Safely Crossing the Great Security Video Divide
Get more information about CCTV fundamentals, including digital technology and networking.
Marine scallops (below) can have up to 100 blue eyes working to detect patterns of light and motion. Similarly, the Scallop HD camera has multiple image sensors that stitch together video streams in the camera, with IP network or analog transmission capability.
Mininum Illumination – Referring to the lowest possible light at an object that yields a recognizable video signal, this is often not clearly defined by camera manufacturers. It can be influenced by such things as automatic gain control (AGC) circuitry.
Camera Resolution – This is one of the most frequently quoted and misunderstood parameters of a camera or complete system. Simply, it is measured with the test chart as the number of horizontal lines (vertical resolution) and number of vertical lines (horizontal resolution) that a camera is capable of resolving.
Signal/Noise Ratio (S/N) – A figure that can indicate how good a camera signal can be, especially in lower light levels, this is expressed in decibels (dB) similar to sound performance. Note that a “noisy” digital CCTV picture can reduce compression efficiency and increase storage space. S/N is considerably influenced by temperature.
Dynamic Range (DR) – A very important, yet seldom mentioned, camera specification, DR is similar to S/N ratio, but only refers to the sensor dynamics when handling low to bright objects in one scene. A good image sensor would have a DR of 3,000-6,000:1 or 70-80dB, compared to the human eye, which is 1,000,000:1 or 120dB. This is sometimes referred to as “anti-blooming” sensor chip technology.
Stretching Limits of Images & Signal Transmission
Let’s shift gears from specs and examine a new and exciting type of digital camera technology, a device often called a multisensory panoramic camera. You may remember a similar type of camera I selected for one of my top product picks in 2011. The name of the company was Scallop Imaging and its camera was called the Scallop (see photo). The company has been busy since then refining its product line along with introducing customized offerings.
Instead of one image sensor this camera has five sensors, with each capable of putting high resolution on individual subjects. This is called distributed imaging. The camera then stitches the multiple images together within the camera to save on bandwidth while providing up to a 200° panoramic field of view – this would even allow users to see the wall the camera was mounted on. The cameras provide two video streams for full situational awareness. You get 7-megapixel resolution of individual images or the entire panoramic image of the same high resolution at a lower frame rate. Plus pan, tilt and zoom (p/t/z) capability is available with certain video management systems.
On the transmission front, you may recall discussion of a relatively new HD technology called HD-SDI. While it did allow for sending HD video over existing coax, you had to have very precise termination and signal transmission was limited to around 100 meters. A newer possible upgrade to this HD technology is employing High Definition Composite Video Interface (HDCVI). It is more tolerant of coax termination, can work up to 500 meters, and is very price competitive. The HD-Coaxinator line from SecurityTronix is one HDCVI product you might want to check out. Adding digital cameras to existing analog, coax-based CCTV systems can be intimidating, but with the latest technology at your disposal it can be invigorating too.
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About the Author
Bob Dolph, SSI Contributor
Bob is currently a Security Sales & Integration "Tech Talk" columnist and a contributing technical writer. Bob installed his first DIY home intercom system at the age of 13, and formally started his technology career as a Navy communication electronics technician during the Vietnam War. He then attended the Milwaukee School of Engineering and went on to complete a Security Management program at Milwaukee Area Technical College. Since 1976, Bob has served in a variety of technical, training and project management positions with organizations such ADT, Rollins, National Guardian, Lockheed Martin, American Alarm Supply, Sonitrol and Ingersoll Rand. Early in his career, Bob started and operated his own alarm dealership. He has also served as treasurer of the Wisconsin Burglar and Fire Alarm Association and on Security Industry Association (SIA) standards committees. Bob also provides media and training consulting to the security industry.
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