This is the number of horizontal lines a camera can record and if you`ve done a bit of research already, you would be forgiven for thinking it's the holy grail of camera quality. It isn't.

Of far more importance is ensuring the correct lens for your particular application. No amount of TVL will allow a particular lens to capture detail beyond it's natural ability. At D1 resolution you have a given number of pixels (around 400,000) and you need the lens to concentrate sufficient pixels onto the subject to allow you to capture detail. If a 380TVL camera allows you to read a number plate at 15 metres for instance (probably around a 22mm lens) then a 700 TVL camera with the same lens wouldn't be able to read it at 20 metres. It might manage an extra half metre or so but that's it. In the detailed description for every camera we indicate typical detail capture ability based on how far away you should be able to read a car number plate because everyone knows what a number plate is and you either can read it or you can't. If a competitor is suggesting far greater ability for a given lens then don't hold your breath. You won't be reading plates at 25 metres with a 9mm lens no matter how many TVL!

The final thing to keep in mind is that many figures quoted are untrue or misleading. A number of the UK national retailers are currently claiming a TVL resolution for their cameras which is in fact only achievable in black and white at night. The daytime colour resolution is less than the figure emblazened across their websites and publicity material !

In the pictures below note how the actual number of TV lines makes very little difference, it`s choosing a lens that fills the screen with your chosen subject that makes the difference.

420 TVL camera with more powerful zoom lens	540 TLV camera with less powerful zoom lens

Zoom or varifocal CCTV camera lens

The best bet is to go for cameras with a zoom lens. You`ll pay a little bit of a premium over a fixed lens camera, around £20-£30 pounds or so depending on the exact lens but it means you have more flexibility over a fixed lens camera. Once you've got the camera in place you can zoom in or out to best suit your needs.

Pro and Diamond Sony electronic Packs - our choice of electronics

After loads of testing and evaluation we have come up with 2 different packages for the camera`s internal electronics. There are lots of factors to consider and not just the obvious. The photos below show 2 different Sony HQ1 packages we looked at, the actual infra red light available is the same in both images, it`s just the camera`s electronics that differs.

Pro spec Sony electronics pack

A great electronics combination based round a Sony 1/3 inch  CCD and Sony digital signal processor chipset (DSP). Where this package really scores is in its low light capability down to as low as 0.01lux. Which also gives superb infra red performance. For most applications this package will be more than adequate.

Diamond spec Sony electronics pack

Our best combination again based around  a 1/3 inch Sony CCD and with a high specification DSP. This provides the equivalent of around 650 tvl definition and unlike most 500+ tvl cameras still allows for good low light filming down to 0.05 lux. The result is slightly clearer images. It isn`t night and day between the Pro and Diamond packs but there is a definite improvement. For applications where you want the very best possible results. As ever call us to discuss your individual needs.

Our Pro Sony electronics pack	Our Diamond electronics pack

My local DIY superstore and ebay sell CCTV packages that look great value for money

Quite a lot of places sell CCTV these days and you`ll often hear retailers such as us putting down "one box solutions" sold by the out of town retail giants and on "the bay". It`s all well and good for us to claim our products are better, but what does "better" mean.

We`ve done a little comparison below using our cheapest camera with a camera included in a CCTV kit. Ignore the fact that the CCTV kit camera is black and white - we were actually doing them a favour because black and white cameras generally have a higher resolution and give a clearer image than colour cameras.

Camera bought from a DIY chain	Our cheapest camera

A quick word on camera basics

As with the human eye light enters the camera through a lens, it then hits an electronic sensor, the equivalent of our retina. This sensor turns the image into an electronic signal. The electronic signal goes to a processor called a DSP or "chipset" where it is processed and adjustments made for different light conditions, the DSP does the same job as our brain in the human eye comparison.

 

CCD and CMOS sensors - the camera`s retina

There are 2 types of camera sensor. CMOS (short for complementary metal oxide semiconductor), sensors require a lot more off chip circuitry to clean up the image if you want a high quality result. Costing less to produce CMOS sensors offer a cheap solution at the expense of quality for lower resolution applications. CCD sensors (short for charge coupled device), are more expensive to produce but the image quality is generally higher needing less electronic "touching up". Most professional cameras tend to use CCD technology.

 

1/4 inch or 1/3 inch CCD Sensor - why 1/3 inch is better

This measurement refers to the size of CMOS or CCD image sensor used in a camera. Smaller image sensors are less sensitive to light and are more likely to suffer image deterioration or "noise". 1/4 inch sensors measure 7.68mm² (3.2mm by 2.4mm). 1/3 inch sensors measure 17.28mm² (4.8mm by 3.6mm). So a 1/3" sensor is 225%  the size of a 1/4" sensor - a significant increase. Try to buy cameras with 1/3 inch sensors, particularly at the lower end of the market where manufacturers will be fitting cheaper DSP or chipsets.

