A digital photo is composed of pixels. Each pixel represents a single dot in a photo that has a value. This value represents the pixal's color and intensity. Usually a pixel is represented by an RGB value (Red, Green and Blue). Digital photo files can be very big, i.e. 8000000 pixels this can make an image difficult to load and store, however, it can be compressed using the right technology.
The problem with compressing an image, however, is that oftentimes it loses quality and metadata. This is not substancial for long-term preservation of a digital image. For digital preservation it is important that our images are preserved in the proper file type to avoide this loss.
There are two types of compression technologies, lossless and lossy:
Lossless compression (TIFF Files): Lossless compression means that if you compress a file and then decompress it the decompressed file would be the exact copy of the original file. In a lossless compression no data is lost in the process the compression.
Lossy compression (JPEG Files): Lossy compression means that if you compress a file and then decompress it the decompressed file would be slightly different than the original file. The compression software represents the file's data more efficiently, however, it also removes data.
For archival purposes it is best to preserve digital photographs as lossless, TIFF files. These images maintain their quality and data, offering a more stable option for preservation. Many people opt to use JPEG to store their images because the file size is smaller, and therefore takes up less space in their storage, however, they risk damage to the images if they are stored as JPEG for the long term.
Ideally, all images would be created and preserved as TIFF. You can use programs like Batch Converter 2.1 and IrfanView to batch convert any JPEG files you have to TIFF. Although these images are not as high of quality since they started out as JPEG, they will be better preserved in the future if they are maintained as TIFF files/