Surveillance Hardware

To perform video surveillance, you'll need the following,

Video Cameras: For the purpose of capturing videos.

Display Monitor: A display monitor for a user or a security staff to monitor the surveillance site in real-time, and for viewers to see the recorded video clips. The monitor can be a professional surveillance monitor, a TV, a computer monitor or a small LCD screen.

Storage: A traditional VCR, a Digital Video Recorder, a computer or other Video Storages for backup and search purposes.

Power supply: Power Supplies for both Video Cameras and storage device.

Cabling: For most CCTV cameras, it requires proper cabling between video cameras and the storage device. The most commonly used CCTV cables are coaxial cables (RG59, RG60) and Ethernet cables (CAT5, CAT6).

How to select Security Cameras?

Type	Picture	Usage	Installation & Remarks
Dome		Due to its unobtrusive nature, Dome Cameras are frequently used in offices, stores, homes and elevators.	Dome cameras are mostly installed indoors on the wall or on the corner of the ceiling.
Bullet		The size of a bullet type camera is similar to a dome type camera. Most bullet cameras are designed to be water-proof, and some are even weather-proof, that could sustain stressful temperature changes. However, that also contributes to their relatively higher prices.	It normally comes with a small bracket attached, and is applicable for outdoor installation.
Standard / Box		The good old box type camera is good at thwarting crime intentions. It is normally more conspicuous in both size and shape. Box type cameras are more flexible in adapting lens of different focal lengths for optimum zoom of the surveillance targets.	A box camera would need a bracket for installation. And rain-cover housing is required for outdoor installation.
Covert		A covert camera, or hidden camera, is designed to be invisible or is disguised as another object such as a smoke detector or a motion sensor.	Installing and operating covert cameras would incur privacy infringement concerns. In general, it requires consent from the recorded persons.
PTZ/ Speed Dome		A PTZ camera can Pan and Tilt the direction of the camera and zoom the focus to track the surveillance target through a remote control panel or through a DVR.

The good old black and white security cameras are gradually replaced by the color ones. However, for most of the mid-end color cameras with night vision feature; their color image will turn into black & white when night vision is activated under dark environment.

Modern Night Vision cameras are mostly utilizing the Infrared technology. Among them, IR cameras are the most commonly found. The idea is to combine illumination of infrared spectral range with CCD sensor sensitive to this light. The resulting scene is a monochrome image. That explains why a color IR video camera will turn into monochrome one when IR is activated. Though, adding an IR filter could enable night vision for a Video Camera, it also inflicted a side-effect that introduces some minor color change on the color videos.

Another Night Vision Video Camera called ICR (IR Cut Removal) Camera is designed to solve the aforementioned problem. Due to their ability to possess night vision while retaining the true color nature under sufficient ambient light, they are also called True Day and Night Cameras.

The last Night Vision video camera we'll introduce is Day and Night Color Video Camera. As the name implies, the camera is able to take true color images at very low luminance level, such as 0.0003 Lux or lower. The designs are either using larger image sensor or using sensor with higher sensitivity or both. Thus, Day and Night Color Video Cameras are inevitably more expensive and are used in special applications.

The criteria in defining whether a video camera is Analog or Digital, depends on its output signal format. Since the traditional backbone of surveillance device are VCRs which takes analog inputs, most surveillance cameras are designed to output analog signals. Thus, even when the technology has evolved into digital era, the most commonly found cameras still output analog signals, even though its back-end image processing mechanisms are mainly in digital form. Before sending out the signal, it converts its digital signal into analog one to comply with the VCR's input format.

The analog video camera follows the same transmission standard of either NTSC or PAL as the traditional analog televisions does. Thus, no matter how high its image sensor resolution is, the resulting output signal is still constrained within 720 x 480(NTSC) or 720 x 576(PAL). On the other hand, the digital video camera doesn't have such constraint and is free to expand its resolution as long as the technology can support.

Does surveillance camera record sound at the same time?

Most Video Cameras are not equipped with sound recording feature. Besides privacy concerns, the recorded sounds are not very practical in identifying the suspects in a scene. However, some covert cameras do support sound recording features, and they are mostly used in a detective surveillance purposes. And since most of the Video Recorders do support at least one Audio-In channel, user can purchase a multi-directional microphone to do the recording.

How do I record surveillance videos? What kind of equipments do I need?

A video camera itself does not record video. To record all or part of the surveillance videos, you'll need a video recorder. The Digital Video Recorder, or DVR, is currently the mainstream video recorder in the surveillance industry.  DVRs can be further divided into standalone DVRs and PC-based DVRs.

A standalone DVR is designed to record video streams from multiple video cameras. Its basic function is to capture video frames streamed from the video cameras, display them on a screen for real-time monitoring, compress the captured data and store them in a disk drive, USB memory stick or SD memory card or other storage devices. The number of video-in channels ranges from 4, 8, 9 to 16 or more.

