CCTV camera buyers guide
Correct camera choice is critical to a good CCTV system. Many of the specifications traditionally used to compare different cameras are totally wrong. In this buyers guide we are going to discuss some of the key things to consider when choosing which one is right for your application and we are going to help you avoid common mistakes.
TVL or television lines - if you`re only going to read one thing then make it this !
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 you use a camera with the right lens for your particular application. No amount of TVL will allow detail to be captured beyond the limitations of the lens. Wide angle equals poor detail capture as you move away from the camera.
At D1 resolution your DVR records at around 400,000 pixels per frame. You need the lens to concentrate enough of those pixels onto the subject in order to capture detail. If a 450TVL camera allows you to read a number plate at 8 metres then a 700 TVL camera with the same lens wouldn't be able to read it at any greater distance.
Notwithstanding the fact that TVL isn't a measure of how much detail a camera captures the numbers used are often very misleading. We see instances where the black and white night time resolution is quoted, not the day time colour resolution or simply a made up number.
Choose the right lens
If increasing the TVL doesn't improve detail capture what does ? The answer is how much you zoom in on the subject. Most people think they want a wide angle camera to give the widest coverage. This is the single biggest mistake you can make and yet remarkably most of the cameras for sale in places like Maplins or other national retailers are wide angle.
As you move away from a wide angle camera the pixels spread apart rapidly and you only fill a very small section of the screen. As a guide at D1 resolution someone needs to fill 70% of the screen hight to be identified, 50% to be recognised.
In the images below we have a lower resolution camera on the left, a higher resolution camera on the right. Both upper images are the same angle of view. The increased resolution (higher TVL) doesn't improve detail capture. With the bottom images we have zoomed the lower resolution camera in more. This means even though is has fewer TVL it captures increased detail.
| Lower resolution camera
Bottom image is zoomed in more
|Higher resolution camera
Bottom image is wider angle
Zoom or varifocal CCTV camera lens
The best bet is to use cameras with a zoom or vari-focal lens. You`ll pay a slight premium over fixed lens cameras, around £20-£30 depending on the exact lens but it means you have much more flexibility. During installation you can zoom in or out to fill the image frame with your chosen subject and make best use of the available pixels. You can balance detail captured with area covered.
Digital and optical zoom, there is a huge difference
It is important to distinguish between digital and optical zoom. Digital zoom merely zooms in on the individual pixels until the image becomes unrecognisable.
With optical zoom the lens itself is doing the work before the image gets captured on the cameras electronic sensor. This means there is no pixelation, you increase the amount of detail.
We have optically and digitally zoomed in on the emblem of the antique car. As you can clearly see digital zoom produces no extra detail whereas with optical zoom there is a huge increase in the amount of detail.
| Optical zoom
| Digital zoom
Infra red or IR range
Do not confuse the quoted IR range of a camera with its optical range. Widely used in marketing the IR range is a pretty much made up number supposed to give an indication of how far from the camera you can detect it's built in IR illumination. There is no relationship whatsoever between the IR "range" and the distance at which detail can be captured. Most supposed "25 - 35 metre" cameras have an optical range closer to 5 metres, in some cases not even that. It really is a joke.
When discussing the effective range or "optical" range of a camera we refer to the distance at which a number plate can be identified during the day with the camera fully zoomed in.
Pro and Diamond Sony electronic Packs - our choice of electronics
The vast majority of our cameras are made for us to our own specifications. We work with our camera manufacturer and test different electronic components to constantly keep on top of available technology. There are lots of factors to consider not just the theoretical resolution. Simply choosing to use electronics from a manufacturer such as Sony isn't good enough, we need to look at individual CCD and DSP combinations within their ranges to come up with the best all round package. The photos below show a test we ran comparing 2 different high resolution solutions from Sony. Both are good quality high resolution combinations and the infra red light is the same in both images. As you can see there are significant differences in low light performance even within a Sony range
Results vary greatly even within high resolution electronics from a leading brand such as Sony.
We offer most cameras with 2 electronics options :
Pro spec electronics pack
A good quality high resolution combination of CCD image sensor and DSP chip set. Where this package really scores is in its low light capability down to as little as 0.01 lux. For most applications this package will be more than adequate.
