Understanding WDR

Some IP Surveillance cameras offer wide dynamic range to handle a wide range of lighting WDR conditions in a scene. In a scene with extremely bright and dark areas or in backlight situations where a person is in front of a bright window, a typical camera will produce an image where objects in the dark areas will hardly be visible. Wide dynamic range solves this by applying techniques, such as using different exposures for different objects in a scene, to enable objects in both bright and dark areas to be visible.

    

 image with wide dynamic range applied.

image without wide dynamic range

Understand Lux (Light sensitivity)

An IP surveillance camera’s light sensitivity is often specified in terms of lux, which corresponds to a level of illuminance in which a camera produces an acceptable image. The lower the lux specification, the better light sensitivity the camera has. Normally, at least 200 lux is needed to illuminate an object so that a good quality image can be obtained. In general, the more light on the subject, the better the image. With too little light, focusing will be difficult and the image will be noisy and/or dark. To capture good quality images in low light or dark conditions, a day and night camera that takes advantage of near-infrared light is required.

Different light conditions offer different illuminance. Many natural scenes have fairly complex illumination, with both shadows and highlights that give different lux readings in different parts of a scene. It is important, therefore, to keep in mind that one lux reading does not indicate the light condition for a scene as a whole.

Examples of different levels of illuminance

100,000 lux……..Strong sunlight

10,000 lux …….. Full daylight

500 lux ………… Office light

100 lux …………Poorly lit room

Many manufacturers specify the minimum level of illumination needed for an IP surveillance camera to produce an acceptable image. While such specifications are helpful in making light sensitivity comparisons for cameras produced by the same manufacturer, it may not be helpful to use such numbers to compare cameras from different manufacturers. This is because different manufacturers use different methods and have different criteria for what is an acceptable image.

To properly compare the low light performance of two different cameras, the cameras should be placed side by side and be viewing a moving object in low light.

Understand surveillance camera elements

There are a number of surveillance camera elements that have an impact on image quality and field of view and are, therefore, important to understand when choosing a surveillance network camera. The elements include the light sensitivity of a surveillance camera, the type of lens, type of image sensor and scanning technique, as well as image processing functionalities, all of which are discussed in this website.

Some guidelines on installation considerations are also provided at the end.

Light sensitivity

Lens elements

Image sensors

Wide dynamic range

The Core of video Surveillance “Camera”

Cameras are actually the eyes of a video surveillance system. Cameras should be deployed in analytical areas to abduction accordant video.

The two basal attempts of camera deployments are

(1) Use asphyxiates points. 

(2) Awning assets.

Asphyxiate points are areas breadth bodies or cartage charge canyon to reach an assertive area. Examples accommodate doorways, hallways and driveways. Placing cameras at asphyxiate credibility is an actual cost-effective way to certificate who entered a facility.

Assets are the specific altar or areas that charge security. Examples of assets accommodate concrete altar such as safes and commodity areas as able-bodied as areas breadth important action occurs such as bank note registers, parking spots or lobbies. What is authentic as an asset is about to the needs and priorities of your organization. 

 Once you actuate what areas you appetite to cover, there are four camera characteristics to adjudge on:

1- IP vs Analog: The better trend in video surveillance today is the move from analog cameras to IP cameras. While all surveillance cameras are digitized to appearance and almanac on computers, alone IP cameras digitize the video central the camera. While best infrared and thermal cameras are still alone accessible as analog cameras, you can alone use megapixel resolution in IP cameras. Currently, 20% of cameras awash are IP and this allotment is added rapidly.

2- Fixed vs PTZ: A camera can be anchored to alone attending at one specific appearance or it can be adaptable through panning, angry and zooming (i.e., affective larboard and right, up and down, after piece and farther away). Best cameras acclimated in surveillance are fixed. PTZ cameras are about acclimated to awning added fields of angle and should about alone be acclimated if you apprehend an adviser to use actively the cameras on a circadian basis. A key acumen anchored cameras are about acclimated is that they amount 5 -8 times beneath than PTZs (fixed cameras boilerplate $100 - $1000 USD admitting PTZ cameras can be over $500 USD). 

3- Standard Analog vs. Megapixel: This best is agnate to that of TVs. Just like in the customer world, historically anybody acclimated accepted analog cameras but now users are alive into aerial analog cameras. While aerial analog TV maxes out at 3 MP, surveillance cameras can accommodate up to 16 MP resolutions. In 2008, megapixel cameras alone represent about 4% of absolute cameras awash but they are accretion actual rapidly. See an affirmation of megapixel cameras to apprentice more.

4- Color vs Infrared vs Thermal: In TV, a video can be blush or Colors and white. In video surveillance today, the alone time bearing a Colors and white angel makes faculty is back lighting is actual low (e.g., night time). In those conditions, infrared or thermal cameras aftermath colors and white images. Infrared cameras crave appropriate lamps (infrared illuminators) are adequately bargain for bearing bright angel in the dark. Thermal cameras crave no lighting but aftermath alone outlines of altar and are actual big-ticket ($5,000 - $20,000 on average) in day time or a fire areas, blush cameras are the accessible best as the exceptional for blush over Colors and white is trivial. 

