White Paper: Scanners link your PC to the real world


White Paper: Scanners link your PC to the real world

Prices of scanners have fallen dramatically, making them available to a wider audience. But which technology should you invest in?

The price for scanners has fallen dramatically. A few years ago, a 24-bit, true-colour flatbed scanner easily could have cost a cool £2,000. Today, you can find one for as little as £400. Under £1,000 scanners abound, many capable of scanning at ultra sharp resolutions that not long ago were out of reach of anyone but well-heeled graphics professionals. Almost all units come with capable image-editing and Optical Character Recognition (OCR) programs. Many can be equipped with optional sheet feeders and slide adaptors to speed up document processing and turn transparencies into digital images.

Scanner installation and operation are smoother nowadays, thanks to TWAIN drivers, which lets you scan material from within many Windows applications, and colour-management systems, which automatically adjust colours so that what you see on your monitor will match what comes out of your printer. Moreover, with Windows 95 and its Plug-and-Play specification, scanners should be even easier to get up and running in the near future.

Scan this, scan that

Though most scanners perform worthy double and triple duty ( scanning a page of text one moment, a piece of line art the next, a photo after that ( it's smart to start your decision process by deciding which task you'll perform most. That will keep you from spending money for functions you really won't need.

Scanner choices may seem complicated; some manufacturers offer a dozen or more models or configurations. Nevertheless, there are really only three variables to consider. First, do you want a handheld scanner, which you drag over an image manually, or a flatbed? Second, do you need a colour-capable scanner, generally a 24-bit device that can produce theoretically 16.7 million colours, or a greyscale unit limited to 256 shades of grey? And third, do you need high resolution capability of 600 dots per inch (dpi) or more, or will a 400 dpi or lower resolution scanner suffice?

For occasional scans of small pieces of paper or small portions of a page, a handheld scanner makes the most sense. Handheld scanners' most compelling quality is their affordability - 256 greyscale models are available for less than £70 direct, with colour units available for about twice that.

They come with utility software for stitching together multiple strips or passes over wide images; though stitching software often works surprisingly well, the process is too slow for any kind of volume. Moreover, handheld scanners are being crowded out of the market, in some instances, by a new crop of compact desktop models, equally handy for occasional digitising and superior OCR and document-processing work.

If you're recruiting a scanner primarily to import photos and other artwork for publishing purposes, you'll want a flatbed model. Don't overbuy, however. Match the scanner's resolution with that of your intended output device. If you'll be digitising photos for later printing on a 600 dpi monochrome laser, for instance, you'll be satisfied with a 600 dpi greyscale scanner. A higher resolution colour scanner makes sense for prepress colour separations or enlarging scanned images such as small photos or 35mm slides.

If text import via OCR software is your top concern, you need not worry about high resolution or colour. Shop for an affordable greyscale scanner that has a top notch OCR package bundled with it. That said, remember that while you may not need colour now, you may in the future. With colour printers' prices falling and resolution rising, the newsletter you print on a monochrome laser today may come out of a colour inkjet tomorrow. Since price differences between identical resolution greyscale and colour scanners are as low as £200, it can be smart to pay the extra amount now rather than buy a new colour scanner later.

One if by hand

Once the only choice for scanning on a budget, handheld scanners have been pushed into the bargain basement by the declining price of their full-page, flatbed cousins. Even so, they still fill a useful niche. Like their flatbed cousins, handhelds combine a light source with a charge coupled device (CCD) that reads the reflected light intensity and converts it to digital information. Rather than use a motor to move the scanning hardware past the image, a handheld scanner depends on your muscle power. That's a disadvantage, since few of us can drag a peripheral across a page as smoothly as a machine can.

Also, because handhelds scan such narrow three to four inch strips, you're either limited to small images or skinny columns of text, or you're at the mercy of the software used to stitch together multiple scans. Make sure a handheld scanner comes with stitching software before you buy. Ask, too, if the scanner/software combination can warn you when you're moving the scanner too quickly, causing it to skip part of the page or image.

On the positive side, handheld scanners are easy to install ( most plug into a PC's parallel port, making it easy to move the scanner from one system to another or to carry one with a laptop PC. You'll find greyscale and colour capable handheld scanners with resolutions as high as 400 dpi. It's difficult, however, to perform accurate hand scans at resolutions above 200 dpi, since the higher the device's resolution, the slower and steadier your hand dragged path must be across the image.

The mainstream choice: flatbeds

The advantage of flatbed scanning is clear as soon as you start scanning even a short stack of documents or images. Slap down the paper, close the lid, click on your software's Scan icon or press a key, and the CCD moves down the length of the sheet. You get a full page scan in one shot - most of the time.

Greyscale scanners need just one pass of the CCD to finish the job, but when scanning in colour, many low to mid priced flatbeds make three passes to gather red, green and blue (RGB) information. A more accurate method ( and a more expensive one, although its price has fallen over the past year ( is single-pass scanning. A single pass colour scanner either uses three light sources almost simultaneously, or separates a single white light source into the RGB (red, green, blue) components with a filter.

