The process and applications of a scanner are relatively simplistic. Scanners are like a copier - open copier, place file face down, close the cover and scan.
A critical part of any scan is determining the proper resolution, or dpi (dots per inch) setting. Most scanning software allows you to select from a range of settings measured in dpi (dots per inch). Individual settings depend on the quality of the scanner you’re using and technological possibilities are expanding all the time.
Generally speaking, the greater the dpi (or higher the resolution), means a better quality scan which is a larger file. A typical 400 dpi color scan can be as large as two megabytes, whereas a 100 dpi black and white scan is somewhere between 50-100 kilobytes. There is also a major difference in the smoothness of color shading. The edges of the scanned picture become more jagged and irregular when using a lower resolution setting.
The advantage to scanning in pictures at a lower resolution is that the files are not as large, and can be easily attached to an e-mail. The disadvantage, however, is that the lower resolution creates a lower quality picture - this is bad for printing purposes. Photo images found on the Web are usually scanned at 72 dpi. While they look great on your screen, these photos will not print on a color printer very clearly. Scanning for print should be 300dpi or higher.
A general rule when scanning. If you need a quality of 300dpi for printing, you need to scan the image in at 300 dpi. If you need to enlarge the image by twice the size (200%) - then you will need to scan it at 600dpi. If the image triples in size (300%) - then you will need to scan at 900 dpi.
Black & White/Gray Scale Scanning
When scanning black and white images or text, the resolution needs to match what the printer requires (300 dpi). Whether it’s photos or text, contrast is just as important as resolution. Sometimes you’ll need to darken the black or grays to add contrast against a white background. Adjusting contrast can cause otherwise unnoticeable scratches or particles to appear. Using Adobe Photoshop®, you can easily increase or decrease contrast once a scan is completed.
Another thing to be aware of is the quality of the original you are scanning. The scanned picture can never be better than it’s original, and you must keep in mind that there are always minor deficiencies, scratches, or other imperfections that will be enhanced by the scan. Keeping the glass on your scanner clean, and double-checking for wrinkles, smears and other debris on the original will usually lead to a high-quality scan.
In scanning different kinds of media, the best thing to do is experiment. Once you have some of the basic principles down, you’ll start to see more and more ways to apply them, and even begin to think of new things you might want to try. Play around with scanning objects other than pictures or documents. Most mid-range scanners can capture almost anything that will fit on the glass.