Approved File Formats
Some formats are better for different data and presentation. If your image needs to be printed, go for a format that produces a larger file size. For example, images that are only intended to be viewed on screen, a resolution of 72 or 75 dpi will result in a small file that can be easily downloaded. A resolution of 300-600 dpi is recommended for images that are intended to be printed.
- PDF (.pdf) - good for line drawings with searchable text, e.g., maps.
PDF is best used to store vector-based graphics (i.e., graphics drawn using lines and curves rather than pixels). Vector graphics stored in PDF format will be much smaller, will read more cleanly, and any included text will be searchable. Equations, charts, and diagrams that combine text with vector-graphics are particularly appropriate to store in PDF format.
- JPEG (.jpg) - better for photographs
The JPEG format is primarily used to store photographs. JPEG is a "lossy" format, meaning that some image quality is sacrificed in order to produce much smaller files. Images of higher quality should be stored in TIFF format instead (see below). Non-photographic images such as graphs and charts will be smaller if stored in GIF format instead (see below).
- GIF (.gif) - better for images other than photos, e.g., drawings.
The GIF format, developed by CompuServe, is best used to store screen-quality images that do not contain many colors. GIF files are typically very small, but cannot reproduce the range of colors necessary to reproduce photographic images (use the JPEG format instead -- see above).
- TIFF (.tiff) - for archival images these files are the largest. More info is stored.
The TIFF format is an archival format, meaning that it does not sacrifice image quality in order to reduce file sizes. TIFF images are excellent for storing detailed, high quality images. However, TIFF files tend to be much larger than either JPEG or GIF images, and cannot be opened using most web browsers without installing and configuring additional viewing software or plug-ins.
- PNG (.png) - created to replace gif format and is acceptable for photos
The PNG format is an open standard developed to replace the Compuserve GIF format. Like GIF files, low-color images stored in PNG format are typically quite small. Unlike the GIF format, the PNG format can also be used to store high-color images, which means it is also suitable for storing photographic content.
- MPEG (.mpg) The MPEG format is the oldest and most widely supported format for movies. There is a wide range of viewers available for all platforms. The MPEG format is commonly used as an output format from UNIX utilities that generate video content.
- QuickTime (.mov, .qt) The QuickTime format was originally more of a Macintosh-specific format. These days, support for QuickTime movies is good on both the Macintosh and Windows, but not as good on UNIX.
- Audio Video Interleaved (.avi) The AVI format is more of a Windows-specific format used by Microsoft, and is not as well supported on other platforms. AVI supports both audio and video.
Suggestions Regarding Video Content
Video is one of the most resource-intensive types of multimedia. Unfortunately, video content that is even half of broadcast quality is often too large to download from home. Consider including lower quality versions of video content in addition to high quality originals.
- WAV (.wav) The default standard for Windows sound files is also supported by most other platforms.
- AIFF (.aif) The AIFF format is a Macintosh-specific equivalent of the WAV format. It is not as well supported on all platforms as the WAV format.
- MPEG-3 (.mp3) MPEG-3 (or MP3) format eliminates sound data that is not as strongly perceived by the human ear and brain, and, as such, creates files of reasonable quality that are as much as 10 times smaller than the raw data. MP3 files are good for storing long passages of sound content where high quality is not required.
Suggestions Regarding Sound
The quality used to store sound in electronic format reflects the quality of the original recording source. There is very little reason to store low fidelity recordings of speech content in a very high-quality format, as the added file size would not result in any increase in quality. Conversely, high-fidelity recordings should be stored at high-quality.
If you have content that has been created in a proprietary format, it is recommended that you include a copy of the content in both the proprietary format and in a more common format as well. If you have multimedia content that is too large to be downloaded via the web, it is recommended that you include a copy, on CD, of the content stored at the original quality. The use of multimedia other than listed in the Manual must be approved by the Graduate School.
- PPT (.ppt)Microsoft PowerPoint presentations may be included, but should be avoided if possible.