 

DSP (sometimes called the chipset) - the brain of the camera

The type of processing chipset or DSP is equally as important as the CCD sensor. We have worked very hard with manufacturers to come up with the best combination to suit individual cameras. Ability to film in low light levels, how adaptable the camera is to different lighting or climatic conditions and ease of use are all affected by the choice of DSP. A lot of manufacturers go way overboard when packing DSP based features in their cameras to the point where even professional installers don`t fully understand them. We like a nice simple "does what it says on the tin" solution with settings automatically selected by the camera where possible.

A word of warning: we see many non genuine sensors and chipsets where the original manufacturer's name is removed and replaced with a brand name such as Sony. We work hard to ensure trace-ability of all components within our cameras. We do this by selecting manufacturers very carefully. It helps greatly that we travel to the far east ourselves to deal directly with manufacturers.

Lux Levels - how well a camera performs in low light or infra-red light

This refers to how much light is required for the camera to be able to "see". We have chosen Sony CCD and DSP combinations which ensure the vast majority of our cameras can see down to 0.01lux without infra-red lighting. Their sensitivity also ensures superb results when used with a camera`s built in infra red lighting. When evaluating cameras we notice massive differences in low light performance.

Some cameras artificially "boost" light levels but take these figures with a pinch of salt. The resultant images at maximum boosted levels are very poor because as well as boosting the subject they also amplify "noise" and other unwanted parts of the image so take these ridiculously low lux figures with a pinch of salt.


These pictures show how well our Pro Sony electronics pack 0.01 lux cameras perform in low light conditions

What the human eye sees	What our 0.01 lux cameras see

These photos are not a trick, our 0.01 lux cameras really do perform that well, to the extent sometimes when you leave the office after looking at the CCTV monitor you are shocked at how dark it`s become outside !

Lens focal length (measured in mm) - The most important thing to get right when selecting a camera

This refers to the focal length of a lens, not it`s diameter. The smaller the number the wider the field of view and also the more light it lets in. The bigger the number the narrower the field of vision, the more telephoto it becomes, (like a pair of binoculars) and the camera is able to detect a higher level of detail. With a 1/3 inch CCD camera 4mm or less would be considered wide angle, 9-10mm or more telephoto. Remember that wide angle lenses provide greater area coverage but at the expense of detail. A longer, more telephoto lens can show increased detail but only a limited area.

Zoom or vari-focus lens - The easiest way to make sure you pick the right camera

This is where the focal length of a lens can be altered to change it from a wide to a narrow, more telephoto setting. Their versatility makes optical zoom lens cameras a natural choice for self installation as you can zoom in or out to best fill the frame with your image once installed.

Optical and digital zoom - know the difference

With optical zoom the lens itself is doing the work and the detail quality of the subject will increase.

With digital zoom the enlargement is done by electronically expanding a section of the image. This comes at the expense of quality to the point often where the image becomes unrecognisable.

Optical zoom	Digital zoom

Brand - Sony etc

In the CCTV world this will refer to the manufacturer of the image sensor (CCD or CMOS). The choice of brand will determine quality, lifespan and level of technical development. We are big fans of Sony believing their product to be at the cutting edge of market technology. It is also important that the image sensor is supported by a good DSP or chip set to process the signal.

Different types of CCTV cameras

These are cameras designed to be mounted either inside or outside and incorporate built in Infra red (I/R) illumination. As light levels fall the Infra-red lights switch on automatically and the camera changes from colour to black and white. Black and white cameras require less light to work and respond to Infra-red lighting.

Probably the most versatile of all the cameras on the market they are very easy to mount and adjust. All our cameras feature sturdy metal brackets which can be locked in place with an allen screw. They are often referred to as day - night cameras because of their ability to film in total darkness as well as normal daytime conditions.

Shaped, how did you guess, like a bullet these don`t come with infra-red illumination and tend to be used for slightly more discreet purposes due to their less intrusive appearance. You will often see them used to monitor service counters, till positions or other distinct areas. Many cheaper bullet cameras use the smaller 1/4 inch image sensors, often with CMOS sensors. All our bullet cameras come with larger 1/3 inch Sony CCD sensors. Being all metal construction they can be used in reasonably hostile environments. Our bullet cameras are also extremely sensitive working to light levels as low as 0.01 lux.

 

As the name suggests, small cameras that are easy to tuck away somewhere out of sight or cameras that are disguised as another object such as our PIR detector camera. Don`t be fooled by the small size, our covert cameras are professional quality Sony 1/3 inch CCD items. There are a lot of "gimmick" covert cameras sold which feature vastly inferior electronics

These are the type of camera you would traditionally associate with CCTV. Not the best looking camera in the world, they need a special housing if you want to protect them from the elements, are more prone to damage and can sometimes take a bit of setting up. Camera bodies and lenses are usually sold separately. Not the easiest camera to self install so for this reason we don`t sell them.

