The bench test 1: Clean image

What our experts say …

It’s not difficult to understand why fixed dome cameras have become so popular with installers and end users in recent years. Unlike a traditional fixed surveillance camera setup, with its attendant ironmongery and exposed cables, they are much more discreet and better able to blend in with contemporary decorative styles.

The fully enclosed design is easier to weatherproof, it provides a higher degree of vandal proofing, it’s more stable and the contained environment for the camera and its associated electronics should also help improve reliability. There’s also a significant deterrent effect. To the untrained eye there’s no way of telling if there’s a moving camera inside the dome, or where it is pointing. Small fixed dome cameras are often simpler to install and on a more mundane level they are easier to keep clean.

Of course there is the cost factor to bear in mind and the relative inflexibility when it comes to the choice of lens and general specification. Repair and maintenance can also be more difficult, but on balance the pluses far outweigh minuses and if you need further convincing then the subject of this Bench Test might help you to make up your mind.

The TK-C205VP is one of a family of fixed dome cameras from JVC, this model having a conventional analogue coaxial video feed; it is powered by a 12V DC or 24V AC supply. Other options now available or in the pipeline include twisted-pair video feed, more advanced optics and telemetry control and a choice of dome finishes.

JVC has sought to address the question of lens selection by equipping the C205 with versatile manually adjustable 2.6 to 6mm (F1.2 to F1.8) optics, which gives an angle of view of between 82 x 59 degrees at the ‘wide-angle’ setting, to 35 x 26 degrees in what amounts to a ‘zoom’ mode. The image sensor on our test sample is a 1/4-inch, 440k pixel interline CCD with a 752 x 582 array giving a resolution of around 535 lines. Minimum illumination is quoted at 1 lux.

Exposure is largely automatic with just a set of basic manual controls for adjusting iris level or sensitivity, AGC (on/off), Backlight compensation (on/off) auto/manual white balance and Spot Correction, which we’ll look at in more detail later on.

Tough lightweight alloy

The case is made from a tough lightweight alloy and it is in two parts with the camera, its pan/tilt mount and the electronics housed in the top cylindrical section. The lower part comprises the dome and shroud and is attached to the main body using three security bolts – a key is provided – and a drop-prevention cable. A rubber sealing ring between the dome and body keeps out moisture and dust and it is rated for both indoor and outdoor operation. Several fixing methods are possible; the body has standard pipe/conduit fittings on the base and side. Incidentally, JVC is to be congratulated for unusually clear and easy to follow instructions.

With the dome removed the camera and its pan/tilt mounting bracket are very easy to get to. The camera sits inside a simple U-bracket with a pair of locking screws at either side for setting and fixing the tilt angle (+80 to -50 degrees). Pan angle is adjusted by slackening off a single locking screw; this allows the camera mount to rotate through 350 degrees. Additionally the camera can be twisted in its mount to compensate for horizontal alignment. Image size and focus are set using two small twist-to-lock arms attached to the lens.

The plate on which the camera is mounted has a 6-way DIP switch. The first one opens the iris for setting focus. Switches two and three are for AGC and Backlight control. Switch number four sets auto or manual white balance and the remaining two are for internal or line-lock synchronisation and line-lock phase. Next to the switch are two recessed presets; these are used for setting both red/blue WB levels and line-lock phase. A pair of push buttons activates the Spot Correction function and white balance/phase reset. Moving further around the plate there is a phono/RCA socket carrying the video output for connection to a monitor. This is used when aligning the camera when the dome is in position and to the left of that is a preset for the Iris Level control. A three-pin socket next to the monitor phono is used for service/diagnostic connections.

Two captive screws hold the circular camera and electronics module in place in the upper housing. When it is released the module drops down, the connecting cables protected by a second suspension wire. The camera electronics are on a single PCB sandwiched between the two halves of the camera module, it’s very rigid and all of the components are well protected. A p.26 smaller PCB fixed to the base of the upper housing has screw terminals for the DC supply and video output. A small clip in the base holds a silica gel pack (included), to absorb any moisture that might find its way into the dome.

Set-up and operation

Electrical installation really couldn’t be any simpler, with just two connections to make for the power supply and video output. There’s plenty of room inside the case but care needs to be taken when the unit has been mounted, to avoid the electronic module and dome dangling on their suspension cables, coming into contact with one other and possibly scratching the camera lens or the surface of the dome.

Once the camera orientation and focus have been set they can be locked off and nothing short of an earthquake is likely to shift them. The expo-sure controls are also very straightforward and in most instances the auto systems can be relied upon to cope with normal variations in lighting level.

The white balance system is also capable of dealing with both natural and artificial light – and a mixture of both – though manual intervention may be necessary to tweak colour levels in locations lit predominantly by fluorescent light.

The Spot Correction facility mentioned earlier is a little unusual and the instruction manual talks vaguely about white spots appearing in the image when the dome operates in high temperatures. For the record, the camera’s recommended operating range is 0 degrees to +40 degrees C. Should any spots appear – and the system claims to be able to cope with up to 32 of them – the procedure is to cover the lens and press the Spot Correction button for more than two seconds, whereupon they should disappear. Short of popping the dome in an oven at gas mark 3 for a few minutes there’s really no easy way to test this feature so we’ll take it as read that it does what it says.

Images from dome cameras often suffer from annoying internal reflections, particularly when there is a strong light source nearby. However, the TK-C205VP seems to be largely immune and the image remains clean with a lot of fine detail, even when exposed to direct sunlight. This is even more impressive in view of the thickness of the dome.

The resolution on our sample was shown to be at or very close to the manufacturer’s specs and noise levels are very low. In good natural light colours are accurately rendered and the exposure system operates smoothly, efficiently tracking small and large changes in lighting level. Operation in low lighting levels is also impressive considering the minimum illumination is a fairly modest (by current standards) 1 lux. The image does get progressively grainy but it still looks a lot cleaner than many similarly specified models. The loss of detail and reduction is contrast is also less than many rival cameras with supposedly better low light characteristics.

Mechanical stability is excellent and both the camera mount and the video output were unaffected by a sound thrashing from the Bench Test rubber mallet.
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What the manufacturer says ...

Built with a cast alloy upper housing, the TK-C205VP fixed dome camera is very well engineered. Able to withstand any kind of shock, rain or extreme temperatures (-10 to +50 degrees C), the dome is so durable that a hard hit of a hammer would barely scratch it. These cameras are ready for anything.

JVC’s innovative digital signal processor automatically adjusts the camera’s parameters to ensure sharp and natural pictures with 535 TVL of horizontal resolution and high performance.

This unit is a simple plug and play dome camera with a vandal-resistant construction.