Turret cameras are not ideal for use in wide open spaces with significant depth of field.

I see more and more turret-type CCTV cameras installed in large public spaces and around major buildings. Am I missing something or do such cameras now offer serious surveillance capability for such applications?

A: This sort of camera is being selected for low cost. There’s no doubt some turrets offer a good balance of weather and vandal resistance, as well as being useful surveillance tools if installed with sympathy for their specification.

For instance, some users may choose longer fixed focal length turrets to suit their required view or they may install turrets to cover compact spaces. However, in most cases those who make decisions will be more interested in cost cutting than respecting the laws of physics – the cameras will have the standard issue 100-plus degree angle of view to go with their modest 1080p resolutions.

This combination of comparatively low resolution and wide angle of view gives turrets a focal sweet spot from a hyperfocal distance of say, 300mm, to about 6 metres from the lens. Much outside this range and they won’t deliver identifiable faces, though you will get situational awareness and clothing details.

It’s worth pointing out that there are 5MP and 8MP turrets appearing on the market. Cameras with more pixels on the same old 1/3-inch sensors will offer superior depth of field and greater detail during the day but they’ll give poorer performance at night in colour and monochrome, to the point pedestrians can’t be identified well enough to make footage court admissible.

It should please privacy advocates that just as face recognition technology reaches a state of frightening capability, very few users are prepared to pay for cameras capable of identifying faces in public spaces – especially moving faces, especially at night.