Where the cameras are being located and exactly what they are going to view.

Camera Purpose. This is a legal requirement for people or organisations installing CCTV.  Under the Data Protection Act and the Surveillance Camera Code of Practice you are not allowed to install a camera unless there is an ‘identified, pressing need’.  This should be justified at the design stage of the system.

Camera ID Level. Unless this has been calculated you have no guarantee that you will be able to recognise persons within the picture.  The wording of this standard should correspond to the ID standards within British Standard BS IEC 62676 – 4. This indicates that you will need a minimum resolution of 125 pixels per meter if you are to obtain Facial Recognition of a Known Person and 250 pixels per metre to obtain Facial Identification of an Unknown Person.


Pictures per Second. Normally the police require a minimum of 6 pictures per second but with the price of HDD storage reducing it is becoming increasingly common to record in true time (25 PPS)

This gives an indication of the lowlight capability of the camera.  It is important if you are wishing to view areas at night.

It is essential to calculate which lens is required and the appropriate field of view. If you double the width of the picture you will half the resolution obtained.

This indicates the appearance of the camera the common styles being box, bullet and dome cameras.Is a camera with a Wide Dynamic Range necessary? Using a camera without a Wide Dynamic Range when viewing doorways or windows from the inside will result in silhouetting.

Control Equipment

Size of hard drive. You will need to carefully consider the recording capacity necessary? With IP CCTV systems you can easily be looking at 1TB or more per camera for a month’s recording. This will also depend on how many megapixels each camera can produce. E.g. a 4K camera will require around 8 times the storage of a 1 megapixel camera

It is important to calculate the bandwidth which will be necessary to facilitate all your cameras? Often the usable bandwidth is only 60% of that which is available.  If you have insufficient bandwidth then the cameras will record at either a lower resolution or less pictures per second than is available.

Has sufficient thought being given to the convenience and security of your recording system.  NVR’s may well create a noise problem and this should be carefully considered.

Pictures per Second. This needs to be carefully calculated based on the pictures per second produced by each camera. 25 PPS will require over 4 times the storage of 6 PPS.

Record Resolution. A five-megapixel camera can be set to record at a fraction of its resolution.  Is it clear that you will get the full picture quality from each camera?

Download Writer. Best practice precludes downloading images to a USB stick.  WORM (Write Once Read Many) media, correctly packaged, can prove that images have not been tampered with.  If you wish to have resilient evidence in a court of law a CD/DVD writer is strongly recommended.

Does the quality of the monitor match the quality of the pictures produced by the cameras?

Is a secure cabinet required to ensure that other people, who do not need to, are prevented from viewing the images?  This is a requirement under the Data Protection Act.

Please do not assume that the above list is exhaustive.  There are other issues that can cause a system to fail the ‘fit for purpose’ test but I have tried to cover the issues that most often arise.  In offering this advice, The CCTV Advisory Service cannot be held responsible should other issues which may cause your system to be less than satisfactory.

The Association of Chief Police Officers have stated that 80% of cameras are not fit for purpose.  Often this is nothing to do with the quality of the camera but the lack of a professional specification and design, resulting in the wrong equipment being installed.  Unfortunately, most companies selling CCTV are not security companies (although they may have that label on their letterhead) but sales organisations.  The latter are primarily interested in simply selling a load of equipment and walking away with the money.

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