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General purpose colour surveillance cameras are by their nature a compromise but in any situation where lighting conditions can vary from pitch blackness to intense sunlight there is simply no alternative. What really separates the wheat from the chaff is a colour camera’s ability to handle very low lighting levels and this has proved an enduring challenge for designers, and spawned a number of ingenious, though not always successful solutions.


One answer is to amplify the signal coming from the image sensor chip and this can help increase the amount of information in the picture but at the expense of significantly raised noise levels, which degrades the image. A more successful technique is frame integration of ‘slow shutter’ but the trade-off here is a reduced image refresh rate and blurred movement. A third method is to switch to monochrome operation at a predetermined lighting level, though in order for this to work the Infra Red filter in front of the image sensor has to be dispensed with to increase the camera’s sensitivity. However, IR filters have a purpose and that is to ensure colour fidelity in normal light, though the effects of doing away with the filter can be reduced by the video processing circuitry.


The Samsung SDN-520 colour camera utilises the latter method, with a twist, which it calls ‘Day & Night’. In normal light it functions just like any other colour camera, with an IR filter in front of the image sensor but as soon as the light levels falls the filter automatically swings out of the way and the camera switches to monochrome operation. Incidentally, this system was pioneered on consumer camcorders, in particular models made by Sony featuring a ‘NightShot’ recording mode. This enables recordings in near dark and total dark conditions (using a built-in IR illuminator). It’s clearly no coincidence that the camera uses a Sony image sensor and, as an internal examination revealed, a fair number of Sony video processing chips.


The general specification puts the 520 into the busiest and most populous sector of the colour camera market. Two models are available, with slightly different low-light characteristics; the SDN-510P uses a 1/3-inch Sony CCD with low light sensitivities of 0.5 lux (F/1.2) for a colour image and 0.03 lux in monochrome operation. The SDN-520, which we’re looking at here, has a top of the line 1/3-inch Sony Ex-View Hyper Had CCD rated at 0.5 lux in colour and 0.01 lux for B&W operation. Both sensors have an operational 752 x 582 pixel array, yielding claimed resolutions of 480 lines (colour) and 520 lines (B&W).  


Key features, over and above ‘Day & Night’ operation include a simple motion detector facility, electronic shutter operating in manual or auto mode over a range of 1/50th to 1/10,000th sec, internal or external sync, backlight compensation, a positionable user-set on-screen ident of up to 14 characters and an RS-232 remote control facility. It can be used with video or DC controlled auto iris lenses and all functions are controlled from a simple to use set of on-screen displays. 


The all-metal case – without the lens -- measures 55 x 57 x 135mm. At the front, embedded in a tough alloy casting there’s a standard CS mount lens collar with a simple back-focus adjustment. A C-mount ring adaptor is included with the unit. There’s not much to see on the sides of the case, apart from a standard four-pin socket for an auto iris lens. On the back panel the familiar points of reference include a BNC socket for the composite video output and a pair of screw terminals for the 12-volt DC/24 volt AC power supply. Additionally there is a miniature slide switch for selecting auto iris mode, a small four-pin socket marked ‘Remote’, a green power on LED and a cluster of five buttons arranged in a standard cross-shaped ‘cursor’ formation.  


Removing the steel shells that form the case reveals a simple chassis design with the video processing and power supply circuitry plugged into a ‘motherboard’ fixed to a steel base plate, bolted between the cast alloy end caps. The tiny servo motor that moves the IR filter is mounted inside the front cap. Internal wiring is kept to a minimum and the whole assembly appears to be very rigid, it passed the SI rubber mallet test without missing a beat.



There are no nasty surprises for installers even the instructions are in English... A mounting plate with standard 1/4-inch threads bolts to the top or bottom of the case and a microscopic Allen key is included with the outfit for locking and unlocking the back-focus adjustment. The only point to watch out for when locating the camera is to allow for the video output plug and lead, which adds a good 20 to 30mm to the overall depth, so care should be taken when mounting it close to walls. The case is not very well protected against ingress of dust or moisture so appropriate measures need to be taken if it’s to be used in a hostile environment, 


Pressing the centre button on the cursor control brings up the main on-screen display menu page. Item one is for setting the camera ID and positioning it on the screen. Item two is the backlight compensation, it can be switched on and off and there’s a simple weighting adjustment which by default focuses control on the centre 20% of the screen area. The motion detector setup is next on the list, the size and position of the activity can be adjusted from the cursor buttons; the area of concern is shown on the screen as an opaque rectangle. There’s also a sensitivity adjustment for the motion detector, on a scale of 0 to 10. Item four is for selecting and adjusting the auto iris lens and item five is for manually setting the shutter speed. Menu six on is gain control, the options being off or AGC with manual adjustments for brightness and gain limit. White Balance is next, there are three modes: auto, auto tracing and manual. Menu item eight is the colour control and there are four selectable modes: On – colour operation only, Off – monochrome only, Auto 1 -- for daylight/fluorescent operation and Auto 2 – when the scene is mostly lit by incandescent light. Finally there are menu switches for selecting internal or external (line-lock) synchronisation and Reset, which returns the camera to its factory default condition. 



In good natural daylight picture quality is excellent with crisp natural colours, evenly balanced contrast, negligible amounts of picture noise and lots of fine detail, putting it within a whisker of the manufacturer’s claimed resolution figure and marking it out as one of the top performing cameras of its class. The auto exposure controls are fast and effective but a touch jerky and if you watch closely you may become aware of the brightness ‘stepping’ in response to changes in lighting level. Backlight compensation, in spite of being dubbed ‘Super BLC’ works reasonably well but doesn’t appear to be noticeably more effective than most of its rivals. The motion detector is a very useful extra with a good range of adjustment, to help eliminate false activation and it can be used to trigger and external alarm via the RS232 ‘Remote’ connection on the back of the unit.


So far so good but the real test lies in the camera’s low light abilities. The little motor that movies the IR filter, in response to a drop in lighting level is surprisingly noisy but it only takes a fraction of a second and picture disruption is negligible. The only minor quibble is that it would have been useful to have some control over point at which the changeover occurs. The change from colour to black and white brings about a marked increase in picture sharpness and a drop in noise, though this does start to creep up again as the light level drops further. At the point when most rival cameras are starting to give up the ghost the SDN-520 is still going strong, delivering a clear and highly detailed image and although there is a steady increase in noise the picture remains bright and stable with good contrast down to near dark conditions.



We are suitably impressed. The 520 is very well built and easy to configure but the real benefits are clear to see on the screen. It’s a true dual role camera with above average performance in normal light but it shows its worth in the sort of low conditions that even some specialist cameras have trouble with. 



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 3009



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