Scanner
Buying Guide
For picture
perfection, get the best scanner for the job.
Overview
Sensor Types
Scanning Area
Colour Depth
Grey Levels
Resolution
Interface
Transparancies and Slides
Speed
Application Software
Driver Software
Price Range
 Even
though the electronic-information age is upon us, we still live in a
world filled with paper documents. A scanner provides the essential
link between hard-copy information and your computer. With a
scanner, you can scan photos for Web sites or e-mails and translate
paper documents into word-processing files using optical character
recognition (OCR) software. Our guide will help you decide which
scanner is right for your needs
Overview
Which type of scanner you should choose depends on how you plan to
use it. Two popular types of scanners are photo and flatbed. As the
name implies, a photo scanner aids in digitising print photographs.
These handy units tend to be small--sometimes only six inches
wide--and are optimised for scanning colour photographs. They
usually offer quick setup and come with software to help organise
collections of photos.
Flatbed scanners make up the bulk of the general-purpose scanner
market. These models usually deliver the best combination of quality
and flexibility, and have only recently become available at
affordable prices. To use a flatbed, you typically place your
original under a flip-up cover; a moving scanner arm does the work
while the document stays put. If your scanning needs involve a mix
of photos, text documents and business graphics, a flatbed is the
way to go.
Sensor Types
Advancements in image-reading ability are rapidly changing the size
and complexity of flatbed scanners and forcing consumers to make a
choice between two technologies: CCD or CIS. CCD stands for
"charge-coupled device" and is the image-scanning chip that most
scanners have used until now. CIS (contact image sensor) technology
is a relatively new approach that simplifies the scanning process
and delivers smaller, lighter scanners. However, newer technology in
this case doesn't necessarily mean a better buy. While CIS is a
significant innovation, its scanning quality is still not quite up
to par with CCD.
Scanning Area
Scanners come in all shapes and sizes; when shopping for the right
model, make sure it has enough scanning area to accommodate your
needs. For example, you might ordinarily scan photos but
occasionally need to scan a full page of text. Scanning area usually
differs according to the type of scanner. The most affordable
flatbed scanners, for example, only handle originals up to 8.5 inch
x 11.7 inches, though some models can accept legal-size documents.
Photo scanners are a mixed bag in this regard as some have a more
limited width.
Colour Depth
The colour depth of a scanner determines the level of sensitivity it
has to various colours it reads from an original. This specification
is stated in bits, with common values ranging from 24 bits to 36
bits. Generally speaking, each bit represents a distinctive level of
brightness and sensitivity to colour. However, some manufacturers
implement colour depth differently, so a bigger number isn't
necessarily better. Though this rating is similar to the rating on
the number of colours your display driver or colour printer
provides, it isn't technically the same thing. In other words, don't
limit yourself to a 24-bit scanner because your ink-jet printer only
prints at 24 bits. While it may be hard to determine whether a
scanner makes the most of its colour depth, it's a good idea to
shoot for a model that offers at least 30 bits.
Grey Levels
Conceptually similar to colour depth, the number of grey levels
represents the sensitivity of a scanner to variations in
black-and-white originals. If you're scanning a black-and-white
photograph, for instance, the number of grey levels will determine
how well the digitised image will reproduce the subtleties of
shading. There is quite a range of grey levels among scanners, so
consider how important this feature is for your particular
applications. The standard is 256 levels of grey, although you can
find other models that offer over 4,000 shades.
Resolution
The resolution of a scanner determines how many distinct spots on
the original can actually be scanned--the higher the resolution, the
sharper the scanned image will be. This figure is expressed in dots
per inch and frequently varies between the horizontal and vertical
directions. There are two types of scanner-resolution ratings:
optical and interpolated. Optical resolution is the most important
figure to compare while shopping, as it indicates the hardware-level
resolution--the actual scanning density. Interpolated resolution
takes the results of the optical scanning and performs predictive
software techniques to create estimated dot values between those
that were actually scanned. While interpolation can improve the
quality of many documents, the optical resolution of a scanner
determines its true accuracy.
Look for an optical resolution of at least 600 x 600 dpi. Many
units feature 600 x-1200 dpi resolutions, which offer some
additional image improvement. If you're going to be scanning mostly
text and not photographs, you may want to opt for a 300 x 600 dpi
model to save money.
Interface
You can attach scanners to your computer in a number of ways. The
most common setup is to connect the scanner to your USB port. If
your computer doesn't support USB, look for scanner with an older
parallel-port connection. This interface often provides a
pass-through connector so you can keep your printer connected at the
same time. Scanners aimed at the professional market often use SCSI
to deliver better performance. These models usually come with their
own controller card so your system doesn't need a built-in SCSI
interface to accommodate the scanner. Choose the interface that
makes sense for the way you work--if you plan to move the scanner
between systems, a USB or parallel connection may be the best
option.
Transparancies
and Slides
The usual technique scanners use to digitise a page involves
measuring the light reflected off the original document. This works
fine for originals with opaque backgrounds, but transparencies and
slides require special consideration. For these, light must be
projected through the original and measured on the other side. Not
all scanners support transparent originals, and those that do often
require an optional transparency adapter. Bear in mind that you're
likely to need a flatbed scanner for transparencies.
Speed
Unfortunately, manufacturers' speed specification on scanners are
essentially useless for comparisons. Scan speeds run from seconds to
several minutes depending on the type of document you're scanning
and the resolution you're using. Manufacturers often quote speed in
the terminology that best serves their product. The interface a
scanner uses, however, makes a big difference when it comes to
speed--SCSI scanners are almost always faster than USB and parallel
versions.
Application
Software
Scanners usually come bundled with software matched to their target
market. Photo scanners, for instance, typically come with software
to save and manage scanned photographs. Because they are often used
by the entire family, they also have extremely easy-to-use
interfaces. Some bundles even include printing and Internet-related
software to help use scanned images to their fullest. Flatbed
scanners may come with additional software such as optical character
recognition (OCR) software to help create a "paperless" desktop (OCR
software converts a scanned image into a text document).
All scanners should come with basic image-editing software. While
scanners will work with other applications you may already have, it
pays to do a little research into the software bundled with a
scanner before you buy.
Driver Software
The driver software bundled with your scanner is a critical
component that will determine how easy scanning will be. Whether
you're scanning into the scanner manufacturer's own software or a
third-party package, the same driver interface will pop up.
Fortunately, a widely accepted driver standard called TWAIN ensures
your scanner will work with almost any scanner-ready application.
Most drivers offer a preview window--a picture of the scanning
area that lets you specify the region to be scanned and preview a
thumbnail version of the final image. This preview feature is often
used to automatically adjust the scan size to avoid useless white
space--and wasted time. Good drivers also offer plenty of adjustment
options, letting you set brightness, contrast, colour levels,
resolution, and colour depth.
Price Range
Scanners used to be an expensive add-on that only power users could
afford. Today scanners are available at virtually all price ranges.
Several units below £100 meet the needs of the casual home user
looking for functionality over performance, while many of those
costing between £300 and £400 are professional-quality models. While
more money won't always buy a better scanner, we suggest weighing
your criteria carefully and purchasing the most powerful and
flexible model your budget will allow--you're less likely to have to
upgrade in the near future.
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