Maybe an image is worth a thousand words, as the adage has it. Whether or not this is true, images can add a lot to a paper or presentation, making your ideas stand out. This guide will introduce you to sources for locating images for your projects, some considerations regarding image resolution, and some guidelines for asking for permissions from and giving credit to the creators and/or copyright holders of the images you use in your work.
File types and resolutions
Adapted from David Shipley and Will Schwalbe, eds. Send: The Essential Guide to Email for Office and Home (New York: Knopf, 2007) p. 89-91, and from the JISC Digital Media Guide "Choosing a File Format for Digital Still Images":
- .pdf -- Best for text documents -- abbreviates white in the computer's memory to save space
- .jpg -- Best for compressing high-resolution images -- reduces file size by stripping some information
- .gif -- Mainly used for photographs -- only supports 256 colors -- Most useful for figures and diagrams with only a few colors, but losing popularity as a format
- .png -- Useful for medium-grade resolution -- .gif-like compression, but no limit to the colors it can support
- .tiff -- Does not discard information from the file -- useful for high-resolution images
TIFF is the preferred file format for saving captured images at the highest quality level. You can choose a less robust file format to save memory when needed, but if you originally save a file in a low-resolution format, you will not be able to take it to a higher resolution later.
Preferred File Formats for Particular Uses:
Commercial printing: TIFF (RGB), TIFF (CMYK), EPS, PDF
Desktop printing: TIFF (RGB), PSD, JPEG (at high quality setting)
Web use: JPEG, GIF, PNG
72 pixels per inch (ppi): Ideal resolution for an image to be displayed on a computer
300 ppi: Ideal resolution for an image to be printed (professional quality)
To determine how large an image can be in a digital or print format:
1. Determine the pixel size of an image
2. Divide that by the ppi appropriate for your purpose
3. The result is the ideal measurement in inches for the display of your image.
Another option in addition to those below is to purchase stock photos. Sites like iStock, Fotolia, Shutterstock, Corbis, and Getty Images sell these for various costs and purposes. Many museums will also allow you to take your own photographs if they are for personal use.
See the "Specific Image Resources" page for links to denominational image resources.
Image resources around the web
Head of Public Services and Periodicals Librarian
Periodicals Room, Pitts Theology Library