Unlike film, where the same transparency can be used in different situations, digital files are usually made for specific uses.

Files are classified by format, size, and color space. File size is a function of the physical width of the image multiplied by dots per inch (dpi) or pixels per inch (ppi). For example, a 4 x 5 image rendered at 300 dpi, for quality four-color printing, becomes a 5.4-megabyte file. Rendered at 72 dpi (typical monitor screen resolution), file size is only 311 kilobytes.

The common file types are "tiff" (or .tif) and "jpeg" (or .jpg). Under normal conditions, we deliver images to our clients as 50-megabyte RGB (red/green/blue) tiffs and 1-megabyte jpegs.

The much larger (and therefore higher-resolution) tiff file is used for making photo-quality prints or for taking an image to press for printing. Because of their size, tiff files cannot be easily emailed and may be difficult to open on computers with limited memory.

The much smaller jpeg files are easy to email, they look good on a computer monitor, and therefore can be used on your web site. But because so much information is removed from the image in the process of compressing it to the smaller size, jpegs lack the sharpness necessary for a brochure or magazine ad.