File Compression

There are two types of file compression, "lossy" and "lossless"

Lossy compression actually changes some of the original pixels and some details are lost. The most common type of lossy compression format is JPG. While the original JPG image out of a digital camera is fine, every time the file is saved again, detail is lost. If the same file is saved as a JPG a few times, significant quality is lost and cannot be recovered. Valuable originals should always be saved in a lossless format, like TIFF or RAW. TIFF files can be edited and saved any number of times without loss of detail because the compression does not alter any pixels. The trade off is that TIFF files do not compress as well as JPG.