|
Buying Guide--Scanners
by Amazon.com
How many times have you wished you had an electronic copy of that
special photo? How often have you had to laboriously type in an important
business document that only existed on paper? A scanner can help you bridge the
gap between the hard-copy and electronic worlds. Forget typing in documents by
hand; with optical character recognition software, your scanner can convert
hard-copy documents to text in the blink of an eye. You can also e-mail scanned
photos to friends and create professional-quality newsletters, calendars,
cards, and more. Scanners are now affordable enough for home users as well as
business professionals.
Overview
While the electronic-information age is approaching fast, 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 send outgoing faxes, scan photos for Web sites, and translate paper
documents into word-processing files using optical character recognition (OCR).
In today's all-digital world, a scanner is essential to a complete computing
system. Our guide will help you decide which scanner is right for your needs.
Scanner types
Which type of scanner you should choose depends on how you plan
to use it. Three popular types of scanners are photo, flatbed, and sheetfed. As
the name implies, a photo scanner aids in digitizing print photographs. These
handy units tend to be small--sometimes only six inches wide--and are optimized
for scanning color photographs. They usually offer quick setup and come with
software to help organize 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.
Sheetfed scanners are most often used for desktop
document-management tasks. Sometimes available in very compact and portable
cases, sheetfed scanners can automatically feed one or more pages. Sheetfed
scanners come in many styles, with some models offering functionality and
quality similar to photo scanners. Sheetfed scanners also frequently come with
document management software--to manage digital versions of your documents--as
well as outgoing fax drivers and optical character recognition (OCR)
applications. Many sheetfed scanners detach from their feeders to become hand
scanners that you can use to swipe book pages. If you're going to be mainly
scanning text, a sheetfed scanner can offer you more portability and a lower
price than a flatbed.
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.
CCD technology involves a precise arrangement of light source,
mirrors, lenses, and the CCD chip itself. The light is bounced off the original
document, directed through a lens, and focused on the CCD chip, which digitizes
the image. When calibrated properly, this approach works well--it's still used
in the vast majority of scanners on the market. However, its complexity adds
bulk and requires significant power to drive the light source.
CIS technology eliminates some of these hassles by combining a
series of closely placed LED light sources next to a row of tiny sensors.
Unlike a CCD configuration, which focuses an entire line of the scanned image
onto a small chip, the CIS models use sensors that run the width of the page.
The bottom line on CIS is that it allows for smaller and lighter scanners that
require less power--making portable models more feasible. While CIS is a
significant innovation, its scanning quality is still not quite up to par with
CCD. For now, it's a choice between image excellence and design convenience. As
CIS technology improves, however, look for it to compete head to head with CCD
in the quality arena.
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.
Sheetfed scanners, on the other hand, have a distinct advantage in that they
feed the paper through and therefore aren't so limited when it comes to paper
length (although the width is fixed). They usually handle at least legal-length
originals. Photo scanners are a mixed bag in this regard. While most feed the
originals like sheetfeds, some have more limited width.
Color depth
The color depth of a scanner determines the level of sensitivity
it has to various colors 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 color. However, some vendors implement color depth differently, so a bigger
number isn't necessarily better. Though this rating is similar to the rating on
the number of colors your display driver or color 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 color depth, it's a
good idea to shoot for a model that offers at least 30 bits.
Gray levels
Conceptually similar to color depth, the number of gray 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 gray levels will determine how well the digitized image will
reproduce the subtleties of shading. There is quite a range of gray levels
among scanners, so consider how important this feature is for your particular
applications. The standard is 256 levels of gray, although you can find other
models that offer over 4,000 shades if monochrome scanning is very important to
you--if you're going to do a lot of black-and-white desktop publishing with
photos, for example.
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. The
difference is a result of the technical limitations: one dimension is limited
by the accuracy of the optics and the sensor layout while the other dimension
is bounded by how precisely either the scanner arm or the original can be
moved.
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-by-600 dpi. Many
units feature 600-by-1,200 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-by-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 parallel port; this
interface often provides a pass-through connector so you can keep your printer
connected at the same time. Parallel-port connections are not the fastest but
are often the most convenient and universal. If your computer supports
universal serial bus (USB) connections, you can now find scanners with USB
interfaces. 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.
Paper handling
One of the important things to consider when buying a scanner
is whether you'll be scanning multiple-page documents. While many sheetfed
scanners can handle a modest number of pages at once, flatbed models generally
require an optional automatic document feeder (ADF) to feed multiple sheets.
ADFs can range in capacity from 10 pages to 100 pages and vary in price from
$100 to $500. If you're purchasing a sheetfed or photo scanner, consider how
many pages it can handle in its feeder; if you opt for a flatbed, check out the
ADF option--and its price.
Transparencies and slides
The usual technique scanners use to digitize 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'll likely need a flatbed scanner for transparencies; sheetfed models
generally do not support them.
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. Vendors 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.
Sheetfed scanners cater to a different audience, mainly business
users and home users looking for a way to fax documents from their computer.
Sheetfeds typically come with fax and copying utilities, as well as document
management and optical character recognition (OCR) software to help create a
"paperless" desktop (OCR software converts a scanned image into a text
document). Some sheetfed models include photo-management software as well.
Flatbed scanners frequently offer a mix of all these types of software, as
they're used for a wide range of photograph and text scanning.
All categories of scanners 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 vendor'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. TWAIN drivers vary in the complexity of their
interfaces and features, however--look for a driver that is easy to use, yet
offers enough flexibility for special tasks.
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, color levels, resolution, and color 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 $200 meet the needs of the casual home user looking for
functionality over performance, while many of those costing between $350 and
$400 are professional-quality models. If you're on a super-tight budget, there
are now flatbeds for less than $100 that will perform basic scanning tasks.
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'll be less likely to have to upgrade in the near
future.
| 