Proper scanning techniques can help scan quality on different types of documents.
Modern scanners are almost universally high-quality digital imaging devices. Depending on the purpose of the scan and the type of document being scanned, certain optimizations while scanning a document can help improve your final results.
Scanning Text for Optical Character Recognition (OCR)
If you are scanning a book, magazine, newspaper or any other printed text document for the express purpose of OCR, several things can help the overall process. It is very important that the page you are scanning be aligned square with the edges of the scanner. Modern OCR can straighten pages, as can some scanner software interfaces, but your overall results will be better if the page is straight in the first place. Make sure that you scan the document as a black and white image; this will reduce the amount of data that the OCR program will need to process. Ideal resolutions for OCR will usually range from between 200 and 300 dots per inch (DPI).
Scanning Images & Photographs for Online Use
Most current scanners can capture images at far more detail than is required for posting or displaying photographs or images online. Most current model scanners are capable of scanning at anywhere between 1,200 and 9,800 DPI. Some scanners are capable of even higher resolutions. Most monitors offer something in the neighborhood of 96 DPI display resolution. Computer monitors cannot display an entire image when it is scanned larger. Scanning large images also uses more memory and hard disk space for storage, not to mention bandwidth for transmitting the image. If you are scanning a standard four inch by six inch photograph for online display on a site like Facebook, set your scanner resolution to somewhere between 75 DPI and 100 DPI. That resolution will give you a good image quality that will not be so large that it downloads too slowly and suffers from cropping in a browser.
Scanning Images & Photographs for Printing
When you email someone a low resolution photograph, they may not be able to print the photograph at high quality. If you want to scan a photograph or image for emailing to a person who may later print that image, it is best to scan the photograph at 300 DPI. 300 DPI images are likely going to be too large to display well in a web browser or on a monitor, but the additional image data is required for higher quality printing. If the file size is too large for convenient emailing, try saving the image as a JPG and reducing the JPG quality to around 50 percent.
