How to choose and use a scanner. (Compute's Getting Started with Desktop Graphics) (Buyers Guide)
by Steven Anzovin
Imagine how dull newspapers and magazines would be without photographs. Computer graphics, desktop publishing, presentations, and multimedia on your PC can be just as drab without the richness of photographic imagery. To get exciting real-world pictures into your computer, you need a scanner. It's a device that reads the patterns of lights, darks, and colors from photos and art and converts those patterns into computer-readable information.
Scanners used to be high-priced items that only succesful desktop publishers could afford. Today even color scanners can be relatively inexpensive and easy to use. There are four things to keep in mind when choosing a scanner: resolution, color or gray-scale capability, hardware type, and quality of the scanning software that comes with the scanner.
Most scanners today can scan in an image at a range of resolutions from 75 dots per inch (the approximate screen resolution of VGA) to a maximum resolution of 400 dpi, which is higher than the standard laser printer resolution. (That doesn't mean that you'll see the image on your screen at 400 dpi, only that it can print at that resolution.)
High-end color scanners can scan at 600 dpi, but the extra expense of such units is only justified if you plan to print your scans with a high-resolution color imageselter. Also, such high-resolution color scans require lots of mass storage and RAM, so it makes sense to scan at the minimum necessary resolution--75 dpi for multimedia, and no more than 300 dpi for laser-printed art.
Color vs. Gray Scale
Then there's the question of whether you need a grayscale or color scanner. Grayscale scanners convert the colors of the scanned art into as many as 256 shades of gray; some lower priced units scan only 16 or 32 gray shades and convert the image into an apparent 256 grays through software.
The quality of such interpolated images isn't as high as those created with true gray-scale scanners--the more true shades of gray, obviously, the more the scan will look like the original art. Top of the line 24-bit color scanners can produce photo-quality images containing up to 16.7 million colors.
The two most common types of scanner hardware are hand-held scanners and flatbed scanners. As you might guess, hand-held scanners are small, low-cost units held in the hand and stroked over the document to be scanned. To produce large images, the narrow scans of hand-held scanners-generally no more than about 4 inches wide--have to be stitched together using software.
It takes skill and patience to accurately scan with a hand-held scanner. You have to scan at just the right speed and in a straight line. And so these units are favored by people who scan only occasionally or who scan only small art.
One-popular gray-scale hand-held scanner, the Logitech Scanman Model 256 for Windows (Logitech, 6505 Kaiser Drive, Fremont, California 94555; 510-7958500; $449) has sophisticated image-merging software that makes it relatively easy to scan art larger than can be handled by most flatbeds.
Flatbed scanners resemble small photocopiers, and work in much the same way. The scanning head and light read the image as they pass underneath the art, which is positioned face down on the glass scanning bed called a platen. Flatbed scanners generally produce images that are superior in quality to those from hand-held scanners, and most flatbed scanners can handle images up to legal size with one pass. That's why flatbeds are the choice of serious desktop publishers and graphic artists. But that versatility and quality comes at a price. Flatbeds generally cost three to five times as much as hand-held scanners.
Representative of top-quality flatbeds is the ScanJet llc (Hewlett Packard, 800-752-0900). With 400 dpi resolution, full gray-scale and color capabilities, quick scanning, software enhancements that bring the perceived printed resolution of images up to 800 dpi, and a street price of about $1600, the ScanJet IIc is likely to become the flatbed industry standard.
One scanner that takes a different approach is the Chinon DS-3000 Chinon America, 660 Maple Avenue, Torrance, California 90503; 800-441-0222; $995). Combining the mechanical simplicity of a hand-held unit with the stability of a flatbed, the DS-3000 has a scan head fixed on an arm over the platen and can scan not only flat art, but also three-dimensional objects up to two inches high.
Even top-notch scanners are worthless without software to drive them. In fact, the software that comes with a scanner can make using it a joy--or a pain. At a minimum the scanner software should allow you to preview the image to be scanned, select a resolution and the number of grays or color, and save the scan in a common graphics file format (usually TIFF) that's accepted by graphics and desktop publishing programs. More advanced products automatically correct for a skewed image and allow adjustments for contrast, brightness, and color correction.
Some scanners come with image-editing software. Though if you're running Windows, you'll probably want a feature-packed, third-party image editor such as PhotFinish (ZSoft, 450 Franklin Road, Suite 100, Marietta, Georgia 30067; 404-248-008; $199) or PhotoStyler (Aldus, 411 First Avenue South, Seattle, Washington 98104; 206-628-2320; $795). Import a high-resolution color scan into either program, and you can apply a wide range of filters, masks, brushes, and distortions to create just the look you want. Then the image can be output as a color-separated file for desktop publishing.
The more your image-editing software can do for you, the less time you'll spend tweaking your scans to get them just right, and the more time you can spend employing your scans for maximum graphic impact.