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.
Types of Image Use
Educational Use -- Educational uses permit the most latitude with what's considered "fair use" but considerations do include whether or not you are posting material online, the type of resource used, and the purpose for which an item is used. See the "Fair Use Checklist" from Columbia to help your assesment.
Religious Use -- In the context of religious uses, the most latitude is given to uses of copyrighted materials during worship services. However, these rights do not extend to words presented on a screen, book excerpts produced in a bulletin, or any activities that occur outside of a worship service. For those purposes, permissions must be sought and payment may be required. The Unitarian Universalist Association presents a nice summary of "Copyright Issues Related to Worship".
Online Use (Blogs, Newsletters, Web Sites, etc.) -- It is not acceptable to pick an image from Google Images and paste it on a personal blog, a website, or any other digital space without first checking permissions and receiving permissions where such must be sought. People do get sued for using others' images without permission, and it does not matter if you link to the original source, attribute the author, etc., if the use is not considered "fair." The best strategy is to use either images you create or can determine use permissions for via a Creative Commons license or by being in the public domain. Some stock photo sites, like Getty, have recently made it legal for bloggers, websites, and social media users to embed certain images from their collections; in exchange, Getty receives some information about the traffic to your site.
Commercial Use -- For a commercial use, plan to seek permissions and be prepared to pay a use fee for anything that is not in the public domain.