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Small black and white cameras remain the mainstay of video security. Two new cameras from Sony, based around their Hyper HAD CCD image sensors, broaden the choice available to installers, seeking high-performance cameras  for demanding applications




A few years ago it looked as though differences in performance and cost between colour and monochrome video cameras were being eroded, to the point where black and white cameras would eventually become obsolete. That now seems unlikely to happen, at least in the foreseeable future; black and white camera technology has not stood still, far from it, in fact on-going improvements in low-light performance and resolution will keep them ahead of the game for some time to come.


Part of the reason must be that advances in solid-state image sensor technology usually begin with monochrome devices, and this is certainly true with Sony's Hyper HAD (hole accumulator diode) CCD, used on the SPT-M102 security camera. Hyper HAD CCDs were originally developed for broadcast cameras, which typically employ three monochrome CCDs to generate a colour image. The sensors are mounted on a dichroic prism, which spits the light into its red, green and blue component colours, so they can be processed seperately.


The imaging chip used in the SPR-M102, and its stablemate, the SPT-M108 is directely decended related to CCDs used in broadcast equipment, it has a 290,000 pixel array (500h x 582v ), giving the camera a horizontal resolution of  around 380 lines, and a low light sensitivity of just 0.1 lux (f/1.2). The principle differences between the two models are a built-in mains power supply on the M108, which also has a line-lock capability, when used with multi-camera systems. Power for the M102 is supplied by an external mains adaptor, the choice is left up to the installer, though Sony do have a choice of suitable AC power supplies in their range.


Both cameras are housed inside tough, extruded alloy casings measuring 50 x 53mm. The M102 is 125mm long, the mains power supply on the M108 adds a further 35mm to the length, taking it up to 160mm. Neither housing is water or dust-proof, though there's few holes through which moisture or dirt can penetrate and few additional precautions need be taken, unless the camera is to be mounted in a particularly hostile environment. A mounting plate with a standard quarter-inch UNC threaded collar screws to the top or bottom of the case. The cameras can be used with C or CS type lenses; a back-focus adjusting screw, accessible through a hole in the side, slides the CCD assembly back and forth, to suit different types of lenses. Other external adjustments include a switch to select CCD iris (electronic high-speed shutter) or auto-iris lens operation, plus presets for varying picture brightness and ALC control, for aligning auto-iris lenses. Additionally the M108 has a vertical phase adjustment, for setting AC line lock, to minimise picture disturbance when the camera is used with a switcher unit. In the CCD iris mode exposure is controlled automatically, using a combination of AGC (automatic gain control) and an electronic high-speed shutter which varies from 1/50th to 1/100,000th of a second.


The back panels are equally straightforward. The M102 has a BNC socket carrying the video output, a four-pin socket for an auto iris lens, and a pair of screw terminals, for the 12 volt DC supply. The M108 has the BNC and auto-iris sockets, plus mains lead and on/off switch. Neither camera is supplied with a lens, but they do come with a 4-pin cable plug, for auto-iris lenses.


Inside the video processing circuitry occupies two sparsely-populated printed circuit boards, these are mounted horizontally on a sturdy aluminium chassis. The use of surface mounted components (SMCs) ensures a low component count and high reliability. Compared with some small cameras these look reasonably approachable, so if they do go wrong most competent service engineers should have little trouble with fault-finding and repairs.


Installation and alignment shouldn't pose any problems for installers, the only point to watch out for is the centre of balance on the M108, which is shifted towards the rear of the camera, by the buil;t-in mains power supply. Having the mounting plate so far forward doesn't help either, so the mounting bracket needs to be very securely tightened otherwise the lens will drift upwards.




Low light sensitivity is most impressive, images taken under very poor conditions still contain plenty of useful detail. For example, using a supplied Computar lens (f/1.4), it was possible to read a car number plates at a distance of 20 metres, at night under normal street lighting. The automatic exposure system operates reasonably smoothly and it quickly acclimatises to sudden changes in lighting level; it also copes well with bright lights within the picture area. Vertical smearing, which is a characteristic of this type of image sensor, is evident, though in good light it's possible to minimise the effect by adjusting the manual or auto-iris, or re-aligning the camera, if there are any static lights in the shot. The CCD is largely immune to comet-tailing or image lag, even on a darkened scene.


Picture definition is very good, both of our samples were up to specification with horizontal resolution a shade below 400 lines. The image is crisp, with plenty of contrast and in bright natural light picture noise is virtually non-existant. As light levels fall there is a slow but progressive increase in noise and grain though it doesn't become noticeable until the scene is in almost complete darkness, it's certainly less intrusive than most similarly specified cameras. In twilight conditions the image on the screen still looks as though it's being shot in good daylight, often the only give-away is bright street and car lights.




As far as performance is concerned it's difficult to find anything to compain about. These cameras are small, unobtrusive and exceptionally well designed; time will tell, but our initial impression is that they are tough, dependable and built to last. The prices too will take some beating; Sony have set a new standard by which other small black and white cameras will have to be judged.



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