Scanners: not a black-and-white choice anymore - overview to evaluations of four scanning devices - Hardware Guide - Buyers Guide

Home Office Computing, Feb, 1992 by Steve Morgenstern

Scanners are cool.

I know it's a non-technical, retro word, but there is something cool about the ability to take an image from a piece of paper, suck it into your computer, and incorporate it into a report or proposal, a piece of correspondence, a database file, a desktop-publishing project.

And right now, scanners are hot. Inexpensive handheld scanners have become serious graphic-input tools. At the same time, prices for full-size flatbed scanners are tumbling, and features formerly found only on top-of-the-line models are now available in mid-priced units. Gray-scale and even color scanners are no longer the exclusive domain of graphic-arts professionals. And as we continue to move from computers that comfortably handle only words and numbers to graphically capable systems that make illustrated documents easy to prepare, our need for image scanners grows. You'll note that IBM-compatible scanners are overwhelming Windows-based--so your system has to be up to par. Logitech's is the only scanner reviewed here that can scan without Windows, using its DOS Scanning utility from the C:>promt.

In this month's hardware guide, we'll take a close look at four recently introduced models, each of which represents a significant new direction for scanner technology. We have also prepared a chart incorporating 11 currently available models from major manufacturers that are worth evaluating.

By way of background, you should undestrand the two key factors used in categorizing scanners: size (flatbed or handheld) and image type (black and white, gray-scale, or color). While sheet-fed scanners are still an option, we're seeing more flatbed and handheld options than ever.

FLATBED SCANNERS

A flatbed scanner works in much the same way as a photocopier: you place the original on a flat sheet of glass, and a light-sensitive bar scans beneath it.

Flatbed models can scan full 8.5-by-11-inch sheets, and some models can also handle 14-inch (legal-size) originals. This is important both for large illustrations and for optical character recognition (OCR), the technology that allows you to scan in a printed page and have software "read" the words into a text file.

Since the flatbed's scanning mechanism is pulled across the image by a motor, the movement is precise and there is little chance of image distortion. And if you get into multipage scanning projects (common in OCR applications), you can add a document feeder to most flatbed scanners.

Flatbed scanners do take up a significant chunk of desktop real estate--most units are more than a foot wide and nearly two feet long. They are also expensive when compared to handheld scanners: about three times the price for models with similar gray-scale or color capabilities.

HANDHELD SCANNERS

Handheld scanners have distinct limitations when compared with flatbed models. The size of the images you want to scan is clearly the most pressing concern. Most handhelds are four inches wide, and the width of the image scanned is effectively limited by the width of the scanner. Some models come with software that allows you to "stitch" two separate passes together to create a full-width document scan (see the review of the Logitech 256 that follows), but this is inevitably time-consuming and often inaccurate.

There's also a certain level of manual dexterity required to use a handheld scanner effectively. You are the motor here, and if your hand veers a little, the resulting scan will have a psychedelic ripple effect.

On the other hand, a good handheld scanner is an excellent value. If you stick to relatively small originals and use the equipment properly, you can often achieve results indistinguishable from those obtained with a flatbed scanner at a fraction of the price.

BLACK AND WHITE, GRAY-SCALE, COLOR

Both handheld and flatbed scanners come in three varieties. The simplest, least expensive versions record images only in terms of black dots and white dots. This is perfectly adequate in some cases--a line drawing or text document only has black and white in the first place.

The challenge starts when we want to scan continuous-tone originals. These are images that contain shades of gray or color in addition to black and white.

A "black-and-white" photo is actually [TABULAR DATA OMITTED] composed of a multitude of gray shades and very little that is pure white or pure black. A scanner with only black-and-white capability, though, must translate those gray areas into patterns of black and white dots that look gray when they're reproduced on paper.

Optical illusion. A gray-scale scanner has the ability to distinguish up to 256 shades of gray--the accepted standard, currently--a far cry from simple black and white. Keep in mind, though, that it's also a far cry from the quality a standard dekstop laser printer can effectively reproduce. For practical purposes, a 300-dot-per-inch laser printer is limited to reproducing about 16 shades of gray while retaining an acceptable level of image detail. In order to make use of the full gray-scale scanning capabilities of today's scanners, you have to output the file on high-resolution printers.

There is another significant advantage to gray-scale scanning, though--the ability to edit the captured image. With software either supplied with the scanner or purchased separately, a gray-scale image can be resized significantly and still maintain its sharpness. You can also enhance the image in important ways, increasing sharpness or manipulating image brightness and contrast, and retouch the image to eliminate imperfections or add highlights.

Color-image scanning is conceptually similar to gray-scale scanning. A 24-bit color scanner (such as the Hewlett-Packard ScanJet IIc) can distinguish more than 16 million colors, and even a more modest color hand scanner (such as the Mouse Systems PC PageBrush/Color) can capture 4,096 shades.