A PC-based DVR is a Personal Computer with one or more video capture cards. Each capture card is able to support 4, 8 or more video channels depending on the video capture card capacity.

Compared to PC-based DVRs, standalone DVR requires less maintenance and simpler setup. However, unlike the versatility of PC-based solutions, standalone DVRs' functions are barley changeable.

What is a Network DVR?

A DVR with networking capability is called a Network DVR. Nowadays, the mainstream DVRs are mostly equipped with networking capability. With a Network DVR, user can access the DVR either locally with panel buttons and remote control, or remotely through the PC web browser.

What is an IP Camera?

An IP Camera or network camera is basically a digital camera embedded with Internet Protocol Module and a web server. Thus, after connecting it onto the network, it acts like a combination of a video camera and a Network DVR without storage. User can use a Web Browser to view the captured video and control its Settings.

The IP camera inherited the advantage of digital video camera in its flexibility of resolution expansion. However, it also comes with higher cost compared to an analog video camera.

What does Illumination stand for? What is Resolution?

Illumination is the measure of the intensity of light. For a video camera, the lower the illumination requirement the better it is in accepting low ambient light images. The unit of illumination is Lux. A regular day type video camera's minimum illumination requirement is at around 0.1Lux to 1Lux.

The Resolution of a analog video camera is defined by the term TV Lines (TVL). An introduction of the TV Lines measurement can be found here. Normally a higher TVL value means better video quality. However, since TVL is difficult to verify, it is a relatively good guidance to check on its image sensor resolution which is calculated in pixel counts. For example, under the same condition, an image sensor with pixel count of 771 x 494 would produce better image quality than a sensor of 580 x 470 pixel count.

What's the difference between CCD and CMOS image sensors?

An image sensor is a device that was used to convert optical images into electronic signals. Nowadays, CCD and CMOS are the two most commonly used technologies to do the conversion.

The major advantage of CCD sensor is that it outperforms CMOS sensors in its light sensitivity. Moreover, its early maturity of technology also makes it the dominant image sensor utilized in the video camera industry.

A CMOS sensor, also known as Active Pixel Sensor (APS), consumes less power than a CCD one. Though, a late comer regarding to its development history, its prevalent applications in the IC industry and hence lower manufacturing cost is pushing it fast forward to become the next generation image sensor in the coming years. Yet, currently, most CCD video cameras still outperform their CMOS counterparts in the performance of the color image presentation, especially in low light conditions.

What is BLC?

BLC is the acronym of Backlight Compensation. When taking an image of an object, if there is a strong back-light in the scene, the object will be darker than it actually is, i.e. underexposure. This is because the video camera calculates and adjusts its light exposure according to the average amount of light source detected. When there is a highly contrasting light source in the scene, the average will be shifted upward, and in response, the camera will lower its exposure. Thus, BLC is designed in a way that when the video camera detected a highly contrasting light source in a scene, it automatically increased the exposure by a predefined amount.

Although BLC can solve the underexposure problem, the increased exposure also leads to the overexposure of the strong light area. A quick fix to this problem is to arrange the video cameras in a way that each one covers an area with similar light intensity, for instance, one camera for indoor surveillance, and the other one for outdoor surveillance. Moreover, a technology called Wide Dynamic Range (WDR) is introduced to solve this problem.

What is AWB?

Auto White Balance (AWB) is a technique to correct or to improve the color of a scene by manipulating the intensity of the basic RGB color elements. Its purpose is to make the scene more natural and appealing to viewers.

Image captured without white balance	Image after white balance

What is AES? What's its difference with Auto-Iris?

AES is the acronym of Auto Electronic Shutter. An Automatic Electronic Shutter controls the duration at which image sensor is exposed to the light. It determines the exposure time and helps delivering the best quality video by dynamically adjusting for the current light conditions by diminishing exposure in a bright situation and extending exposure in a low light situation.

Basically, Auto-Iris does the same work of adjusting light exposure for video cameras. And since it requires a motorized lens, its cost is higher than an AES design. However, there are two advantages in the Auto-Iris design, namely the depth of field and the elimination of smearing effect.

An AES camera works with fixed iris lens. And since a CCTV camera wants to maximize low light performance, its iris is wide open and the depth of field is shortened. Furthermore, the smearing effect caused by CCD sensors can be avoided by Auto-Iris's motorized lens.

What is Wide Dynamic Range?

Wide Dynamic Range, also known as WDR, is designed to solve the overexposure or underexposure problems encountered in the highly contrasting light condition, namely when there are very bright and very dark areas coexisted in one scene. Moreover, WDR also reduces the blooming and smearing effect found in CCD type video cameras. Nevertheless, the superior video performance of WDR cameras is also accompanied by significant cost increase.