Scanners add art and color to school documents.
Graphic scanners offer a variety of services for instructors, students and administrators alike. They help incorporate art work such as line drawings, commercial clip art, illustrations or 3D objects into tests, district publications, student newspapers and other documents.
Although the technology has taken off, particularly in the realm of color, other restrictions such as RAM requirements, price and compatibility make choosing scanners a thought-provoking process.
Types of Scanners
There are three types of graphic scanners available--flatbed, hand-held and 35mm slide scanners. Flatbed scanners are well suited for scanning large, page-sized flat art. These units deal in monochrome, black-and-white or color, and can scan from a variety of sources.
A variation on the flatbed scanner design is the overhead flatbed. The difference is that overhead units are "open air" and scan optically. The optical mechanism is located on a tower that passes over the source material. Overheads often offer better resolution and boast higher dot-per-inch ratios, but they rely on ambient light to illuminate originals and may tend to produce uneven contrasts.
Hand-held models are small in design and are therefore most useful in scanning small images from flat originals. Their other benefits include price, ease-of-use and flexibility. Hand scanners can scan books, pamphlets and even wallpaper designs.
One problem inherent to its size is the hand scanner's small scanning width. To scan large images, multiple passes need to be made then "sewn" together. When using the hand scanner, one must be careful to scan straight down without slipping. If the path is curved, the image will be distorted. Software is usually packaged with these scanners to help meld images back into original form.
Slide scanners scan 35mm transparencies. They are ideal for high-end publication purposes but, because of their price and relative scarcity in the educational arena, will not be treated here. While slides are easier to handle, store and transport than print originals, slide scanners are designed mainly for desktop color separation.
A few terms must be explained to completely understand how scanners compare to each other. First, there is pixel depth, which is the number of bits assigned to each pixel to define its color or grey level. This attribute is related to resolution, a measurement of dots (pixels) per inch (dpi). The higher the resolution, the better the scanner is at registering detail.
Some scanners can achieve higher resolutions than what the manufacturer states. A method called interpolation averages an image's grey-scale values and puts extra pixels between existing ones to smooth out an image. Keep in mind that scanner resolution should be kept in line with the resolution of the output device--a 600 dpi scanner would be superfluous if the printer has a maximum resolution of 300 dpi.
The number of shades, be they grey scale or color, depend on the amount of internal memory the scanner devotes to each pixel. Originally, scanners used only one bit per pixel, and therefore printed in only black and white. The more bits per pixel, the more shades of grey or colors that are produced, resulting in a more realistic image.
To produce varying levels of black and white, one-bit scanners use dithering, a technique that combines juxtaposed black and white pixels into patterns that look like halftones. The resulting file takes up less memory than grey-scale image files, however the image is locked and is nearly impossible to edit or resize.
All colors in the visible spectrum consist of three or four primary colors. In color scanning, the RGB model--with red, green and blue as primary colors--is most often used. Scanners read each component color in an image in three passes, first red, then green, then blue.
Color graphic scanners have, due to technology improvements, come of age. Initially hindered by poor software and the lack of viable output devices, these scanners are now aided by color image-editing programs and output devices such as color laser, dot-matrix and thermal printers. Color technology has even begun to trickle down to hand scanners.
In addition, some software vendors have packages that let users scan color images with black-and-white flatbed scanners. One such program, ColorSet from Studiotronics of Winter Park, Fla., requires that an image be scanned three times, using a different filter for each pass. The software then combines the three images into one.
Most scanners will save scanned images directly to the computer's hard drive if enough room is available. The larger an image is, in terms of physical size, the more memory it will take up; color images take up even more disk space. For example, a 4" x 5" grey-scale image with 64 shades that is scanned at 300 dpi will take up 1.3MB of memory. The same image scanned in color with 16 million plus shades can take up 5.3MB, according to MacUser Magazine's testing lab.
All in all, scanners help add a splash of life to otherwise dry or plain documents. The type of scanner best suited for a particular application will depend on the school's budget, type of computers and other peripherals to be used in conjunction with the scanner, the type of material that will most probably be scanned and the need for color and/or degree of detail. Regardless, there is a plethora of scanners to choose from, satisfying a range of needs.
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|Publication:||T H E Journal (Technological Horizons In Education)|
|Date:||Oct 1, 1990|
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