If speed is important ( in other words, if you make more than a few scans each day ( look for a single pass scanner and ask the vendor or reseller about different models' scanning speed. Even at the same resolution and colour depth, some scanners are quicker than others are.

And whichever speed you seek, ask if the scanner's light source remains on constantly. Some units don't turn off their lamps between scans, which makes for more frequent replacement of burned out bulbs. Check, too, on the availability of add-ons such as automatic sheet feeders for high-volume OCR work and transparency adaptors for turning slides into digital images. Most of these can be installed in a few minutes without any outside help.

By contrast, most flatbed scanners themselves connect to your PC through an included 8-bit SCSI interface card, so you may have to wrestle with IRQs and address conflicts during installation and configuration.

If your computer already has a SCSI interface, perhaps for its hard drive or CD-ROM drive, find out if the scanner uses standard SCSI or some more exotic variant, then make sure the vendor provides a suitable Advanced SCSI Programming Interface (ASPI) driver. Some models even include drivers for use over a network, letting you share a scanner throughout a small workgroup.

Scanning the rainbow

Colour rules. And it's cheaper than it's ever been too. If there's even a chance you'll want to digitise and then display or print colour images, get a colour scanner.

Scanners' colour capability, like that of graphics cards, is measured by bit depth. The norm now, 24-bit colour, provides 8-bits of data or 256 different possibilities for each pixel in each of the three colour channels: red, green and blue. That multiplies out to 16.7 million possible colours. Many scanners aimed at graphics professionals, such as the HP ScanJet 3c, are 30-bit devices capable of more than 1 billion possible colours. Some, such as Microtek's ScanMaker III, support a still greater palette ( 36-bit colour.

More isn't always better when it comes to colour depth because it isn't always necessary. A 24-bit or 30-bit colour image will be wasted when displayed in a presentation using 256 colours. And, as you'd expect, the more bits per pixel, the larger the image file. High-resolution, high-colour images can fill a hard drive in a hurry.

And as far as text is concerned, the most accurate OCR involves not 24-bit colour or even 8-bit monochrome (256 grey scales), but one-bit, black-and-white scanning. The Avec 140 HomeScan, for example, is a 1-bit, 200 dpi scanner for line art and OCR that also doubles as a fax machine.

On the other hand, the richer its palette, the more accurately a scanner can capture an image's shadows and colour subtleties. Though a 30 or 36-bit scanner can be overkill when you're printing digitised images on an inkjet, it can work wonders with transparencies. Colour slides have a much greater range of colour qualities than images on paper. When fed through a high-quality scanner with a transparency adaptor, they can produce stunning images.

For most work, though, 24-bit colour is sufficient. Don't settle for anything less. You really don't have to settle, since 24-bits is the current de facto standard. However, don't pay for more unless you're sure you'll use it.

Dots and more dots

Just as you may have 20/20 vision, a scanner might have 400 x 800 vision. Its optical resolution, measured in dots per inch, defines the sharpness of detail it sees.

A flatbed scanner's optical resolution, also called true resolution, is listed as horizontal times vertical dots per inch. A 400 x 800 dpi scanner, for example, divides each horizontal inch of an image into 400 pixels and reads 800 lines of data from each vertical inch. In other words, its motor takes 800 steps to move the CCD one inch, while the CCD itself contains 400 light sensitive elements across each inch of its width.

Some 300 x 300 dpi flatbed scanners are available, but current low-end colour models start at 300 x 600 dpi. The norm today is even higher - 600 x 600, 400 x 800 and 800 x 400 dpi devices readily can be found for less than £1,000. The top end of the general business scanner market is in the 1,200 to 1,600 dpi range. Microtek's ScanMaker IIHR, for instance, features 600 x 1,200 dpi resolution and sells for about £600.

Although higher resolution scanners produce more accurate digital images, they're generally slower at scanning. And the image files they produce are much larger: An image scanned at 600 x 1,200 dpi contains four times as much data as one scanned at 300 x 600 dpi, so you'll need plenty of RAM and hard drive space to edit and store such fine scans.

Nevertheless, a high resolution scanner can be a good match for a high resolution output device. If you're converting greyscale images for printing on a 1,200 dpi laser, for instance, a scanner in the 1,200 dpi range makes sense.

It's important to note that optical resolutions aren't the only sets of numbers you'll find in scanner ads. Most also cite a scanner's interpolated (sometimes called "enhanced") resolution, which can seem stratospheric. The 800 x 400 dpi Umax Vista S-8, for example, boasts an interpolated resolution of 6,400 x 6,400 dpi.

Interpolation is a software scheme typically handled by the scanner driver. It can't actually produce more dots per inch; only the scanner's hardware can do that. But it can trick the eye into seeing a higher perceived resolution via averaging, which means examining adjacent pixels, then creating additional intermediate pixels based on that data. The results include smoother transitions in greyscale images and better quality colour in colour scans.

