Two Eyes Better Than One

MEGAPIXEL cameras have a huge advantage. Their non-interlaced image streams deliver live video and still shots at such high quality that they allow genuine mining of scenes. In this context mining means digging deep into the field of view to extract the sorts of detail security managers long for. Things like numberplates in carparks and faces in crowds. Then there are the multifarious small incidents that take place outside primary target areas and that traditional cameras never adequately capture. What’s most interesting about Bosch’s foray into megapixel is the fact this company manufactures the current market-leading Dinion range of analog cameras. Taking this apparent attack on analog into account, what does megapixel mean to Bosch? Clearly it doesn’t underscore an expectation thatinstallers are going to turn away from analogue cameras and install megapixelIP gear wall-to-wall. Instead what’s going on here is that Bosch recognisesmegapixel cameras have a major role to play in topical applications wheremegapixel performance balances increases in cost, bandwidth and storage. There are 3 cameras in the Bosch megapixel range, with the flagship product being the NWC-0900, a dual sensor CMOS camera that incorporates a 3.1-megapixel half-inch colour sensor and a 2-megapixel half-inch monochrome sensor. With the NWC-900 the left hand camera and lens are for day mode and the right hand takes over at night. Automatic switching allows 24-hour performance in challenging lighting conditions. This is an IP camera and it’s designed to handle network environments thanks to PoE operation, selectable resolution and frame rate, and MPEG-4 compression that offers 32 images per second at up to 45Mbps – if that’sthe sort of super high quality you need. PoE is a neat feature that lets thecamera function anywhere there’s existing Cat-5/6 cable with no need to haul inmore copper. One of the beauties of PoE is the fact it allows surveillancecameras to hitch a ride on the network UPS in the event of power failure. Those adjustable resolutions are designed to help with slimming down transmission bandwidth but even the leanest is 1280 x 1024 (32ips) while the colour sensor delivers a gob-smacking 2048 x 1536 pixel at 15ips in applications where the highest possible quality is desirable. Essentially the NWC-900 Day/Night is 2 cameras in one, with separate sensors, lenses and iris settings giving the best possible performance during the day and at night. The configuration may be a bit hard for some techs to get their heads around but essentially Bosch is taking into account the performance variables associated with CMOS image sensors when compared to their couple charged cousins. CCDs offer greater sensitivity and introduce less noise when compared with CMOS sensors, while CMOS has better pixel frequency and does a better job with image cropping. At the same time CCDs experience vertical smearthat means manual iris lenses can only be used in internal applications. CMOSis fine with manual iris lenses but has geometry distortion with moving objectsat 45-degree angles. Taking all these elements into account, the best performance in megapixel configurations is a dual sensor day/night configuration where separate signal paths can be optimised for the best possible performance under given conditions. The last thing a CMOS-based camera needs is an IR cut filterfloating around between lens and sensor and with twin sensors and lenses, theissue is solved. Helping out with sensitivity is Bosch’s decision to go with ½-inch CMOS sensors. These are big chips and the extra surface area goes some way towards negating the reduced sensitivity of CMOS over CCD. “Megapixel is new for Bosch – we already have analogue cameras and IP streaming cameras,” says Bosch’s Sean Borg. “This new megapixel Day/Nightcamera is essentially 2 cameras in the one box and the depth of field and thedetail delivered means you can replace 4 or 5 analogue cameras in an application like a service station using a single megapixel camera and still get better performance than analog cameras would offer. “The megapixel decision very much depends on your application and I think you always need to keep the question in the back of your mind when thinking through an installation – when do I need a megapixel camera and when do I need a standard day/night? “I’m encouraging people to apply megapixel cameras to resolve specific problems in their installations. “Generally you’d use a megapixel camera in a surveillance system if you have the available link bandwidth, if you’re prepared for the cost of storage, or if really high resolution is vital during alarm events,” Borg explains. “Standard megapixel has single file sizes of 400k plus rather than 12 or 15k and that needs to be taken into account.” “There’s a general thought in the industry that megapixel cameras can’t be used in typical CCTV applications because the bandwidth they require is too high,” says Borg. “And while the bandwidth IS high, that doesn’t mean the overall solution can’t be designed in such a way that the great advantages of megapixel technology can’t significantly improve a site’s surveillance.“A particularly useful technique is to have megapixel cameras only record when the camera detects movement in a scene so as to ensure storage is not being pressured,” Borg explains. “The way the cameras are used really depends on the capabilities of the network and networks are improving. You wouldn’t build a network with less than gigabit switches these days.”According to Borg, megapixel cameras are unlikely to replace standard CCTV cameras any time soon. “It’s horses for courses,” Borg explains. “A site might need security at night in poor light and use traditional high quality CCD cameras to provide it. Meanwhile their internal cameras may be supported by good light so lower cost CCD cameras can be used. And several target areas might have significant depth of field and call for face or numberplate recognition – ideal applications for megapixel cameras.” “At the moment we have 3 products – the 900 day/night, the 700 is a 2 megapixel and the 800 is a standard 3.1 colour megapixel. The performance of these megapixel cameras is definitely superior to standard IP cameras and in the applications to which they are suited, megapixel cameras really are an awesome solution.” By John Adams, editor, Security Electronics & Networks Magazine