CCTV buyers Guide

When choosing a CCTV camera system there are many factors that come into play. Here are few issues to consider.

Colour Cameras or Black and White Cameras?

Colour cameras carry an additional premium in price compared with monochrome cameras. But they are also less sensitive making night usage an impractical option unless good lighting is available.
Monochrome cameras can offer Infra Red (IR) sensitivity allowing their use with covert IR illumination possible. This can be particularly useful where planning permission makes extra lighting impractical or the security requirement is such that intruders should not be alerted to the existence of CCTV surveillance.

Indoor/outdoor cameras

If a camera is to be sited outside and is not going to be mounted in an enclosure it must be classed as weather resistant. All of our outdoor cameras are fully weatherproof.

Day/night Cameras

Very popular in domestic and small commercial CCTV applications, day night cameras allow great quality, colour recording during daylight hours. When light levels drop below a certain level the cameraís infra red LEDís allow the camera to continue recording good quality footage even in complete darkness. The distance the cameras will see at night is dependent on the strength of the LEDís.

Lighting Levels

Choosing the correct camera to operate in the ambient light conditions is possibly the most important although most tricky specification to understand.
Light levels are usually measured in Lux. This is a measure of the light energy arriving on an area 1m2 of surface per second.
Typical light levels are:
Full Summer Sunlight: 50,000 Lux
Dull Daylight: 10,000 Lux
Shop/Office environment: 500 Lux
Dawn/Dusk: 1 - 10 Lux
Main Street Lighting: 30 Lux
Side Street Lighting: 0.5 - 3 Lux


The golden rule when deciding which camera to use for a given lighting condition is not to choose one that will only just give a picture. Try to give the camera approximately 10 times its quoted minimum scene illumination. Most cameras will be able to cope with excess light. The major problem is when they do not have enough light to produce a picture.

A monochrome camera rated at 0.05 Lux will produce reasonable results. Colour cameraís need a little more. However, colour cameras achieve good night-time vision by switching to a monochrome mode. You will never get good night-time colour pictures without huge amounts of additional lighting. So think carefully about the added cost of colour over monochrome cameras. As most people are used to colour television it sets a standard so it is very common to still select a colour camera knowing it will switch to monochrome mode at night.


Monochrome cameras respond well to additional IR (infra red) lighting. With this in mind true night-vision cameras include a ring of IR LEDs. Colour cameras also offer IR illumination but as stated previously will switch to monochrome at night even with the IR LEDs turned on. These are true night-vision cameras and are rated at 0 Lux.

Resolution

The value referred to here is the horizontal resolution in TV lines,that is the number of black to white transitions that can be resolved across the image. This is a function of the number of pixels that make up the CCD imaging area and the bandwidth of the camera circuitry. Typical entry level camera resolution is 330 TV lines, with high resolution cameras producing better than 400 lines.

How to display the picture from more than one camera

Most CCTV systems deploy several cameras so a method is required to view and record the images. There are various ways this can be achieved; use a video switcher, a quad processor or a multiplexer. Here are the simple benefits of each system.

CCTV Switchers

A CCTV switcher is a unit that changes between camera pictures one at a time, the output being viewed on a monitor or passed to the recording device. As switchers can use any VCR to record in true real-time, the pictures which are captured can be of a very high quality. The fact that they provide true real-time recording unlike a snapshot from a multiplexer means they provide a superior picture quality. This can sometimes outweigh the disadvantages that switchers can only record one picture at a time.
Advantages - Simple, low cost, good quality real-time pictures.
Disadvantage - Can only record one camera at a time.

Quad Processors


Quad units enable 4 camera pictures to be displayed on a screen simultaneously.
They are useful where it is necessary to monitor several areas at the same time. As with a switcher, what is seen on the monitor is the picture that is recorded on the VCR.
Advantages - Simple to use - shows multiple displays which can be recorded.
Disadvantage - Records only 1 camera at a time real time or 4 at a quarter of the resolution.

Multiplexers

A multiplexer allows simultaneous recording of multiple full-sized camera pictures on to one VCR tape providing more comprehensive recorded surveillance than with a switcher or a quad processor. Most have variable display options such as quad and picture in a picture allowing flexible surveillance of more than one camera at once.
Advantages - Records all camera pictures full size on one tape - gives better monitoring of areas simultaneously - enables large areas to be monitored without losing surveillance due to camera switching time.
Disadvantages - Does not record in real time.

Recording CCTV Images

Time-lapse VCR:
Similar to a domestic VCR but with a slower-moving tape that records the camera pictures as snapshots at split second intervals. The time-lapse can be set to give 24, 240 or 960 hours of recording on standard VCR tapes.


Advantages - very long recording time, cost-effective. Added features like alarms, auto tape-rewind.
Disadvantages - will need a quad processor or multiplexer when recording multiple cameras.
- the longer the recording time the longer the period of time between the snapshots.
- tapes do wear out through use.

