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Of course it’s probably just a bizarre coincidence but when removed from its housing the Pelco Spectra III dome camera module looks uncannily like a small policeman’s helmet!  Unfortunately the ‘helmet’ is hidden from view inside its protective casing so any deterrent effect is lost but maybe there’s an idea here for an enterprising manufacturer…


The Spectra III SE sits at the top of Pelco’s range of small multi-role dome camera systems. It is available with three camera configurations (colour/black and white, colour and monochrome) and a very wide range of housings to suit just about any application, from prestige office or retail interiors to harsh outdoor environments. We’ve been looking at the high-end DD53CBX-X colour/B&W camera/drive unit and a standard weatherproof Pendant housing.


Before we get down to the nuts and bolts we’ll begin with the customary guided tour of the main features of the dome unit, starting with the business end. The camera module is based around a 1/4-inch CCD with a 724 x 582 progressively scanned pixel array giving a claimed resolution of 470-lines. It’s mounted behind a F1.6 lens (f 3.6 – 82.8) with a 23x optical zoom (& 10x electronic zoom). The lens provides a 2.5 to 54 degree horizontal angle of view (tele to wide) with an end-to-end zoom speed of 4.2 seconds. Low light sensitivity is down to just 0.013 lux in black and white mode with slow-speed (1/15th sec) shutter enabled, or 0.3 lux at a standard 1/50th sec. Colour low light sensitivity is 0.08 lux at 1/15th sec. All focus, exposure and white balance systems are fully automatic, with manual overrides via a menu-driven on-screen display system; we’ll look at what that entails in a moment.


The camera is mounted on a motorised turntable with continuous 360-degree rotation; pan speed is manually variable between 0.1 and 80 degrees/sec, up to 150 deg/sec in turbo mode and up to 360 deg/sec under preset control. The camera tilts through 90 degrees at between 0.1 and 40 deg/sec under manual control and up to 200 deg/sec when accessing a preset.


The password protected on-screen displays can be accessed from any one of a number of compatible Pelco controllers. In addition to pan/tilt, zoom, focus and exposure functions the controller also configures things like shutter speed, AGC and picture sharpness functions. Other exposure facilities include a Wide Dynamic Range (WDR) mode, which optimises image quality in scenes with extremes of light and dark by adjusting brightness, contrast and shutter speed settings. The picture auto flips when tracking a subject or object passing beneath the camera and pan and tilt speeds are automatically adjusted according to zoom magnification. The camera can be programmed to move to any one of 80 preset positions and each position can be assigned up to four motion detection areas, which may be positioned anywhere in the screen area and adjusted for sensitivity.


One rather unusual feature on this model is Window Blanking, which allows the user or system administrator to define up to 8 four-sided areas to cover up windows or parts of the image to prevent them from being viewed. Two types of Window Blanking are available, ‘gray’ or ‘smear’; the latter is semi-transparent, so that movement but not details or features can be distinguished. The Window blanking feature can also be reversed, so that only the defined area is visible but the rest of the picture is blanked out.


Camera movement programming facilities include four user-defined ‘Patterns’ made up of sequences of pan, tilt, zoom and preset position actions. The camera’s field of view can be divided up into 8 definable zones, each of which can be enabled or blanked. The dome has 7 alarm inputs with programmable priority (high, medium, low), and user defined actions, which include going to a preset position, running a pattern or switching to auto scan or random scan modes.


One of the most noticeable features of the dome module is the light and deceptively simple construction. The chassis and mechanism is made almost entirely of a tough high density plastic, not a metal casting in sight. This results in a very low mass and doubtless contributes to the unusually high rotational speeds and accurate positioning, but more on that later. The camera unit is small and self-contained with just a single ribbon cable connecting it to the rest of the unit. It’s built inside a simple open metal case and mounted -- via a large (plastic cased) ball-race to the side pillar. Tilt action is driven by a simple toothed pulley connected to a chunky stepper motor. The mechanism is mounted on a spoked wheel-like turntable; once again plastic is used throughout. The turntable is connected to a second stepper motor, again by a toothed drive belt.


Above the turntable is the electronics compartment, which contains two PCBs, responsible for motor control, communications, video processing and various housekeeping functions, such as power supply and regulation (it requires an 18 to 30 VAC supply) and cooling, courtesy of a tiny thermostatically controlled fan. A huge amount of electronics has been crammed into a small space but the layout is clean and uncluttered and wiring to the outside world has been greatly simplified using just two multi-pin connectors, which mate with a pair of connectors mounted in the top of the pendant housing. Additionally there’s also an RJ45 socket on the outside of the unit -- accessible when the dome unit is installed in its housing -- this is used for diagnostic and servicing purposes such as updating the camera’s operating software. 


