CCTV cameras are becoming an extremely common item in this day and age, they offer protection and additional wellbeing. Choosing the right CCTV Camera lens can sometimes be tough. The information below will grant additional information.
CCTV Cameras This article has been written by Jimmy Johnson. For more information visit http://www.cctvcameralens.net/ CCTV cameras are becoming an extremely common item in this day and age, they offer protection and additional well being. Choosing the right CCTV Camera lens can sometimes be tough. The information below will grant additional information. Closed-circuit television (CCTV) is the use of video cameras to transmit a signal to a specific place, on a limited set of monitors. It differs from broadcast television in that the signal is not openly transmitted, even if it may use point to point wireless links. CCTV is often used for surveillance in areas that may need monitoring such as banks, casinos, airports, services installations, and convenience stores. The use of CCTV in the United States is less common, even if increasing, and generally meets stronger opposition. In 1998 3,000 CCTV systems were found in New York City. Here are 2,200 CCTV systems in Chicago. Crucial Length The crucial length of the lens is measured in mm and directly relates to the angle of view that will be achieved. Small crucial lengths grant wide angles of view and long crucial lengths become telephoto, with narrow angles of view. A “normal” angle of view is similar to what we see with our own eye, and has a relative crucial length copy to the pick up device. Camera Format The size of the camera’s imaging device (CCD) also affects the angle of view, with the smaller devices making narrower angles of view when used on the same lens. The format of the lens, but, is beside the point to the angle of view, it merely wants to project an image which will cover the device, i.e.: the same format of the camera or larger. This also means that 1/3″ cameras can utilize the entire range of lenses from 1/3″ to 1″, with a 1/3″ 8mm lens charitable the same angle as a 2/3″ 8mm lens. The latter combination also provides increased resolution and picture quality as only the centre of the lens is being utilized, where the optics can be ground more accurately. Exposure Control The exposure in a normal photographic camera can be controlled by a CCTV CAMERAS Copyright 2010 combination of close speed and iris opening. This is not so with a CCTV camera lens. A ordinary CCTV camera produces a complete picture every 1/2 of the mains frequency. This is every 1/25 second where the mains frequency is 50 Hz (cycles per second) and every 1/30 second where the mains frequency is 60 Hz. Generally the exposure time is fixed and the only control of the amount of light passing to the imaging device is by adjusting the size of the iris. This is covered in more detail later in this chapter. Most camera tubes and imaging devices have some tolerance of the amount of light passed by the lens to make an acceptable picture. The range of tolerance is generally inversely proportional to the sensitivity of the camera. The more sensitive cameras require greater control of the iris gap. CCTV CAMERAS Copyright 2010
Pages to are hidden for
"CCTV Cameras"Please download to view full document