Interpolation has no effect on 1-bit images, since those pixels are either black or white with no shades of grey in between, and it isn't always a benefit. Some high contrast images can be interpolated into muddy greys and drawings with sharply defined lines can end up looking fuzzy and indistinct. Still, it's a valuable bonus. Look for a scanner that can generate interpolated resolutions of at least 1,200 x 1,200 dpi.

Multifaceted multifunction products

Small offices where desk space and budgets are equally tight are increasingly turning to multifunction peripherals that combine scanning, printing, faxing and copying capabilities. Available from vendors ranging from Brother and Lexmark to Panasonic and Xerox, these all-in-one units typically sell for £800 to £1,000 via mail order.

If consolidation and cost-cutting are paramount, a multifunction peripheral may satisfy you. But there are trade-offs, particularly when it comes to scanning. So far, these scanners are exclusively greyscale, not colour ( with some units limited to 16 or 64 greyscales, though Lexmark's Medley supports 256. Optical resolution is typically 200 x 200 or 300 x 300 dpi, with Okidata's Doc-It 3000 claiming the prize at 400 x 400 dpi.

Frankly, multifunction peripherals' scanning hardware is intended primarily for OCR purposes such as scanning a fax into editable form. Many, in fact, use the same technology to scan and fax.

Multifunction units may give an office everything it needs in one shot, but the potential drawback to buying a "jack of all trades" is the risk of getting a master of none ( a low-powered peripheral that's easy to outgrow. If saving space is the essential issue, you may want to consider one of the compact desktop personal scanners from companies like Plustek instead. Otherwise, with flatbed-scanner prices falling so sharply, it makes better sense to opt for a standalone scanner rather than a multifunction device if you anticipate you'll need to scan more than a few text pages or low resolution, greyscale images. The key is simply to know your needs ( both short and long-term before you buy.

And all the rest

With such a rich lode of scanners to mine, it's likely you'll end up with several models on your shopping list. One way to effectively narrow the field is to evaluate each unit's bundled software. Few scanners are sold without at least one application; most come with a pair or more of programs.

Look first at the scanner's TWAIN driver. A specification developed by a group of hardware and software makers, TWAIN simplifies and standardises the scanning process, letting you capture an image or begin an OCR session from within any TWAIN-compliant Windows application. Most such applications provide an Acquire command in the File menu.

Not all TWAIN drivers are alike, however. Some, such as the DeskScan II driver included with the HP ScanJet 3c, have extra features. These abilities include automatic exposure in which the scanner evaluates the image and sets such things as brightness, contrast and colour for you, which is highly recommended for business users without graphics experience. Other TWAIN drivers, by contrast, present confusing dialogue boxes or seemingly endless menus, and a few scanners provide no TWAIN driver at all.

Many scanners now also have a colour management system for matching scanned colours with those you see onscreen and from your colour printer. The process of colour matching differs among scanners. Some units offer software controls such as Microtek's excellent Dynamic Colour Rendition utility. Others provide colour calibration targets for you to scan and then print. However it's done, some kind of colour management system is vital for generating colour separations.

Beyond their TWAIN drivers and colour management systems, software bundles typically include an image editor for manipulating, adjusting and enhancing the visuals you slap on the scanning glass. It also needs an OCR package to finish the job of turning paper pages into editable electronic documents; or both, to make your new scanner instantly usable right out of the box. Some models come with a utility that lets you use your scanner and printer together to create a virtual copier.

And some scanners, marketed as document processors, include a document imaging package in the mix, letting you put a dent in the pile of paper that threatens to bury most offices. Document imaging, which combines OCR with organisation and retrieval tools stolen from enterprise-wide document-management and routing systems, converts paper to digital data, saves it to your hard drive, and summons it to the screen as quickly as you can type search requests.

After a document is scanned, its OCR converted text data is indexed and saved to the hard drive, usually along with a thumbnail image file of the original document. The finest programs also let you browse lists of documents ranked by how closely they match your search criteria. One of the smartest document imaging package is Caere's PageKeeper, which processes email messages and incoming faxes, as well as paper-based documents, using Caere's highly accurate OmniPage OCR engine.

Finally, don't be duped by the quantity of software titles bundled with a scanner. Look for quality, as indicated by friends' or magazines' recommendations instead. Many scanners, particularly those on the lower end of the price spectrum, come with "lite" versions of popular image editors or other programs, or unwieldy OCR samplers that lack the accuracy of up-to-date versions. A second-rate bundled application adds nothing to the bargain if it makes you pay for more powerful software out of your own pocket.

Scanning, scanning, scanned

The days when scanners were solely the domains of sophisticated design shops are long gone. Thanks to steadily falling prices, more powerful software and higher speeds and resolutions scanners are taking their place beside many a PC.

Handheld units are facing a slow but sure demise, squeezed on one side by affordable, high-quality flatbeds, and on the other by alternatives such as personal scanners. Otherwise, scanners' prospects have never been brighter. Giving your PC a good pair of eyes is easier ( and cheaper ( than ever before.

Compiled by Paul Phillips

( Caere Corporation, 1999

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This was first published in September 1999


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