Scan Resolutions for the Family Photo Collection

Suggestions for scan resolutions vary widely.

The resolution needed for a scan is largely a function of the intended use of the scan. If one is scanning images primarily for digital archiving purposes and the scans are being made of roughly 4 x 6 inch prints, I would argue that scanning at 600 pixels per inch is typically plenty.

In most cases, a planned or potential future use of the scan is to create another print of similar size or a popular sized enlargement. The key here is to understand the general agreement that professional photo quality is regarded as 300 image pixels per inch spread onto the print area. It is also generally accepted that most people will be perfectly happy with printing results of 150 pixels per inch and perhaps lower. (Note this is different than dots per inch, which denotes a printer's ink laying capability.)

Using this math, if one scans a 4x6 print at 600 pixels per inch, one can then spread these image pixels over a printed area of 8 x 12 (two times the height and width of the original) at 300 pixels per inch or over a surface of 16 x 24 at 150 pixels per inch. Therefore, one retains plenty of future printing flexibility with scans at 600 pixels per inch of scan resolution.

Professional online scan services often offer a choice of 300 or 600 pixels per inch.

Another consideration is the file format of the scans and compression levels used.

For a more detailed explanation of pixels, pixels per inch, and dots per inch, visit the article on Digital Basics at LocalArchiver.com. For more information about scanning and a discussion of other considerations, visit the Scanning Guide at LocalArchiver.com.