Publishers' FAQ > Production and Design > Please help me navigate the jungle of image file types! TIFF, EPS, JPEG... What do I use when?

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See the extremely clear and helpful article by Bryan Chamberlain for explanations of bit depth among other things. (What's the difference between an 8-bit image and a 24-bit image? An 8-bit image only contains up to 256 colors while a 24-bit image can have millions.) The charts defining bit depths and showing the bit depths, vector/raster type, and compression of various file types is helpful.

The discussin of raster vs. vector images in Mike's Sketchpad is very clear with helpful illustrations. Raster, or bitmapped, images are defined by pixels. Most common formats are bitmaps. Vector images, which are defined mathematically by points and paths, are best used for line art and type for print output, since it's hard to hide (or anti-alias) a bitmapped edge on these kinds of images. When you're creating images for the web, you have no choice but to anti-alias your bitmap type and line art.

See John Wurtzel's article on Webmonkey for detailed discussion on when to use jpeg and when to use gif on your website.

It's a bit old (1997), but if you want more information than you ever wanted on graphics file formats, check out the Graphics File Formats FAQ.

The Graphics Software guide at about.com has useful links.

Scanning tips by Wayne Fulton and Michael Sullivan contain discussion of file formats and when to use which one.

For those with Macs, check out Graphic Converter by Lemke Software. It can open and convert many, many file formats. It's shareware but you can get a free demo if you are desperate to open some mysterious file type.

Six common file formats for publishers:

BMP. Windows-specific image format. Don't use for print or web.

EPS. Encapsulated PostScript. The standard file format for printing line art and other images (e.g. company logo) where it's important to use vector type images rather than bitmap. Although EPS guarantees a clear print out from a Postscript printer, it's often difficult to get an EPS image to display properly on your monitor.

GIF. Graphics Interchange Format. Compressed image file that is not platform specific and so often used on the internet. Use the gif format when you are working with an image that has a lot of flat color, since it's very good at supporting 8-bit an under images. GIF files can be animated and interlaced (i.e. made so that they are loaded onto your website gradually).

JPEG. Joint Photographic Experts Group compressed file. Compressed image file used on the internet. JPEG supports 24-bit and 32-bit color depth and so is good to use when you have a color photograph. However, JPEG is not a good idea when you have line art or other images with large blocks of solid color; your image will look messed up. Also, JPEG compression is "lossy," meaning that it discards some information to make the files smaller. Although you can control how much is discarded on saving, it's best to save your original scans as TIFFs or some other "lossloss" file type (i.e. one that doesn't discard data).

PICT. Macintoch-specific image format. Don't use for print or web.

TIFF. Tag Image File Format. The standard file format for printing photographs. It's cross-platform and importable into virtually all desktop publishing (DTP) and image manipulation programs, but since there are so many extensions used in creating and manipulating tiffs, using them can be tricky.