There are various types of digital graphics files available. Some are best suited for only certain applications and each require specific handling.
For additional help with optimizing web images, consult the web style guide.
EPS (Encapsulated PostScript) files are vector graphics--which means they can be scaled up or down infinitely. EPS files are best used for high resolution (either image-set or reproduced on PostScript printers) print projects or for creating graphics for other applications.
TIFF (Tagged Image File Format) files are typically used for high-resolution printed pieces. TIFFS can be scaled down, but not scaled up (a TIFF can never be made significantly larger than its "native" size without loss of image quality).
Named after the Joint Photographic Experts Group, JPEG files are the most common photographic file type on the web. JPEG images can be compressed to allow quick-loading, but it is important to not compress the images to the point of degradation. JPEGs can be scaled down, but cannot be significantly enlarged without loss of image quality. When using a JPEG on the web, it is best *not* to use height and width HTML tags to resize the image down. Resize the image in a graphics program first.
GIF (Graphical Interchange Format) files are used commonly on the web. These files are best used for black and white or block-color images. GIFs do not work well with gradation or photographic images. GIFs cannot be resized in their native format.