"The doctrine of fair use has developed through a substantial number of court decisions over the years and has been codified in section 107 of the copyright law." -from www.copyright.gove/fls/fl102.html
The "Four Factors of Fair Use" are:
Fair use is not easily defined, even with these factors outlined, so one must consider each use of an image individually, uniquely. Acknowledging the source of a copyrighted work does not substitute for obtaining permission to use it. Generally under "fair use" there are a few guidelines that scholars and students can live by when dealing with images for classroom presentations and assignments (excluding all published work). Please see our page on Digital Images and Copyright for an outline of these guidelines.
- The purpose and character of the use, including whether such use if of commercial nature or is for nonprofit educational purposes
- The nature of the copyrighted work
- The amount and substantiality of the portion used in relation to the copyrighted work as a whole
- The effect of the use upon the potential market for, or value of, the copyrighted work