If you only need to grab some scans to send by email or put up on the Internet, then you can get the job done with a scanner in the $100 price range.
If you are a professional photographer, or you want to print your scans to photographic paper or use them in commercial printing processes, then you’re shopping in the $800 to $2,000 range.
Functionality and specialization are the two price-drivers for scanners. Your first step is to determine which of the three basic scanner types is best for you.
A flatbed scanner scans photographs, clippings, book pages, small 3-d articles, etc.
Specially designed to scan negatives, slides, and transparencies.
Does the work of both a flatbed and a film scanner.
Some film scanners are highly specialized so make sure that the one you are considering supports your preferred film format.
The major quality determinator for any scanner is the optical resolution rating. Not only does the resolution dictate the quality of the scanned image’s appearance, but it determines the maximum size print that can be produced from the scan.
Optical resolution ranges from 300 Dots Per Inch (DPI) up to 4000 DPI and higher. Anything below 600 DPI is not worth considering at all and an optical resolution of 2700 or better should handle most projects that the average photographer will encounter.
Make sure that the scanner’s DPI rating is the true optical resolution rating and not the “interpolated DPI rating” which requires software to achieve. DPI is one of the features that drives up the cost of a scanner but it is a critical performance item for you so it is worth spending time on.
Color depth, a measurement of the number of colors that the scanner is able to process, is another performance measurement that’s worth understanding. In scanners color depth is measured in bits. A 24-bit scanner is OK but 30 bit is better. Pro photographers may want to consider 36 or 48-bit models.
Another performance item is the scanner’s density range rating. Density range refers to the tonal quality that a scanner is capable of capturing. The higher the range the better the image quality. A good scanner will have at least a 3.2 rating. Ratings of 3.4, 3.6 and higher are even better.
Although you also need to consider hardware compatibility and bundled software issues, the last of the most important performance items is scan time speed which is measured in pages per minute or PPM.