Images can be powerful teaching tools, as illustrations to in-class lectures, or for studying concepts outside of the classroom.
In-class display is usually okay!
Most of the time, showing things to students in class at the University of Minnesota is totally okay - there is a specific provision in the law that allows teachers to display copyrightable materials for students, without limitation, in non-profit, face-to-face, classroom settings. (If not for this exception, showing things in a classroom would be a public display that might require payment and/or permission.)
It's not a flexible exception, like fair use - it only applies to teachers, and only in specific situations. But it also is not at all uncertain - you don't have to guess at market harm issues, or how much is an appropriately small amount. Learn more about the Classroom Use Exemption.
- Holding up illustrations from a book, or passing books, prints, maps, or other hard-copy images around a classroom
- Using a traditional overhead projector, slide projector, or a document projector to display images
Note: online and distance classes are not covered by the Classroom Use Exemption - it only applies when students and teachers are physically present in the same space. You may well be able to display things for your students, but you'll have to think about it in terms of fair use.
Instructional/educational display outside of the classroom
Sometimes uses that feel very similar to the user are treated differently by the law - for example, showing an image in a non-profit face-to-face classroom may be permitted by the Classroom Use Exemption, but showing the same image, in a very similar instructional setting that is not technically a class is not so clearly allowed. So display of images in online instruction, at conferences, in school meetings, etc - may be allowed, but you have to think about fair use.
Copying or scanning images for instructional use
The Classroom Exemption, mentioned above, doesn't cover -making copies- at all; it says you can show a picture from a book, but it does not say that you can scan the picture out of the book in order to put it in a presentation file that you project from your computer. You may be able to copy the pictures from the book in order to use them in class, but if so, it will be because of fair use - which is less clear than the Classroom Use Exemption.
Fair use almost certainly covers some copying of images for instruction, especially in the non-profit context. It's also likely that not all image copying, even in non-profit instructional contexts, falls under fair use. Courts haven't done much to interpret how fair use might apply to instructional use of images, but they have allowed fair use copying of images in other contexts - sometimes even commercial ones - especially when accompanied by criticism or commentary. You can learn more about general principles of fair use, or if you're already familiar with the principles, think through your specific use.
If making the copies is a legitimate fair use, then subsequently showing them in class is probably permitted under the Classroom Use Exemption. However, the Classroom Use Exemption does not apply to copies that are not legitimately obtained.
Posting images online for student use
Sharing images online with students, whether embedded in a presentation file (if you distribute Powerpoint files, for example), or as stand-alone images in a course website, is also usually a question of fair use.
The Visual Resources Association has produced a very useful "Statement on the Fair Use of Images for Teaching, Research, and Study". The statement articulates the organization's understanding of fair use principles, but it's not legal advice. It's a bit longer than this website, but very much worth the read for anyone whose teaching is image-heavy.