 

Power and Video connections - don`t worry, we`ve got it covered

All our cameras comply to current industrial standards in terms of connector types. Video connection is via a BNC connector, power via a DC plug. Any camera purchased on this site will work with any camera lead purchased on this site.

 

The following is a list of technical terms sometimes associated with CCTV cameras. Do not use it as a check-list when buying cameras, there are far more important factors to consider and to be honest we`ve already taken care of things when selecting which cameras to stock. We include it more to satisfy curiosity than anything else.

AGC
Automatic Gain control. This allows the camera to maintain consistent images in varying light conditions. Different times of the day and different times of year will provide dramatically different lighting. AGC ensures a consistent image.


AES
Automatic electronic shutter. If you think of a normal stills camera to take a picture you adjust the shutter speed to vary the amount of light entering the camera. In bright light you need a fast shutter, in low light you need a slower shutter. With a CCTV camera  you don`t have a physical shutter but an electronic equivalent. The longer it`s "open" the more light that enters but also the more blurred the image.


BLC
Back light compensation. This is a clever feature that helps even out an image. Imagine you were standing in front of a window and someone took a photo of you. The camera would either choose you as the subject and the outside of the window would appear pale and washed out, or it would choose the outside as the subject and you would be too dark. Back light compensation helps avoid this and evens the picture out.


CDS sensor
This one is a bit of a cheat. Some places quote CDS as helping cameras see in low light levels. It`s just the photo-cell which turns the Infra Red lights on, so every camera with Infra Red lighting built in will have a Cadmium Sulphide sensor! It`s just a light switch and nothing to do with the camera CCD sensor or it`s associated processing circuitry.


Infra-red lighting
Some of our cameras have built in infra-red lighting. At low light levels the small led`s switch themselves on and the camera switches to black and white mode. You can`t actually see infra-red lighting with the human eye (although you will notice a very slight red glow if you look at the led`s on the camera). The camera picks up the infra-red light as it hits a surface and is reflected back, hence it can see in dark !


I/R cut filter
This is a mechanical device which slides an infra-red filter in front of the camera lens during the day to improve colour rendition. At night when the camera switches to black and white and the infra-red led`s turn on the filter slides away. We don`t generally favour I/R cut filters as they have a habit of failing either through age or environmental extremes (freezing conditions mainly).


DSP
Digital signal processing. This is the general term used to describe improvement of the initial image. It also incorporates additional features such as backlight compensation, motion detection and so on. This takes place on microchips separate from the CCD or CMOS sensor. Also referred to as the Chip set.


Dual CCD cameras
This is a solution sometimes used for cameras with built in Infra-red lighting. During the day the colour CCD is used to record images. When light levels fall the Infra-red led`s turn on and the camera switches to a separate black and white CCD. This allows a high definition black and white CCD to be used. Whilst in theory you have the best of both worlds in practice you have twice the complexity and also twice the amount of setting up to do.


IP rating
This refers to how resilient the camera is to dust penetration and water penetration. It is quoted as a double digit number. The first number relates to dust protection and ranges from 0 to 6 with 0 offering no protection, 6 offering total protection. The second number refers to the level of water protection and ranges from 0, no protection, to 8, total protection from long periods under water under pressure. The numbers that interest us are 5 – protection against low pressure jets of water sprayed from all directions, 6 – protection against strong jets of water, suitable for use on a ship`s deck, 7 – protection against temporary immersion up to 1m for periods of up to 30 minutes. In practice anything over IP65 is suitable for outside use. If you live in a lighthouse then you might want to up the ante to IP66 or even IP 67.


NTSC, PAL & Secam
For reasons best known to someone else there is no worldwide standard method of broadcasting television images. North America, half of South America and most of Asia use a format known as NTSC. We in the UK along with most of Europe, Australia, East Africa and parts of Asia use a system known as PAL. There is a third  broadcasting system called SECAM used in France, Eastern Europe and Western Africa. Normally SECAM televisions will also accept PAL signals but don`t bet your life on it!

If purchasing equipment make absolutely sure it is compatible with your television system. NTSC and PAL do not work together.  All our products are sold as PAL versions so you will have no problems in the UK

 

There`s a lot of information in this CCTV camera buyers guide and to be honest we`ve taken care of most of it for you in our choice of which cameras we chose to carry in stock. Decide what you want your CCTV system to do, choose a camera body type that suits your needs then select a lens combination that will work best in that application. If in doubt go for a zoom lens and you`ve got all the bases covered.

 
We also have a CCTV DVR advice section and a CCTV accessory advice section which you might find helpful.