NWA-PCUG 12/99 NewsLetter Article 18861 N. Hwy 112, Springdale, AR 72762-9303 Scanning Basics by Tom Monturo, Mid-Hudson Computer User Group P.O. Box 1962, Poughkeepsie, NY 12601-0962 The scanner you buy is a hardware device. It will usually come with two kinds of software; one a photo or graphic processor for handling graphics, and the other an optical character recognition (OCR) package for recognizing characters from printed matter.Scanners will do two different jobs: * they scan graphics, either in color or in black and white, and place the graphics into files for your computer, or * they read documents and turn them into files that your word processor or text editor can process. Resolution Resolution is generally described in "dots per inch" or dpi. Unfortunately there is a great deal of confusion in the term as it applies to screen, scanner, and printer. A screen resolution of 800 x 600, typical of 15" monitors, applies to maximum pixels displayed, where a pixel is the smallest visible unit on the screen. Such a monitor has an actual horizontal screen size of about 10.5". At 800 pixels divided by 10.5", its resolution is about 75 dpi. Scanner resolution is a specification that describes the maximum number of dots that can be sent to the computer. Since there is a practical maximum of about 300 Charge Coupled Devices that can be mounted on the scanner light bar, any claimed resolution that exceeds 300 dpi must be interpolated. That's not necessarily bad, but it does depend partially on the quality of the scanner software. Printer resolution is also expressed in dpi, but can be misleading since printers must place a series of dots on the paper to create the illusion of shades of gray or, for color printers, to show variations in color. A 600 dpi laser printer may place anything from 0 to 600 dpi on a line to express 256 shades of gray from white to black. You choose the resolution you wish when you scan material. Do not assume that you should scan everything that will be printed at the same maximum resolution of your printer, i.e., if you have a 600 dpi printer, don't assume you should scan at 600 dpi. Here are some suggestions for choosing scanner resolution. When scanning gray scale or color images, using either a color or a black and white printer: * with a 300 or 360 dpi printer, use a scanner resolution of 50 to 100 dpi. * with a 600 or 720 dpi printer, use a scanner resolution of 100 to 150 dpi. * when scanning black and white images or for OCR, use the full scanner resolution. Handling Graphics At minimum, if your scanner software permits - and most do - adjust the image level or tone before sending your graphic image to your photo enhancement program. Then, if necessary, use a sharpening filter. An Excellent Source of Information on the Web is Wayne Fulton's "A Few Scanning Tips" found at http://www.scantips.com. This article is brought to you by the Association of Personal Computer User Groups, an international organization to which this user group belongs. The author, the late Tom Monturo, was the editor of microCHIP (micro Computer Happenings In Poughkeepsie), the newsletter of the Mid- Hudson Computer User Group in Poughkeepsie, New York.