Diamond spec electronics pack
Daytime colour rendition is slightly improved whilst still allowing the camera to function well in low light conditions. At night the image is processed more to give a better overall view. This processing does mean some ghosting can occur on moving images. Our diamond electronics pack allows some settings changes to be made on the camera. In most instances the camera is best left in automatic mode but for some specialist applications this ability may prove useful.
Local stores like Maplins and on line retailers such as ebay and Tesco sell cheap CCTV packages. Is there a catch ?
Quite a lot of places sell CCTV these days and you`ll often hear us putting down "one box solutions" sold by retail giants and on line. It`s all well and good for us to claim our products are better, but what does "better" mean.
Probably the biggest difference is that we take time to ensure the equipment you buy is suitable for your intended use. You can talk to skilled people on the telephone for advice and we carry a cohesive range of products, many of which are built to our own specifications, to ensure we have the right tools for the job.
The claims made by most people selling CCTV are simply laughable. We made a video to highlight the discrepancy between what the advertising blurb says and what the you actually get using a Swann Pro-535 camera, typical of the type sold by Maplins, Costco, Screwfix, electrical wholesalers and any number of on-line retailers. When our MD said he would happily stand naked 25 metres away from their "25 metre" camera we took him at his word.
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.
Just because a camera claims to have a Sony 1/3 inch CCD sensor doesn't make it a good camera. You need to know exactly what electronics have been used and then ensure it has the most suitable lens for your application.
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.
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 provenance of all components within our cameras. We do this by selecting manufacturing partners very carefully. It helps greatly that we travel overseas and have regular direct contact 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 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 as you move away from the camera. A 3.6mm lens won't be able to capture detail more than 4-5 metres from the camera. So when you see 3.6mm cameras which claim ranges of 15 - 20 metres this is pure fantasy. A longer, more telephoto lens can show increased detail over a narrower angle of view. This is the single most important thing to get right when choosing cameras. don't be afraid to call us for advice.
Different types of CCTV cameras
Infra-red (I/R) day / night 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.
A traditional looking CCTV camera. Good visual deterrent easy to fit and adjust with versatile mounts. All our cameras feature sturdy metal brackets which can be locked in place. They are often referred to as day - night cameras because of their ability to film in total darkness as well as normal daytime conditions.
CCTV Dome cameras
The camera electronics are housed behind a clear plastic dome providing protection and also making it harder to see exactly where the camera is pointing. Fitting and adjusting these cameras can be a little tricky and when infra red light is installed it tends not to be as efficient due to internal reflection from the clear dome.
Internal dome cameras without infra red tend to be in plastic housings, more hardy vandal dome cameras are housed in metal bodies for added protection against attack. Fitting Vandal dome cameras on extended mounts reduces their resistance to tampering because it is much easier to knock them off the mounting surface compared to when they are close fitted.
A recent development is the open dome
type camera which doesn`t have a half round plastic cover over the camera unit. Instead the camera is housed and protected in a tough round outer shell. Our open domes are constructed in metal and extremely sturdy. They are much easier to fit and install than a traditional covered vandal dome camera and the infra red is much more effective. an open faced vandal dome camera still affords good protection against tampering.
Finally there are speed dome or PTZ (pan tilt zoom) cameras which have electronic motors controlling movement in all directions. It is tempting to see PTZ cameras as the ideal solution because they can easily be re-positioned but unless you have a full time operator they can be an expensive folly. When pointing in one direction they are not filming in another and when moving they tend not to give good images due to blurring. We would suggest fitting more fixed cameras for the same price.
We sometimes get asked about tracking cameras designed to automatically track people as they walk about. Forget it, keep it simple and fit more fixed cameras for the same price. Ignoring the expense of the technology as soon as you have more than one person being tracked and they split up the technology fails.
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. These don't really suit themselves for general purpose CCTV work around houses, offices or commercial sites. Better to use an infra red equipped camera. Our bullet cameras are 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. You are however limited by a fixed lens and sometimes a smaller lens which lets limited amounts of light in.
Box or Body cameras
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.
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.
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.
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.
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.
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).
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.
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.