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Cameras - how well can they address multiple purposes?

Faced with the costs of installing a CCTV system, people often try and reduce expenditure through compromising and trying to get cameras to address multiple needs at once.

Poor identification of people may be traded off for a general view of the area by a fixed camera that allows monitoring of general activities. This may also take the form of camera sharing by multiple users. For example, between the security and the production department of a site who both require camera views for different purposes. Another problem scenario is when operators from different control rooms attempt to change camera views to their own specific purpose and ruin the required view for the other party.

Defining the operational requirements for a camera usually requires clear specification of the purpose of the camera, what is to be viewed, and the criteria for effective viewing. Where the camera is to be used for multiple purposes, a formal agreement between the different camera 'clients' needs to be established to regulate such use. If a specific purpose is not defined for a camera and this is not adhered to, it all too frequently results in the camera not doing anything properly and everybody being unhappy.

Pan, tilt, zoom

The use of a PTZ for multiple roles must result in limitations for at least one purpose - by its nature, the PTZ involves active use to be effective. In viewing one situation, the operator moves the camera view to a specific location and has to compromise viewing of another. While PTZs have the advantage of being able to track people and objects, and zoom in close to observe and identify issues, this same capacity then blinds them to what is going on in the wider scene.

This has led to the comment that perhaps PTZs should be complemented by fixed cameras that provide a consistent recording of the site, while the PTZs are used to track or obtain close images of targets or situations.

Certainly, as part of best practice, the PTZ should be parked after close viewing use so as to address general viewing requirements. This should be done either through an auto park feature or a manual placement of the PTZ after use.

Identification crisis

The most frequent casualty of this poor definition of camera purpose is the identification of suspects, which must take place with small inadequate images of faces in a scene characterised by a broad view of an area. Various statements over the past few years, including by at least one UK police force, have indicated that 80% of video material provided for evidence has not been fit for the purpose.

More recently, this was acknowledged in a Home Office publication on CCTV, which states 'anecdotal evidence suggests that over 80% of the CCTV footage supplied to the police is far from ideal, especially if it is being used for primary identification or identities are unknown and identification is being sought'.

Similarly, a sizeable proportion of the video that I encounter leaves much to be desired, and the use of digital systems has possibly made the problem worse rather than better. What would have been an appropriate camera view is subject to a high compression ratio to fit onto the storage facility.

The consequence is that in replaying the video the pixilation has made people, objects, or behaviours extremely difficult to identify effectively. Even camera views that would have been suitable are rendered unusable after recording because of the loss of image quality due to compression. In worst cases this has resulted in the video being withheld from being used as evidence because the quality is simply too poor to make valid conclusions from. The use of remote surveillance also becomes susceptible to this with compression making views displayed to the operator somewhat different to what the camera is initially providing. To evaluate camera suitability in remote surveillance situations, one therefore has to check what the quality of visual image is at the remote site where a response decision is being made, rather than what the camera is capable of producing locally.

The costs implications of choosing camera types and numbers go way beyond the initial purchase price. The number of cameras impacts on the capacity and cost of the system that is ordered, and has long-term implications for maintenance and replacement costs down the road. Further, the use of PTZs to replace a number of fixed cameras also needs to be done with caution. A PTZ needs to be implemented for a specific purpose and cannot be expected to do the job of multiple fixed cameras at the same time. Ultimately we may find that the inappropriate use or coverage of cameras is having a far greater effect than use of lower quality cameras or lenses. It may well be best to have fewer cameras doing a good job than many which are providing an inferior picture that is not fit for purpose.

Dr Craig Donald

Dr Craig Donald is a human factors specialist in security and CCTV. He is a director of Leaderware, which provides instruments for the selection of CCTV operators, X-ray screeners and other security personnel in major operations around the world. He also runs CCTV Surveillance Skills and Body Language, and Advanced Surveillance Body Language courses for CCTV operators, supervisors and managers internationally, and consults on CCTV management. He can be contacted on +27 (0)11 787 7811 or [email protected]

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