What are the differences between PICT, TIFF, and JPEG images?
Answer: Of the three formats, JPEG (.JPG) images are the most commonly seen, as most photos and images on the Web are JPEGs. JPEG images are compressed images that maintain the full range of color in the image, but are compressed in their clarity. JPEG images that are significantly compressed look blocky and fuzzy. The amount of JPEG compression is measured by a quality number and is inversely proportional to the file size. For example, a compression level of 90 (out of 100) will look nearly identical to the uncompressed image, but won't reduce the file size very much. A compression level of 10 will reduce the file size significantly, but the quality of the image will be rather poor. Photoshop's default setting for JPEG Web images is 60. Also, JPEG images cannot include layers.
PICT files can be uncompressed or compressed using the JPEG compression described above. Most PICT files that are saved uncompressed are still smaller than several other image formats because of the PICT format's internal compression algorithm. It is best suited for images with large areas of the same color, which can be saved most efficiently. Like JPEG images, PICT files cannot include layers, but can include some path information from vector images. Since PICT was initially a Macintosh format, some Windows programs cannot open PICT files.
TIFF (.tif) images are more compatible with multiple platforms than PICT images are and can be compressed of uncompressed. TIFF compression can be done using JPEG, LZW, or ZIP compression techniques. Only bitmap data can be stored in a TIFF image, meaning no vector data is saved within a TIFF file. However, recent versions of the TIFF format can include layers like Photoshop documents can. Because of the high quality of TIFF images, it is an ideal format for publishing and other print industries.