What is a Digital Photo JPEG File

Digital photos are stored as files on memory cards and computer hard disks. They can be stored in different file formats (each format has a unique file extension). Digital photo files can be compressed to save storage space and can use a standard or a proprietary format.

Digital photos are saved as digital files on electronic media. These digital photo files are a collection of bytes. JPEG is a standard file format for storing such digital photos. The JPEG format supports compression and allows very efficient high quality storage of digital photos. When using the JPEG format any software from different vendors that adheres to the standard can create and process JPEG files.

JPEG - Joint Photographic Experts Group

The JPEG file format was designed by a special industry group for the purpose of storing and compressing high quality digital photos. Later on JPEG became an ISO standard and it is probably one of the most popular formats for storing digital photos today. JPEG files are also known simple as JPG files (named after their common file extension .JPG).

The design goal of the group was the efficient storage of digital photographic files while maintaining their original high quality (or quality which is as close as possible to the original one). JPEG files can support lossless compression but since lossless compression is inefficient when compressing digital photos it is hardly used. In most cases JPEG files use lossy compression to efficiently represent digital photos.

It is easy to understand the motivation for such efficient compression by using an example: Digital photos files are built of pixels each one has a value representing its color and intensity. Each pixel occupies 3 bytes (one for Red, one for Green and one for Blue - representing the color and intensity of the pixel). If you shoot a photo using an 8 mega pixels digital camera the photo will have 8000000 pixels each one occupying 3 bytes. The total file size would be 8000000*3=24000000 or 24Mbytes. This is a very big file. Big files are hard to manipulate they take a long time to send by email, they occupy large storage space and they take longer to load. If that same file was compressed into a JPEG digital photo file its size would reduce to about 3Mbytes - a much more manageable file size.