The dome unit snaps quickly and easily into position inside the housing and is released by pressing two protruding levers, helpfully labelled ‘A’ and ‘B’, to assist alignment. A safety strap fitted to the inside of the housing prevents the camera unit from an accidental tumble. Access to the connections panel is very good indeed, even with the pendant fixed into position. The camera connectors inside the housing are mounted on a metal plate that drops open to reveal a set of set of detachable plugs for the alarm inputs and outputs and comms signals. The power supply connections are on a separate screw terminal and the video output is handled by a flying coaxial lead, terminated in a BNC socket and covered by a protective sleeve. All of the wiring feeds neatly through the mounting hole in the top of the pendant housing.  A ducted fan inside the housing assembly blows hot or cold area onto the inside surface of the transparent dome and presumably also helps to keep dust and dead flies out of the picture. Unusually the actual dome is made from a non-rigid plastic – it has a very similar feel to the ‘Pet’ (polyethylene terephthalate) material used to make lemonade bottles -- that should be able to withstand heavy and sustained attention from vandals without cracking or fracturing.



When used with a compatible Pelco controller the dome’s setup menus are enabled with a simple key sequence. The opening page has the operating language selection and three main menus: System Information, Display Setup and Dome Settings. Additionally this page also has three troubleshooting options, to reset the camera settings to factory default, reset the camera without changing settings and reboot the whole system.


System Information is for reference only and shows details of the dome’s hardware and software and comms settings (version numbers, configuration etc.). The Display Setup menu is concerned with managing on-screen graphics, including the position and duration of Preset and Zone ‘labels’, zoom ratio and position (azimuth and elevation). The Dome Settings menu leads to a number of sub menus. The first is Camera and this displays settings for lighting type (indoor or outdoor), auto focus (on /off), zoom limit (default 184x), low light limit (maximum duration slow shutter), IR cut filter (disabled when in B&W mode) and auto IR level, which determines the level at which the IR filter switches in and out. This sub-menu has an advanced Options screen with a variety of settings for manually setting shutter speed, AGC mode, gain, auto iris, sharpness, white balance, backlight compensation, video level and Wide Dynamic Range.


The Motion Settings sub menu handles dome movement parameters such as proportional pan, park time and action, limit stops, scan speed, preset freeze frame (the image freezes when going to a preset) and azimuth zero setting, so the camera’s position display can be aligned to compass settings. The Power Up sub menu sets camera action when the power is disrupted or cycled, options include resume prior activity, auto/random scan or pattern. Further sub menus are used to set synchronisation in multi-camera systems, program position Presets, Patterns and Zones, Windows Blanking, Motion Detection, Alarm setup and password setting. 


Menu layout is generally intuitive and easy to use, options are chosen using the joystick and selected with the Iris Open button. The dome instruction manual is a model of clarity, profusely illustrated with diagrams and screen shots and as a bonus, written in plain English… 



Camera performance is outstanding, particularly in low light situations and resolution is within a whisker of the manufacturer’s spec. In good light with the camera on the factory defaults it manages to produce a crisp image containing plenty of fine detail and texture, even in shadows and darker areas of the picture. Colour accuracy in natural and mixed light is normally very good in fact the camera’s auto systems can be safely left in charge in all but the most unfavourable conditions and when they run out of puff there’s a comprehensive set of manual controls to fall back upon.


The pan/tilt mechanism is amazingly agile and puts on an impressive turn of speed when moving between presets. The lightweight construction undoubtedly helps neutralise overshoot and at the other end of the scale movement can be very finely controlled, for tracking very slow-moving or distant objects at high zoom settings. 


Whilst the plastic construction has major benefits as far as camera movement is concerned there could be a question mark over mechanical stability and rigidity. In fact this proves to be groundless. The use of lighter and marginally more flexible materials does mean that the camera and dome assembly is slightly more susceptible to vibration and mechanical shock, compared with a traditional dome camera with a heavier metal or cast alloy chassis – a gentle tap to the case results in camera shake -- but in practice this is unlikely to be a problem, provided the camera is installed correctly and according to the manufacturers instructions. 



The evolution of dome camera technology has some interesting parallels with the development of the video recorder. In both cases first generation models were heavy and clunky, technically and mechanically unsophisticated and heavily reliant on a large number of metal parts, with plenty to go wrong or wear out. Nowadays the deck mechanisms in VCRs are mostly made of plastic, they’re very reliable and incorporate many more advanced features. The Spectra III SE mechanics are a very far cry indeed from early dome cameras, some of which looked as though they were built to withstand nuclear attack and earthquakes. The use of plastics has enabled Pelco to develop a compact, lighter, faster and more responsive mechanism, add to that advanced image sensors and optics, smart video processing and micro computer control systems and you’ve got a highly potent package. Only time will tell if it is hardier and more reliable but the signs are good, performance is excellent and anything that makes the installer and end user’s lives easier is to be welcomed.



Design and design features                      *****

Circuitry and components                *****

Ease of installation and wiring            *****

Range and variety of functions            ****

Accompanying instructions              *****                        

Technical advice and backup            ****    

Value for money                         ??                          



ã R. Maybury 2002 0407




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