Looking to specify dome cameras to safeguard your company’s premises? If you are, then think of the whole process in parallel with what you’d need to bear in mind if buying the next family car. It really is as simple as that.
Having the right amount of power – and putting that power to effective use – is the key to performance under the bonnet of a car, and within a CCTV dome camera. Internal and smaller dome camera systems are usually fitted with compact chassis cameras. Large, external domes will support much bigger and heavier camera/lens combinations. A rather clever component called a ‘slip ring’ allows both data and power to pass to and fro between the camera and the outside world, while offering free and continuous movement.
Indeed, ‘continuous rotation’ is the key phrase. We’re not just talking about travel through 360 degrees here. Like a moving automobile, a camera in motion will generate inertia. Careful braking will be required to bring that camera to a controlled stop. Suddenly, applying the brakes will not bring your car to a smooth stop on the white line. Neither will it accurately position a camera at a pre-set.
Make sure, then, that the dome control system you choose has the ability to bring your cameras to a graduated halt, thus avoiding the overshooting of any targets and/or over-stressing the gear box and drive mechanisms.
Internal and external fully-functional domes (of 5″ and 6″ diameter) are usually supplied to the installer/end user with compact chassis cameras ready-fitted. Larger domes of up to 20″ in diameter are the preferred choice of most designers of town and city centre CCTV schemes because they can carry conventional high specification cameras and lenses.
Quality-conscious dome manufacturers select the best available from the world market. The leading brands have feature-packed, powerful units that are amazingly compact. Camera manufacturers that have introduced domes in recent years obviously use their own. Specialist dome manufacturers have the advantage of selecting the best at the time from the open market. Monochrome, colour and colour/mono switching for day and night use – and low light colour – are your choices. A dedicated colour/mono switching camera is what’s needed for night-time viewing.
When more camera power is required, the technically superb and higher specification conventional camera/lens combinations are used. There are many fine cameras on the market courtesy of the industry’s leading manufacturers, as well as a great array of high quality and optically powerful lenses from which to choose.
As well as the camera and lens choice, thought must also be given to the control system. If possible, end users should select domes and controllers made by the same systems provider. However, there may well be pre-existing control equipment to consider. Electronic control signals referred to as ‘protocols’ are used to communicate between the controller and dome. Protocols may be integrated within the controller, the dome’s receiver or an external interface (or converter). Compatibility is not usually a problem.
Often, dome camera manufacturers will be informed of – or provided with – the customer’s own choice of camera, lens and even receiver circuitry, and can then proceed to build the complete unit to a particular end user’s selected specifications.
Ensuring a clear, all-round view
As is very much the case with your car windscreens, a clear view all around is vital for the dome cameras on your site. Curved windscreens and windows are carefully designed to provide the driver with the very best possible sight of the road. The design and build quality of a dome camera’s acrylic sphere must give the camera the best ‘aberration-free’ view possible. That said, 100% optical accuracy is not technically possible. Even opticians can only work with tolerances of .25 dioptres!
The manufacturing process required to form a quality acrylic sphere is both complex and exacting. Many manufacturers – in particular those at the low cost end of the market – struggle to produce a consistently good result. Defects such as rippling can occur if the process is imperfect or quality control lacking.
End users should bear in mind the option of specifying smoked and silvered acrylics (coatings that hide the camera position from view). The very best domes are also fitted with an inner mask, thus keeping those observed completely foxed. As you might imagine, there’s a slight reduction in light levels because of the reflective or absorptive qualities of these materials. External dome camera systems are normally specified with clear acrylics, as maximum light will be needed at night.
The positioning of the camera tilt mechanism inside the dome can also have a significant effect. Ensure that when the camera is in its horizontal position, the view is not cut off at the top, nor spoilt by distortions in the acrylic close to the rim.
Avoiding ‘blind spot’ syndrome
If you have a particularly important or high risk site, then it’s usually the case that a dome camera providing a totally uninterrupted 360-degree view will be needed. A weakness of some cameras – particularly the pan and tilt type – is the occurrence of a ‘blind’ area. The mounting post supporting the camera will obscure a surprisingly high percentage of the view (up to 30 degrees, in fact) depending on the post diameter. This loss of view would be quite unacceptable for applications designed to cover, say, the centre of a car park.
Thankfully, there’s one product out there that overcomes this problem, and in a very clever way. In practice, said dome would be fixed directly atop a standard CCTV tower, and is supported from below rather than by way of the usual top fixing.
Such a ‘beacon’-style design has great advantages. The camera inside is mounted slightly forward so that it may view its own support tower. With no tower or bracket adjacent to the dome, there’s no risk of compromising its truly 360-degree plus 90-degree field of view. Note that this is possible even with a camera/lens combination of up to 340 mm in length. A very clever solution to an often-overlooked weakness in dome surveillance systems.
