| Scanners provide a quick and simple method
of transferring images and text into your computer. They are invaluable
on a number of fronts - both in the office, where they have a number
of commercial applications, and at home, where they come into their
own for transferring photographs onto computer and e-mailing them
on to family and friends. Either way, they are an excellent organisational
tool, allowing you to sort and store your paperwork and photographs
electronically.
How do they work?
Scanners capture and convert images into a computer-compatible
format. They work in a similar way to photocopiers. A row of light-sensitive
sensors scan documents and translate the image into data that
can be understood by a computer.
Once stored on computer, this data can be viewed and/or manipulated
in a number of ways. Most scanners use Optical Character Recognition
(OCR) software which can identify printed text and drop it straight
into a word-processed document or attach it to an e-mail. Full
colour photographs and pictures can be scanned into a graphic
or photo-editing package and modified. More expensive scanners
have transparency adaptors which are used specifically for scanning
photographic negatives and slides - a good way of archiving old
photographs in digital format.
What to look for
Scanners capture and convert images into a computer-compatible
format. They work in a similar way to photocopiers. A row of light-sensitive
sensors scan documents and translate the image into data that
can be understood by a computer.
Once stored on computer, this data can be viewed and/or manipulated
in a number of ways. Most scanners use Optical Character Recognition
(OCR) software which can identify printed text and drop it straight
into a word-processed document or attach it to an e-mail. Full
colour photographs and pictures can be scanned into a graphic
or photo-editing package and modified. More expensive scanners
have transparency adaptors which are used specifically for scanning
photographic negatives and slides - a good way of archiving old
photographs in digital format.
Resolution
This refers to how many pixels a scanner can 'see' in any given
image. The higher the resolution, the sharper the image and vice
versa. Higher resolution scanners are more expensive but produce
a better end result. Generally speaking, a 2400 x 4800 dots per
inch (dpi) scanner should produce an acceptable level of resolution
for most on-screen images.
Bit depth
This is an indication of the level of detail and colour that can
be scanned. The higher the bit depth, the greater the number of
colours captured and the better the scanner is at distinguishing
between different shades of the same colour. The majority of scanners
are 48 bit, giving perfectly satisfactory quality.
Other features to consider
Interface
Different models of computer use different systems for plugging
in accessories. You should check whether your computer has a Universal
Serial Bus (USB), Parallel, Small Computer System Interface (SCSI,
pronounced 'scuzzy') or Firewire/IEEE 1394 Port and ensure your
scanner offers the same form of interface.
Computer memory
Make sure you have enough memory in your computer to temporarily
hold the scanned images. As a general rule of thumb, whatever
the size of the image file you are handling, you will need at
least twice the amount of memory to load it, preferably three
times. So if the image is 10MB in size you need at least 20MB
of memory. Remember that JPG and TIFF files can use up a lot of
memory.
Scanning area
Most scanners are designed to handle paper sizes up to A4 - an
area of 30cm x 21cm - but some are capable of handling the larger
A3 format - 42cm x 30cm.
Sensor types
There are three types of sensors used in scanners. Contact Image
Sensor (CIS) and Complementary Metal-Oxide Semiconductor (CMOS)
sensors are standard for home use - CMOS sensors being slightly
cheaper, CIS slightly better quality. Charged Coupling Device
(CCD) sensors offer professional quality and fast scanning, but
are more expensive.
Software
Most scanners come with a scanning utility program, which enables
basic handling of the image. They often also include an image
editor, for copying, enhancing, and modifying photographs; an
Optical Character Recognition (OCR) program for 'reading' scanned
text; basic desktop publishing programs; web tools for uploading
images to the web; a document management system; and, even, software
for designing your own greetings cards.
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