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DIRECT DTV 552 MONO CAMERA
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WHAT OUR EXPERTS SAY...
The proliferation of low-cost, miniature
board cameras over the past five years has created a thriving market for
concealed and covert video surveillance systems. Nevertheless, the primary role
of most conventional CCTV cameras is still to see, and be seen. However, board
camera technology and traditional video cameras are not necessarily unrelated,
as demonstrated by the Direct DTV 552 mono camera.
From the outside the DTV 552 looks like any
one of a dozen small surveillance cameras but appearances can be deceptive; the
extruded alloy case is pretty well empty! Inside there’s a small PCB on the
back panel, for DC power, auto iris and video output interconnections plus a
small switch, to enable the automatic shutter. Bolted to the inside of the
front panel there’s a single board camera module. In between there’s nothing
but two and a half inches of empty space, and a handful of connecting cables.
It is a little unfair to compare it too closely
with most standard board cameras. To begin with this one is slightly larger
than normal, moreover it has additional functions, and it uses high-grade Sony video
processing microchips and one of their 1/3-inch CCD image sensors. This has a 582
x 500 pixel array, giving a claimed resolution of 400 horizontal lines and a
low light sensitivity of 0.1 lux (f1.4). It has a relatively flexible exposure
system, with automatic gain control, the option of a automatic electronic
shutter (AES), auto iris lens (video drive only), or manual iris lenses. Once
engaged the shutter varies between 1/120th to 1/10,000th second. An auto iris
lens plug in to the back of the unit via a standard 4-pin square socket. The
manufacturers suggest leaving the shutter switched on when using an auto iris
lens as the two will work together in a complimentary fashion.
Despite the fairly anonymous exterior this
camera will surely attract a lot of attention, particularly from installers and
specifiers. Direct CCTV have bundled together the camera module, lens, mounting
bracket and power supply module for the impressively low price of just £99.
It is a very compact design, measuring just
59mm square, by 105.5 mm long. The all metal casing has two mounting bosses,
set into the top and bottom of the case. The all-up weight, including the
supplied lens is XX grams. The manual
iris ‘varifocal’ lens has a simple tele-wide adjustment with a focal length of
3.5 to 6mm and a horizontal angle of view from 74 to 44 degrees. This attaches
to the front of the camera using a standard CS mount; a C-mount adaptor ring
can also be supplied. An inner threaded sleeve on the mounting ring provides a
simple back-focus adjustment.
The standard of construction is generally very
good. The alloy case is tough and resilient, though a weatherproof housing will
be necessary if the camera is going to be to be used in a hostile environment,
or exposed to the elements. The camera module is populated almost entirely by
surface mount components (SMCs), which should make it extremely reliable, as
well as being tolerant to quite high levels of physical shock and vibration.
The only potential source of failure we could identify would be the internal wiring,
though the quality of the soldered joints on our sample was perfectly
satisfactory and gave no cause for concern.
OPERATION
Apart from the AES switch on the back panel,
and provision for an auto-iris lens, there are no further adjustments for installers or end users to worry
about. The supplied TA17 varifocal lens is a lightweight design, tipping the
scales at just 55 grams. There are three collars on the lens barrel; the
forward one for focus, the one in the middle is for the tele-wide setting. The
ring at the rear of the lens is knurled, this is used for setting the manual
iris. Minimum focal distance is 0.1 metres.
Installation and set-up should be quick and
simple in most locations. The supplied mounting bracket is a solid all-metal design
with a ball and socket head, giving a full range of movement. Video output is
handled by a standard BNC socket. Direct TV indicate that the maximum cable run
for the camera is approximately 100 metres, after which they recommend the use
of line amplifiers to restore the signal to it’s optimum level.
The plug-in DC supply mains module is rated
at 12 volts DC/350 ma, which is well within the 130mA maximum current
consumption of the camera.
PERFORMANCE
Resolution on our sample, in standard test
conditions with the supplied lens, was just a shade over 380-lines, providing
plenty of fine detail. Linearity is fine, the lens produces some very slight barrelling
on the wide-angle setting but the image is crisp and clean, with negligible
noise in good natural light. The AES is reasonably responsive, changing speed
smoothly. In reduced light levels there is a progressive increase in noise and
grain, though this only becomes intrusive in near-dark conditions. Automatic exposure
control is fairly average. Care has to be taken to avoid strongly backlit subjects
and it has difficulty compensating for any bright areas or lights within the
scene. Contrast is adequate, though again much depends on the care taken during
installation and set-up as the exposure system is not especially
discriminating.
OVERALL ASSESSMENT
Given the low price and relative simplicity
of the design it performs very well indeed and no compromises appear to have
been made in its construction. The DTV 552 is durable and if our sample is
anything to go by, it should provide years of trouble-free service. It is
perhaps better suited to undemanding situations, with only small changes in
light levels and scene illumination, however in such conditions our tests
suggest that it should function as well as cameras costing between two and
three times as much.
PRODUCT ASSESSMENT
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 *****
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Ó R.Maybury 1997 0504
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