Of course, the very best way to evaluate optical performance is to see the image quality for yourself. Manufacturers are always willing to demonstrate their products, either by bringing the ‘show’ to you or inviting system designers, installers and end users to their in-house demonstration facilities. Take advantage when they do. Ask to see the acrylic spheres in isolation. Hold an acrylic up to a window. Fix your gaze on the window frame, not the dome, and then move the acrylic around. This simple test can show up any defects. Take a test drive!
The electronics and software systems that drive a dome camera are very complex. It follows that they must be well-designed and written. Certain features are expected (and made regular use of) by operators in the CCTV Control Room. Those operators become very skilled at using dome cameras, and would soon be frustrated by systems made difficult to control thanks to weak software.
There are several handy functions that end users should look out for when specifying their dome cameras. These are the ‘U-turn’, ‘return home’, ‘back’ control, ‘auto park’ and ‘patrol’ functions. Let’s look at each of these…
The ‘U-turn’ function drives the camera through 180 degrees at full speed. This can be handy when following a subject along a pathway, or a vehicle along the length of a lane or driveway. The camera moves at speed to pick up the action as it passes beneath the camera position. Meantime, the ‘return home’ function sends the camera back to its pre-set home position. Useful when the security team has completed an investigation and the monitoring officer wants to return to more general rather than specific views.
The ‘back’ control function allows the end user to move to a programmed pre-set, and then return ‘back’ to the previous, manually-selected position. In this way, the operator is afforded an easy way of monitoring a given site using a mixture of pre-set and manually-selected positions.
The ‘auto park’ would certainly be handy for the motorist, and is also a useful surveillance feature for the end user. When in this mode, the dome camera will automatically return to pre-set one – usually a general view – after a pre-programmed idle period.
Last – but not least – whether automatic or manually-selected, the patrol function drives the camera through a tour of pre-sets.
Another important function to check for is the ability of the camera to respond quickly to an alarm input. Ensure that the camera speed is good, and that it will take an intelligent ‘shortest’ route to its pre-set.
At the end of the day, try not to be bamboozled by numerous buttons and lists of functions. Look out for the key controls that your staff will find both useful and effective.
Domes with all the trimmings
For the large and medium-sized external domes, specialist manufacturers can supply a choice of trims and bracketry in order to maintain the aesthetic integrity demanded by the locality.
Fittings that match popular luminaires (ie light fittings) are available. These can keep your camera system discreet – even covert. UK-based manufacturers may even provide you with bespoke paint jobs, matching dome and bracket colour to other street fittings.
It would be true to say that the right dome – designed with aesthetics as well as performance in mind – can look very smart, in particular in towns and cities offering an historic flavour. That’s something a ‘techno’ pan and tilt set-up could never hope to achieve.
These days, vehicle manufacturers are placing an increased importance on driver safety. Gone are the pretty but next-to-useless chrome bumpers, to be replaced by practical and effective designs made from durable materials. Protection is provided by impact protection systems elsewhere on the vehicle (side impact, for example). Once fitted, dome cameras are also at risk from damage impact. Accidental – but more often deliberate – attack has to be kept in mind. End users who put together a system specification that includes physical protection from the start can prevent costly repairs and avoid unwanted ‘downtime’.
Most dome camera fittings are quite rugged, but the element that may require impact protection is the acrylic dome itself. A stronger, impact-modified acrylic can be used to make the dome, and will provide a good measure of protection for normal risk situations.
Where the threat is particularly obvious, a more robust method may well be essential. The solution offered by most manufacturers is to add a metal fitting to fend off any unwanted attacks. These add-on devices vary greatly. Some are quite a light duty wire mesh formed around the dome. Such a ‘chicken wire’ approach seems more of a perfunctory measure. Defence against blows from brick and stick-wielding attackers demands something a good deal more substantial.
The solution has to be strong enough, and therefore constructed from decent gauge metal, but it mustn’t obscure the all-important view of the camera. Metal cages have been tried, but unfortunately they look dreadful and can be difficult to access for maintenance.
Innovative manufacturers have come up with a design that works well. Constructed in one piece, an all-steel array of ‘fins’ forms a snugly-fitting shield around the dome acrylic. The fins are very substantial, but are carefully proportioned so as not to cause an optical barrier. With the camera fully zoomed out (ie to its widest view), the fins are only just visible. A faint grey line is all that can be seen.
As the camera moves through its zoom range, zooming in, the effect becomes undetectable. A surprising optical effect that works well for the system.
All change for surveillance?
To resolve changing system requirements, some manufacturers have devised easy methods of moving or changing cameras around without the need for re-wiring. Cameras are fixed in position via a special base unit. Should a change need to be made, the camera is unlocked and simply disconnected. The preferred replacement is then fixed in its place.
This non-technical procedure takes only minutes and may be carried out without de-activating the system (this is often referred to as ‘hot swap’, to use the accepted jargon).
Pre-sets and other programmed information can be uploaded into the new camera using simple software. A facility such as this may keep a camera system matched to a site with no expensive engineer involvement.
There’ll be cost savings for sure but, more importantly, system effectiveness will be maintained at all times.