 Best organizations will mix and bout a cardinal of altered camera types. For instance, an alignment may use Infrared anchored analog cameras about an ambit with an analog PTZ overlooking the parking lot. On the inside, they may accept an anchored megapixel camera covering the barn and a cardinal of anchored IP cameras covering the access and hallways.

DVR-Based Analog CCTV Systems... become online on internet

DVRs were eventually equipped with an Ethernet port for network connectivity.

This introduced network DVRs to the market and enabled remote video monitoring using PCs. Some network DVR systems in use today enable the monitoring of both live and recorded video, whereas some allow the monitoring of only recorded video. Furthermore, some systems require a special Windows client to monitor the video, whereas others use a standard Web browser; the latter makes remote monitoring more flexible.

The network DVR system provides the following advantages:

·         Remote monitoring of video via a PC

·         Remote operation of the system

Although DVRs provided great improvements over VCRs, they also had some inherent downsides. The DVR was burdened with many tasks such as the digitization of video from all cameras, video compression, recording, and networking. Additionally, it was a “black box” solution, that is, proprietary hardware with preloaded software, which often forced the end user to source spare parts from one manufacturer, making maintenance and upgrading expensive. Virus protection was also difficult to implement. Although the DVR was often a

Windows-based machine, the proprietary interface did not allow for virus protection. In addition, the DVR offered limited scalability. Most DVRs offered 16 or 32 inputs, which made it difficult to cost-effectively build systems that were not multiples of 16, for example, systems with 10 or 35 cameras.

DVR-Based Analog CCTV Systems

By the mid-1990s, the video surveillance industry saw its first digital revolution with the introduction of the DVR. The DVR, with its hard drives, replaced the VCR as the recording medium. The video was digitized and then compressed to store as many days’ worth of video as possible.

With early DVRs, hard disk space was limited, so the recording duration was limited or a lower frame rate had to be used. Due to the limitations in hard disk space, many manufacturers developed proprietary compression algorithms. Although they might have worked well, end users were tied to one manufacturer's tools when it came to replaying the video. As the cost of hard disk space decreased dramatically over the years and standard compression algorithms such as MPEG-4 became available and widely accepted, most manufacturers gave up their proprietary compression in favor of standards — to the benefit of end users.

Most DVRs had several video inputs, typically 4, 16, or 32, which meant they also included the functionality of the quad or multiplexer.

DVR system provided the following major advantages:

• ·         No tapes and tape changes
• ·         Consistent recording quality
• ·         Ability to quickly search through recorded video

Early DVRs used analog monitors such as TV sets for showing video.

However, because the DVR made digital video available, it became possible to network and transmit the digital video over longer distances. This function was first addressed by connecting a phone modem to a serial port on the DVR. Later, the phone modem was built into the DVR itself.

Although the ability to monitor the video remotely via a PC was a great benefit, the actual functionality was not extremely useful because the bandwidth available with phone modems was too low, often in the 10- to 50-kbps range. That meant very low frame rates, low resolution, or highly compressed video, which made the video more or less useless.

VCR-Based Analog CCTV Systems

CCTV system involved the use of analog cameras that were connected to a VCR for recording video. The system was completely analog. The VCR used the same type of cassettes as those sold for a home VCR. Each camera needed its own coax cable to run from the camera all the way to the VCR. The video was not compressed, and when recording at full frame rate, one tape lasted a maximum of eight hours. Eventually, a so-called time lapse mode was incorporated into the VCRs to make the tape last longer. The time lapse mode enabled the recording of every second, fourth, eighth, or sixteenth image. That was how the video surveillance industry came up with such specifications as 15 fps (frames per second), 7.5 fps, 3.75 fps, and 1.875 fps, because these were the only recording frame rates possible in analog systems that used time lapse recording. If several cameras were used, quads became another important system component. A quad simply took inputs from four cameras and created one video signal output to show four different images on one screen; hence, the name “quad.” This invention made the system a bit more scalable but at the expense of lower resolution.

In even larger systems, multiplexers became commonplace. A multiplexer combined the video signals from several cameras into a multiplexed video signal. This made it possible to record even more cameras, often 16 on one device. The multiplexer also made it possible to map selected cameras to specific viewing monitors in a control room. Still, all equipment and all signals were analog. To monitor the video, analog monitors connected to a VCR, quad, or multiplexer.

Although analog systems functioned well, the drawbacks included limitations in scalability and the need to maintain VCRs and manually change tapes. In addition, the quality of the recordings deteriorated over time. The cameras, for a long time, were also black and white. Today, most analog cameras are in color.