Watch the positioning: The VDP20 dome from deView

01 Nov 08

What our experts say …

Things have come to a pretty pass when CCTV camera manufacturers have to insert the word 'True' in front of a feature, but we can see why DeView felt it necessary. The market is currently awash with cameras purporting to have 'day and night' capabilities.

Through widespread misuse it has become a virtually meaningless piece of marketing guff, like 'hi-fi' and 'digital' and, although there is no officially sanctioned definition, once upon a time it used to mean something.

In our view, for a camera to qualify for day/night status it needs three things: very low light capability. Below 1 lux seems like a fair breakpoint. It should be able to automatically change from colour to monochrome operation when light levels fall below a preset threshold, and it should have a mechanically switchable infrared filter in front of the lens, to optimise image quality in black and white picture mode.

The deView VDP20 dome camera ticks all three boxes and earns extra Brownie points for being vandal-proof and weather resistant with an IP66 rating thrown in for good measure.

It is a compact design with a 4-inch transparent dome and designed for indoor and outdoor operation, in a surface or flush mounted configuration. The camera module is based around 1/3-inch Sony interline CCD with a 752 x 582 pixel array.

Colour/day sensitivity is an impressive 0.65lux, dropping to a more modest 0.25lux in monochrome/night mode. Resolution is a claimed 540/570 lines in day and night modes respectively.

The camera can be fitted with a range of lenses; our test sample came with a 2.9 - 10mmF.12 type with DC auto-iris. Exposure options and controls are limited to switchable auto white balance, internal or line-locked sync, flickerless mode, backlight compensation, AGC, sharpness and day/night switching threshold.

The BNC terminated video output and power cable emerge though the top of the case. It requires a 12VDC or 24VAC supply and comes with an unusually extensive fixing kit that includes screws, wall plugs and a tamper-proof Torx key for removing the dome cover.

The case is made from a tough polycarbonate, indeed, virtually everything inside and out is made from plastic. This is no bad thing, and at cursory glance it all seems very well put together. However, we noticed something that could turn out to be a bit of a problem.

The camera module is mounted in a simple gimbal arrangement, basically a ring within a ring, giving it three axis of movement (pan, tilt and rotate). The outer ring attaches to the inside of the housing with three screws, and this is where things could start to go wrong. When the camera module is de-mounted, to fit the power and video cables, it can very easily be put back into the wrong position.

There's no keying or visible markings that we could see, and the instructions are ambiguous, so there's a 1 in 3 change of getting it wrong, at which point the edge of the ring presses down on two small daughter boards, mounted on the inside of the case (one is for the power supply, the other is an interface board).

The contact with the latter PCB shouldn't cause any problems but on the other board the ring presses hard against an electrolytic capacitor and regulator diode, stressing both components and their soldered joints creating a potential failure point.

It really is no more than careless design and very simple for the manufacturer to fix, but it shouldn't have happened and spoils an otherwise well constructed piece of kit.

Setup and operation

Camera alignment poses no problems, there's no need to slacken off any locking screws as the three-way mount uses ratcheted friction bearings. Once the camera has been set it should stay in position and nothing short of violent physical shock is likely to make it move again – we will see how good it is when it meets the Security Installer rubber mallet later on...

The controls, such as they are, all live on the camera module and are accessed by removing the camera liner (a simple push-fit). They comprise an 8-way DIP switch and two rotary presets, for setting DC iris level and vertical phase. From top to bottom they are TDN (True Day/Night) on/off, AWB normal/extended, Sync internal/external, Flickerless mode off/on, BLC off/on, AGC normal/turbo (the latter for cameras operating in predominantly low-light conditions), Sharpness normal/on, and D&N low and high (threshold presets).

This should make setup a reasonably quick and simple affair, the only problem is the switches are deeply recessed and tucked down beside the lens barrel. In short they're a pig to get at, especially if the camera is mounted high or at an awkward angle. To make matters worse getting at the switches involves blocking the lens, so you can't see what effect any change of setting has until your hand is out of the way and the AE system settles down.

Performance

In ideal conditions, in good natural light the image is a little soft and struggling to get anywhere near the claimed resolution figures. There's a noticeable improvement when the sharpness control is switched on, though the extra processing means that straight edges can appear jagged and there is some patterning.

Since the manual exposure adjustments are so limited, and there's no scope for external control the on-board automatic controls need to be very effective to be able to operate in the range of conditions this camera is designed for. The best we can say is that auto exposure control is adequate. Bright lights and windows in the scene can cause problems and no amount of fiddling with the BLC and AGC switches makes any difference so the only recourse is to realign the camera to avoid the problem. In more straightforward situations it copes fairly well and the automatic white balance system manages to produce reasonably accurate looking colours in artificial, natural and mixed light.

In low light conditions it works well with relatively little noise, until it levels get close to the sensor's limits. The changeover point from colour to monochrome mode is about right, though seems to take a little longer to switch back to colour, when light levels increase.

We are pleased to report that the camera never flinched during its session with the SI rubber mallet, nor did it have any effect on the alignment of the camera so apart from the previously mentioned concerns, build quality and construction both appear to be very good indeed.

One final point, which may or may not have implications for long-term reliability, is how hot the camera module gets. We expect electronic modules to run a little warm but the metal screening can around the module actually gets hot to the touch. It's not quite enough to cook an egg but heat means wasted energy and when electronic devices get hot their life expectancies are shortened.

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