminal behavior when criminals are on the lookout for standard security cameras. They can be more effective in capturing video evidence, since they are harder to avoid, but sacrifice the deterrent properties of traditional CCTV cameras. On the other end of the spectrum, dummy cameras are a low-cost deterrent device, appearing to be CCTV cams, often complete with blinking lights. Many small businesses use dummy cams as an extra measure of security.
Tips on CCTV Security Camera Lens selection
How to select a proper security camera lens in 3 easy steps and save money doing it?
1. Should I use Manual Iris, Auto Iris or DC lens?
- You can save money and use manual iris lens only when scene illumination never changes. Example: illuminated store or office.
- If the light changes a lot it is recommended using auto-iris.
- Guide: smaller the focal length number => wider is field of view.
- If you have securit camera in the office or warehouse and you want to see as much as you can, you should go for 2.8 or 4 mm lens (makes wide, somewhat distant view)
- If you want to observe limited area, like entrance you should go for 8mm or (makes narrow view and objects are closer).
- Give us a call and we can help you determine what security camera lens will best suit your location.
- Use varifocal lenses to get flexibility for choosing best field of view.
The CCTV security camera lens chart and field-of-view diagrams are designed to assist you in selecting the right lens size for your application. Please contact us if you require additional information or assistance. Keep in mind all of the security cameras we sell come equipped with lenses that will achieve 95% of your surveillance applications.
CCTV Lens LUX ChartCCTV Lens LUX Chart
During the day the amount of illumination reaching a scene depends on the time of day and atmospheric conditions. Direct sunlight produces the highest-contrast scene, allowing maximum identification of objects. On a cloudy or overcast day, less light is received by the objects in the scene, resulting in less contrast. To produce an optimum camera picture under the wide variation in light level (such as occurs when the sun is obscured by clouds), an automatic-iris camera system is required. Typically, scene illumination measured in foot-candles (ftcd) can vary over a range of 10,000 to 1 (or more), which exceeds the operating range of most cameras for producing good quality video images. The chart above summarizes the light levels occurring under daylight and these low light level conditions. The equivalent metric measure of light level (lux) compared with the English (ftcd) is given.
The following chart displays the comparison of CCTV lens with the regular 135mm film camera lens.