BOOT CAMP 025
& PICTURES PART 1, SCANNERS
Getting photographs into a PC used to be incredibly
difficult. As recently as five years ago it was almost impossible, without
access to eye-wateringly expensive peripherals. It's also worth remembering
that the PCs of the early 1990s (mostly 386 and 486 machines with 8Mb of memory
or less), were only barely capable of displaying and processing high quality
colour pictures. That's all changed, today's Pentium PCs are cheaper, faster
and vastly better equipped to handle photographic images. Competent colour
scanners now sell for less than £100 and digital still cameras are not far
behind -- we'll be looking at them in more detail in part 2.
This week however, is devoted to colour scanners, and why
your life is incomplete without one. A scanner is arguably the most versatile
computer peripheral yet devised. It will enable you to load high quality
photographs and images into your PC, for incorporation into documents, presentations,
newsletters and Internet web pages. Most models also come with a suite of
utility software that can turn your computer into a sophisticated photo studio,
colour photocopier, fax machine and document reader.
First generation scanners were cumbersome to install and use
but most recent ones, including many current budget models, can be up and
running in a matter of minutes. There are basically two types of
general-purpose scanner, utilising two sorts of PC connection. Most
non-specialist models are either flatbed or sheet-feed; a few hand-held models
are still available but they're virtually obsolete now. A flatbed scanner looks like a small
photocopier. The image or document is placed face down on a glass plate or
'platen' and scanned by a moving image sensor, on the other side of the glass.
On a sheet feed scanner the image sensor is static, the document moves past it,
drawn though a set of rollers, rather like a fax machine. Flatbeds can take up
a lot of desk space but they are able to scan unwieldy objects like books or
irregularly shaped items. Sheet feed scanners are usually a lot smaller or
incorporated into multi-function devices like combined printers and fax
machines, but they can only cope with a single sheet of paper.
Scanners either come with their own interface card or they
connect to the PC's printer port. The former means you will have to open up
your PC, and it must have a vacant card slot on the motherboard for the SCSI
card (see jargon filter). They tend to be more expensive too but they're also
slightly quicker, however, scan speed is largely irrelevant. Unless you're
planning to regularly process large number of images saving a few seconds is
hardly important. Parallel port scanners are suitable for 95% of home and
office applications, the only minor limitation is that you cannot scan and
print at the same time, though the printer remains connected to the PC, via a
'through port', on the back of the scanner.
Scanner resolution creates a lot of confusion. Resolution is
a measure of how much fine detail the scanner can capture. The only figure that
counts is optical resolution, which is typically quoted as a set of two
numbers, i.e. 300 x 600 or 600 x 1200 dots per inch (dpi). The first figure
indicates how many light sensitive elements or pixels there are on the scanner
pickup head, that traverses the image or document. The second number shows how
many vertical 'lines' can be scanned by the pickup head, as it steps along the
picture or document.
The important point to bear in mind is that most
applications -- where the scanned image will be shown on a PC monitor screen,
or printed out by an inkjet printer -- calls for a resolution of between 100
and 200dpi. Good quality colour photographs may go up to 300dpi, but only a
handful of professional applications need 600 dpi or above. A lot of budget
scanners claim to be able to resolve 2400, 4800 dpi, or more, but that is an
'interpolated' figure, which basically means the software guesses at what's in
between the actual scanned dots. A lot of the time it gets it wrong and
interpolated scans can look soft or slightly blurry. Another point to bear in
mind is that higher resolution scans take longer, use up more hard disc space
and memory to store and manipulate the image. A 4 x 6-inch colour photograph
scanned at 2400 dpi would swallow up several hundred megabytes of memory!
A scanner is heavily dependent on its operating software.
All models require a driver program, the most common one is TWAIN (see jargon
filter), it operates in the background, usually from within the scanner's user
interface. This is normally features a preview window -- showing a small
thumbnail version of the scanned image -- plus a set of control buttons. The
driver automatically adjusts brightness, colour and contrast (manual controls
are usually there if you need them), all you have to do is select the
resolution and the task (i.e. picture acquisition, copier, fax, document reader
etc.). Incidentally, Windows 95 comes with a simple scanning utility. It's
called Imaging and can be found in the Accessories folder on the Programs menu.
Most scanner operating programs have the facility to make a
fast preview scan, to check orientation and alignment etc., before the full
scan. When it has finished the image is automatically routed to the appropriate
application. For example, if it's a photograph the picture will appear in an
open window on the desktop of the selected graphics program. If it's a fax, the
scanned document opens your fax software and a document to be converted into
text first passes through an optical character recognition (OCR) utility where
it is converted into a text file, which can be read by your PC's word
processor. Most scanners come bundled with graphics and OCR programs, though
more often than not they're 'lite' versions with a limited range of features.
Before you rush out and buy a scanner there's a couple of
points to bear in mind. Scanners work best with fast Pentium PCs and Windows 95
-- the faster the better! If you're using an old 486, forget it, no matter what
it says on the scanner box. Scanners also need lots of memory and hard disc
space, reckon on at least 32 megabytes of RAM, (64Mb is better still…) and
several hundred spare megabytes on the hard drive.
Next week -- digital cameras in the frame
Optical character recognition -- software that
translates a scanned image of printed or typewritten text into a plain text
file that can be read by a word processor
Small systems computer interface or 'scuzzy', a high-speed
data interface that uses a card, which plugs into an ISA (integrated system
architecture) socket on the PC motherboard. SCSI cards that use PCI (peripheral
component interconnect) slots are also available
Technology Without An Important Name, an industry-standard
software utility that operates in the background, acquiring an image from a
scanner or digital camera
If you're spending several hours each day staring at your
computer's monitor screen it's important to make sure it is properly set-up.
Incorrect picture settings can result in fatigue, headaches and eyestrain.
Adjusting brightness and contrast by eye can be quite difficult. Monitors also
go out of alignment, but some picture faults-such as slowly deteriorating
focus, geometry or colour registration is difficult to spot in their early
stages. For that reason it's worth periodically checking your monitor with a
program such as Ntest. It was created by Nokia's monitor division and features
a dozen test patterns, to help you set up your monitor and give it a complete
health check. What's more it's free! You can download NTest from the Nokia web
site; it is a 1.2Mb zip file, so you will need a decompression utility like
WinZip to open it up.