Technical information

ICT in the science department 1616 © CLEAPSS 2005
be used at some point. In any case, sound can be added later with a separate
microphone. This can be sited appropriately, eg, near a person, rather than being
fixed to the camera where it might not be best placed to record the sound.
Power supplies
and safety
Web cams often obtain their power from the computer, via a USB cable. Cameras
with analogue outputs and digital models use low-voltage power from the mains
via a transformer or from electric cells. Connection to the display device will also
require leads. If these are not permanently connected in the laboratory and, if
more than one device is involved (eg, computer and monitor or VCR and TV
monitor), there is a proliferation of connections. Consideration needs to be given
to the safe positioning of these leads. See also section 16.5.9 (Projectors).
Safe mounting of
the camera
Some arrangements, especially with d-i-y adaptations and particularly when
microscopes are involved, can be cumbersome and precarious. It is important to
ensure that all equipment is stable and to avoid the risk that a heavy camera or
leads might pull over other items.
Security
Cameras are expensive, easily portable and desirable for everyday purposes. They
are difficult to secure while in use; when not under the direct supervision of staff,
they should be locked away.
16.6.3 Analogue or digital display?
Light and sound waves are analogue in nature. This means that colours, light intens-
ity, pitch and loudness can be continuously varied. Computers and other digital
devices use digital signals. These can only have discrete values (ie, they can vary only
in set steps). Each piece of analogue information needs to be converted to a digital
signal if the image or sound is to be processed by computers etc. The sophistication of
the digitising process is one of the factors that determines image quality in digital
cameras and microscopes. Digital signals will require further processing for use with
TV displays and other digital systems.
Some cameras and digital microscopes have only one type of output. In some cases, it
is possible to obtain an adaptor to enable the output to be displayed via a different
connection or format. See section 16.6.4 (Video connections and adaptors).
Table 16.4 overleaf summarises the equipment needed for different arrangements.
Important features of analogue and digital displays include the following.
Analogue (video)
display
If no permanent record of an image is required, connecting the camera to a tele-
vision or data projector will be sufficient and tends to be easier to set up. The
camera will require an analogue (eg, composite-video or S-video) output to do this.
S-video gives a slightly better-quality picture.
Images can be displayed on a screen via a video recorder/player. These displays
can be larger than those achievable via a computer. A video recorder can capture
images for future use but, unlike images captured by a DVD-recorder or comp-
uter, they cannot be directly manipulated. For some class use, this might not be a
consideration. If digital images are desired occasionally, these can be achieved if
the camera has a digital output or you have a suitable connector; see Table 16.6.
Digital display
and the camera
Some cameras are supplied with digital outputs. A camera or flexcam with only a
video analogue output can also be connected to a computer or other digital display
device (eg, data projector, interactive whiteboard) using a video-capture device
(refer to your IT department!). This can either be a PCI card installed in the
computer or provided by an external capture device (sometimes called, eg, a “USB
grabber”). A lead or leads with appropriate connectors and software are also
required; these would be provided with the external capture device or the digital
camera and possibly with some video-capture cards. Cameras which have a USB
or other digital type of output can be connected directly to a digital device without
the need to purchase a video-capture card. The image can be displayed via the
same equipment as for other digital material.