The following is a Plus Edition article written by and copyright by Dick Eastman.
Genealogists and millions of others have saved hundreds of millions of digital photographs on their hard drives, in the cloud, and on CD-ROM disks. Perhaps the most popular file format for digital photographs is JPG (or JPEG), a commonly used method of compression for photographic images. The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. JPEG typically achieves 10 to 1 compression with little perceivable loss in image quality.
JPEG is the most common image format used by digital cameras and other photographic image capture devices, such as scanners. It is also the most common format for storing and transmitting photographic images on the World Wide Web.