What our experts say…
Integrated day/night cameras have been the subject of intensive development over the past few years. Most surveillance camera manufacturers favour the single sensor approach, with one highly sensitive colour camera module configured to adapt to changes in lighting by switching to black and white operation when illumination levels fall below a preset threshold.
Further improvements in low light performance are usually achieved by digital signal processing and shifting an infrared filter from in front of the CCD image sensor – necessary for accurate colour rendition – when the camera switches to black and white mode.
This arrangement is undoubtedly the simplest approach and it has no significant impact on the size of the camera. It also works reasonably well but it does involve a number of compromises.
The most significant one is that a black and white image derived from a colour camera is not going to be as good as one from a dedicated low-light monochrome camera. The sensitivity of colour cameras are improving all the time but monochrome cameras still have the edge, particularly in near dark conditions and in particular when used in conjunction with infrared scene lighting.
Canadian-based Extreme CCTV has taken the alternative route and the ZX55 Integrated Day Night camera is the latest addition to its unique range of dual-sensor models. It uses a colour camera for normal daylight lighting conditions, and when light levels fall, a second monochrome camera takes over, assisted by an onboard infrared light source.
The most obvious drawback is size, and it will be clear from the photographs that the ZX55 is quite a lump – in fact it measures 130 x 135 x 210mm and tips the scales at a hefty 6.9kg. The actual cameras, which are mounted one above the other on the right side of the case, only account for around one third of the unit’s volume. The remaining two thirds are taken up by the infrared lighting system and a huge hollow finned heat sink, which accounts for the major portion of the body of the camera.
The trade-off with size does however mean both cameras and IR illuminator are a single entity, which greatly simplifies installation and wiring. Moreover there are no problems with matching the light source to the requirements of the camera and the area to be illuminated.
Extreme has also simplified the setup. In fact, preliminary adjustments and configuration have been kept to a minimum, and in a lot of instances the unit will be ready to use straight out of the box.
By current standards the camera is a fairly basic design with few, if any extras or ancillary functions. The colour camera is a high-res type using a 1/3-inch CCD capable of resolving up to 480 lines. The monochrome camera, also based on a 1/3-inch image sensor, is a medium resolution design (420 lines) and both cameras are fitted with 6-13mm Varifocal lenses. The colour camera lens incorporates an integrated autoiris and IR filtration. Minimum illumination, as you would expect, is 0 lux, day/night switching is controlled by a photocell mounted between the cameras.
Heat generated by the IR illuminator is largely responsible for the camera’s bulk. The actual light source is a flat panel containing an array of 224 LEDs, which according to the specs is powerful enough to illuminate an area up to 200 feet in front of the camera.
The panel is mounted directly on to the body, which allows cooling air to pass freely through ventilation slots in the middle of the camera case. Power consumption when the IR illuminator is on is in the order of 50 watts, but such is the heat sink’s efficiency that it can function in a very wide range of conditions, from -50 to +60 degrees C.
The weatherproof and vandal-resistant case is designed for harsh and demanding outdoor environments and it is well suited to remote monitoring. The unusual design and construction only becomes apparent when the side access panel is removed – this is attached to the camera body by a wire safety cable.
The two camera modules are mounted on a steel plate bolted directly to the cast alloy body. The varifocal lenses have adjustment rings for focus and ‘zoom’ and are easily accessible; the colour camera also has presets for ALC and iris level. Immediately behind the cameras is a single PCB and this has a preset for controlling the day/night switchover point.
A cavity at the rear of the body houses the camera power supplies. The connecting cable has just three conductors for the power feed (24 volts AC) and composite video output. The cable is very well protected and passes through the integral mounting bracket arm and emerges from the base plate. This bolts to a purpose-designed junction box that doubles up as a wall-mounting block.
Setup and operation
Positioning the camera is exceptionally easy and the mounting arm is joined to the wall bracket by simple ball and socket joint. This provides a wide range of movement and once in position it is locked in place using a supplied Allen Key.
Lens adjustments are provided to compensate for any differences in the camera’s field of view, but as previously mentioned the factory setup is pretty good and should require little or no further adjustment. Nevertheless the instruction booklet goes into considerable detail and includes a section on ALC adjustment for fine-tuning the auto iris settings. Similarly the photocell adjustment can be safely left on the default value but it’s a simple enough matter to change it using the internal preset.
Performance
Both cameras provide a clean crisp image, and the colour picture is particularly impressive, with lots of fine detail, comparatively little noise and bright, natural-looking colours. There is no additional exposure or white balance adjustments but the auto WB system has no problems with natural daylight, which is likely to be the main illumination source in most installations. The exposure system is fairly rudimentary but it is reasonably responsive and reacts to changes in light level with little or no fuss.
As light levels fall there is an increase in noise in the colour image, and if the scene is lit by sodium or fluorescent light colour fidelity does tend to suffer, with a greenish yellow colour caste, but this is only likely to occur at or close to the day/night switchover point so it is really not a problem.
When the monochrome camera takes over there is a momentary flicker in the picture, lasting only a fraction of a second. The lenses on our sample had been accurately aligned so there was virtually was no difference in the field of view. The black and white image is pin-sharp and also has very little picture noise.
Light levels are maintained by the IR illuminator, which comes on at the same time, so the auto exposure system has comparatively little work to do. Even so, it copes well with bright lights in the scene area.
Contrast balance is good and even at zero lux, when the IR illuminator is the only source of light; objects within the scene area appear sharp and detailed. The supplied 850nm LEDs produce a visible dull red glow; for installations where this would be a problem invisible 940nm LEDs are available on special order.
What the manufacturer says …
ZX55 is the most powerful product in Extreme CCTV’s Integrated Day Night (IDN) range. An excellent colour picture by day is complemented by 60+ metres of infrared surveillance in total darkness. ZX55 creates light, captures the light and controls the light to provide the ultimate solution for true 24/7 surveillance.
Integrated into a single housing, ZX55 combines the latest cameras, lens and LED infrared illumination technology for an easy to install, easy to service “plug and play” solution. The camera incorporates a revolutionary new (patent applied) cooling system that allows for power performance using only 50W.
ZX55 automatically switches between two cameras, utilising two separate CCD sensors. The first provides accurate daytime colour rendition, the second, a highly sensitive IR monochrome CCD, provides a high clarity night-time picture without focus shift or picture compromise. A high signal/low noise picture is assured with ZX55 and the use of long life, low energy, LED illumination makes for real savings in terms of running and maintenance costs.
The ZX55’s long life capabilities and 60+ m of day and night surveillance make it ideal for many applications including remote sites, perimeter surveillance, border control and many commercial installations.
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