PC Based Digital Video Recorder


A PC† with the addition of a video-capture card and surveillance software can be used as a powerful digital system. The purchase of a video capture card and software is a very cost effective method of providing a high specification system.

Advantages
- remote viewing
- software allows many configurations for monitoring e.g. quad display
- records in real time, simultaneously from all cameras
- time and date stamping with motion detect
- alert wizard, send email with photo or video clip,
- SMS alert
- audio alert

Disadvantages
- Software can stop working

Digital Video Recorder

Digital Video Recorder as its name suggests can record images onto a built-in hard drive from one or more cameras. All of our DVRís now come combined with multiplexer functions and are generally considered the future of CCTV recording.
DVRs can generally be split into two groups - standalone black box and PC-based solutions.

Advantages - all-in-one box for recording, multiplexing, alarms and motion detect.
- higher resolution than S-VHS VCR is possible
- near instant access to recording from known time and date
- no loss of quality when copies taken
- can record events in real-time before an alarm actually occurs with \"Pre-event trigger\"
- enhanced playback function, forward and reverse frame by frame playback
- easily connect to networks/internet for remote viewing and playback.

What are the advantages of a DVR?


Before DVRís existed the most common way of recording CCTV video footage was through a multiplexer and time-lapse VCRs. However, DVRís have many advantages over the multiplexer and VCR:


- DVRís can have a huge storage capacity and so eliminate the need to frequently change tapes.
- DVRís donít have problems with tape or VCRís wearing out and so consistently produce higher quality recorded images.
- Because DVRís record digitally, you can retrieve recorded footage instantly rather than scanning through hours of video tape.
- DVRís have motion detection software built-in.
- DVRís can be viewed over a network or the internet allowing them to be used for remote viewing.
- DVRís often work out cheaper than the combined price of a time-lapse VCR, video tapes and a multiplexer.
What should you look for in a DVR?
The number of cameras DVRís can record 1, 4, 8, 9, 16, 32 or 64 cameras at a time.

How long will a DVR record for?


Everybody has different recording needs and many factors affect how long a DVR will record for including: the number of cameras, the compression technology, the frame rate, the picture quality, the picture size, and the amount of recording time required.

What is the maximum frame rate of a DVR?


All DVRís have a maximum frame rate. This simply refers to the maximum number of frames that a DVR can record in one second at any one time. For example: a four camera DVR with a maximum frame rate of 50 frames per second (fps) can record at up to 50fps. If all four cameras are set to their maximum recording rate this will achieve (50/4) 12.5fps per camera. Television is displayed at approximately 25 fps.


The frame rate that is right for you depends on your needs, for example if you are just counting bodies then 1fps will be plenty. On the other hand if you wish to catch people stealing small items from a shop then 6fps will normally be enough.
More advanced DVRís will automatically increase the fps rate on a camera where motion has been detected, providing more footage on an event.

What are the different resolutions on a DVR?


Most DVRís have different resolution options such as 640 x 480 or 320 x 240. The numbers simply represent the number of pixels in the picture (length x height). Higher numbers of pixels means higher clarity on the picture. However, higher numbers of pixels also take up more hard disk space.


What is the compression method used?


DVRís use various compression methods for compressing video footage. This reduces the amount of hard drive space that is used. Additionally, if a DVR can be viewed over the network or the internet a sophisticated compression method reduces the amount of data that needs to be transmitted
Compression methods include Wavelet, MPEG4, JPEG2000, MJPEG and H264.


How do you get video footage from the DVR to the Police?


Being able to easily give video footage to the Police when an incident has occurred is an important part of a DVRís role. Footage can be moved from the DVR to another storage device in a number of ways:


VCR - most DVRís allow you to connect the DVR output to a television connected VCR.
USB - Some DVR's come with a USB connection. This allows footage to be easily transferred onto a PC. If the PC has a CD writer, then footage can simply be burned onto a CD and the CD handed to the Police.
Compact Flash (CF) Card - some DVRís come with the ability to record footage onto a CF card. The CF card can then be inserted into a PC or Laptop and played back.
Networkable Ė DVRís that can be viewed over a network or the Internet via a PC can have their footage recorded straight onto the PCís hard drive. Then footage can simply be burned onto a CD and the CD handed to the Police.
CD writer - the best DVRís come with a built-in CD writer. This allows video footage to simply be burned onto a CD and the CD handed to the Police. The DVR software is also downloaded at the same time, allowing the footage to be viewed on any computer.


Will a DVR send me an email, text message, Pocket PC alert or picture message upon an event?


Most DVRís will send alerts to you when an event (such as motion detection) occurs. Alerts can be sent via email, text messages and picture messages to your mobile phone or your pocket PC.


What does the DVR do if there is a power-cut?


All of our DVRís can be supplied with a backup power supply in the event of power-cut.