Selecting a Resolution
Scanner resolution is measured in dots per inch (dpi). The resolution establishes the quality of the scanned image. Typically, a higher resolution will result in a sharper image. However, depending on what you plan to do with an image, scanning at the highest available resolution could just be overkill, resulting in unnecessary used space on your computer’s hard drive (higher resolution means larger file sizes).
If your sole purpose is to email your photos or post them online and you have no intentions of printing or editing your photos, 72-100 dpi will work just fine. The scanned file size will be small, reducing the time it takes to download or email an image (ideal for those with bandwidth limitations or those who use a dialup internet connection).
Scanning at 300 dpi is a good choice for those who wish to print photos no larger than 5x7. This is a decent resolution to use for scanning and archiving, it also provides enough quality for restoring and editing your photos.
600 dpi and higher
Scanning images at this level means very large files which will use a lot of your computer’s storage - think 30 megabytes (MB) and beyond! You should scan at the highest resolution if you plan to print your photo larger than 5x7. It’s also a good idea to scan sentimental or important photos at your scanner’s highest resolution so you won’t forfeit any detail or quality of the photo. Because of the large file sizes, you should really consider saving these images onto an external storage device, such as a CD or DVD.