Genealogists and millions of others have saved hundreds of millions of digital photographs on their hard drives as well as 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.
NOTE #1: The abbreviation "JPEG" stands for Joint Photographic Experts Group, the name of the committee that created the standard. The group was organized in 1986, issuing a standard in 1992, which was approved in 1994 as ISO 10918-1. The JPEG standard specifies both the codec, which defines how an image is compressed into a stream of bytes and decompressed back into an image, and the file format used to contain that stream.
NOTE #2: Several compression methods have been developed for graphics images, including JPEG, GIF, and PNG. However, JPG remains the most popular for storage of photographs. I will focus only on JPG. Most of the statements in this article apply equally to all the other compressed formats.
JPG has become very popular for very good reasons. Storing images in JPG format consumes much less disk space than many other file formats. That was very important some years ago. However, as disk prices have plunged, the need to squeeze as much out of each kilobyte as possible has declined.
As good as JPG is, we do need to keep in mind that it also has significant drawbacks.
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