Third, you'll need to choose a storage media suited to the expected future use of the pictures. If you can't determine ahead of time the future use for your scans, then you will want to retain as much fidelity to the original image as possible. Given the limits of your computer to process images and the limits of your media to store image files. Choosing the Right Scan Level Scan level refers to the combination of scan resolution and color depth that is right for your purpose. Scan resolution is the number of dots per inch available from the scanner.
Color depth is the range or number of individual colors the scanner can discern and record.
If the picture is for use on a computer screen then the resolution should match the screen resolution and ability to display colors. This would currently be considered low to medium with a moderate range of colors. If the picture is to be stored for archival purposes, the highest scan level your storage medium can reasonably process and store should be used. The rule is to scan at the resolution required by your intended output device. If your pictures will be used as part of a family album on the web or in a genealogy database, you should save them in the JPEG format.