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HITACHI VK-C220E COLOUR VIDEO CAMERA
The Hitachi VK-C220 colour video camera is a
convincing demonstration of the growing importance of digital electronics, and
the impact that it now having in all areas of video processing. This camera
depends almost entirely on digital technology, from the CCD imaging chip and
signal processing circuitry, through to a specially designed RS232C PC
interface, which can be used by service engineers to access and adjust some of
the cameras critical functions, without taking the lid off.
This feature has migrated from domestic video
equipment, in particular camcorders, where, because of space limitations and
the need for a high level of reliability, methods have been devised to reduce
both the number of components and internal adjustments. To this end many
machines now have software set-up routines, with a growing number of key camera
adjustments stored as digital data on EPROMs (erasable programmable read-only
memories). Faulty or mis-aligned camcorders with this facility can be connected
to a computer running suitable diagnostic software, either locally at a service
agent, or remotely -- via a modem -- to
a computer at the manufacture’s main service centre. It is then a simple matter
to use the computer to identify errors and if necessary download corrected
data.
The VK-C220 doesn’t go quite that far, but
it’s clearly a taste of things to come. We’ll look at the PC interface in more
detail in a moment, but first a run through the general specification.
It’s a sub-compact design, the metal case is only
50 x 50 x 125mm, and it weighs in at just 370 grams (both measurements exclude
the lens). It is fitted with a C/CS lens mount, a simple screw-clamp adjustment
changes the mount from one type to the other. Behind the lens there’s a 1/3-inch
CCD image sensor with around 437,000 active pixels, that’s sufficient to give a
horizontal resolution of 460-lines; low light sensitivity is rated at 3 lux
(f1.4 lens).
The other headline features include a simple
to use menu-driven on-screen display (OSD) that givers the installer and
end-user ready access to a variety of additional functions, without having to
fumble with internal switches or buttons. They are: automatic or manual white
balance, variable shutter speed, from 1/50th to 1/10,000 th second, an 8-character
camera ident, backlight compensation, switchable AGC and ALC, neg/positive
switching and an electronic zoom with a magnification factor of 2x.
Within some of the selections there are
additional options. The camera ident is chosen from a full alphanumeric
character set and the finished title or ident can be superimposed on any one of
six locations along the top or bottom edges of the picture. The electronic
shutter has seven pre-set speeds (1/50, 1/100, 1/250, 1/500, 1/1000, 1/2000 and
1/10,000th sec), plus auto-exposure, where shutter speed is set automatically,
according to the incident light level. The automatic white balance function can
cope with most situations, though if the scene is lit by a mixture of differing
light sources manual intervention may be required. The OSD adjustment includes
an option to set white balance using a white reference card, or each colour can
be individually emphasised or demphasised as needed. The backlight control divides the image into six areas, which can be individually adjusted to correct
for strong backlighting. The areas to be masked are clearly shown by the
on-screen display.
All of the OSD functions are controlled form
a set of just three buttons, in fact they are the only exterior controls, apart
from the focus and manual iris adjustment (where applicable). On the back panel
there are four sockets, two BNC connectors (one for composite video out, the
other for external sync input), and two
mini DINs, for DC power and an auto-iris lens. Data for the RS232 camera-to-PC
interface and external switching (wide or tele) for the zoom facility are
routed via the power socket. There are standard threaded mounting bosses on the
top and bottom panels.
Internally there are five main PCB, all built
using surface-mounting component (SMC) technology, for improved reliability and
ruggedness, the boards are held in place by an all-metal chassis, it looks and
feels as though it’s built to last.
The PC interface or DAP (digital adjustment program)
is essentially a servicing procedure, rather than a user or installer facility
but it’s worth outlining how it works. The interconnection requires a small box
that fits between the camera and the computer; incidentally this has to be an
IBM or compatible machine, capable of running DOS software. The box has three connectors, one for the DC power
supply, the second one carries power and data to the camera, the other is a
standard RS232 serial interface that hooks up to one of the PC’s COM
ports. Once all of the connections have
been made, and everything switched on the program can be run by typing in a few
simple commands. This brings up a menu with two selections, for setting white
balance and chroma gain. The WB option gives access to red and blue colour
gain, which can be accurately set using
an oscilloscope or vectorscope. The adjustments are made from the
computer keyboard using a set of four defined keys. Once set the data is
written to the camera’s EPROM. The Chroma gain adjustment follows a similar
routine.
PERFORMANCE
The C220 meets all of Hitachi’s outline specs
with ease. Using a supplied Computar lens (12.5mm, f1.4) it produced a clean,
well defined image. In good natural light the autoexposure and white balance
systems can cope with a broad range of operating conditions but there’s
sufficient flexibility within the manual exposure options to ensure it can deal
with tricky situations. Noise levels are very low and although the low-light
performance isn’t going to break any records it still provides a useable image,
even in poorly lit scenes. The electronic zoom facility is a mixed blessing, on
the one hand it provides a quick and simple means of magnifying the image;
unfortunately at full power there is a drastic reduction in resolution with the
picture taking on a blocky appearance, with slight instability on fine, bright
detail.
OVERALL ASSESSMENT
In general performance terms the C220 is a competent
though unremarkable colour camera, however the range of advanced exposure
options, coupled with the small size and rugged construction combine to make
this an unusually versatile design, suitable for a wide variety of demanding applications. The efficient and
easy to use on-screen display, and the PC interface are key features that will
make the lives of installers and service engineers that little bit easier right
now, and hopefully, increasingly so in the future.
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 1995 3003
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