Technical information

ICT in the science department 1618 © CLEAPSS 2005
Some cameras produce quite small images that cannot be enlarged. With some
software, it can be difficult to find where captured images have been saved on the
computer by default. While programs generally offer facilities to adjust settings, it
might not be easy to work out how to do this. There can be problems of incompat-
ibility between the camera software and existing software or hardware on the
computer. Some software cannot cope easily with networked computers, making it
less suitable for use in schools with no stand-alone computers.
While most companies are happy to assist with such difficulties, vast amounts of
time may need to be available for setting up and familiarisation with the soft-
ware. Equipment needs to be checked before the lesson to ensure that it is
working as expected.
Resolution, frame rate and other factors
When viewing images captured by a camera on separate display equipment, there are
important factors to consider which may affect the quality of what is observed.
Resolution specifications for cameras
Camera specifications might quote either separate figures for the vertical and horiz-
ontal resolution or the total resolution, as in Table 16.5.
Table 16.5 Camera resolution data
Vertical × horizontal resolutions (pixels) Total resolution
512 × 382 = 220 Kilopixels
640 × 480 = 310 Kilopixels
659 × 494 = 330 Kilopixels
768 × 586 = 450 Kilopixels
1240 × 1024 = 1.3 Megapixels
Typical resolutions for flexcam-type cameras are currently 300-400 kilopixels (eg, 640
× 480 pixels); web cams have similar specifications. This is similar to the low-resolu-
tion setting on standard computer monitors. Images from such cameras will be
adequate when viewed on a computer monitor. However, still and video cameras
typically have higher specifications, which are usually quoted as a total resolution
value: 2-3 Megapixels would give suitable images for more-detailed school work.
Resolution specifications for displays
The ultimate limit of resolution is determined by the number of effective pixels on the
camera chip. For an object viewed by the camera, details that are smaller than one
pixel cannot be detected; light from them contributes to the overall information rec-
orded by the single pixel on which it falls. Modern display technology does not,
however, always match capture technology.
Camera and
display resolution
When the camera and display have similar resolutions, each pixel of image will be
displayed by one pixel of display. This ideal matching is often not the case.
Display with
inferior resolution
If an image is displayed on a device of lower resolution than that of the camera,
information from a block of ‘image’ pixels must be shared on a single pixel of the
display. Less detail will be detectable. The information is, however, still present
and is available for use in other applications or with displays that have a higher
resolution.
Display with sup-
erior resolution
If the number of vertical pixels for the display [usually the second number quoted
in specifications (eg, ‘480’ for a ‘640 × 480’ display but sometimes given as the
number of lines)] is greater than that for the camera, the displayed image will be
smaller in size and will not fill the screen. This typically occurs when using cam-
eras of resolution 640 × 480 pixels and screens with a resolution of 1024 × 768.
This problem is most noticeable with software that displays an image in a small
window, within the screen, that cannot be expanded.