First of all, I am not a lawyer. Now that I have completely disqualified myself, and warned you that any information given hereafter may or may not be true in a given country at a given time for given people in given settings for given tasks, I can now broach the subject.
The other day I was looking at a medical clipart site which contained ancient black and white clipart images which had obviously fallen out of the copyright realm and were in the public domain – IT WAS NOT. Why? The people who had scanned the black and white pictures from ancient manuals in the public domain, considered that the work of scanning, cleaning the drawing (removing the aged paper color to make it white again), cropping the final art and giving it the clipart resolution was considered DERIVATIVE WORKS of a public domain image. In other words, if your aim is education, feel free to use it, but if you use it for a commercial presentation – find the book at your national library and scan it yourself :).
And now for another surprise. You visit an art gallery where a 1789 painting (surely no copyright issue here, right?) attracts your attention and you take a high resolution photo which you use on your slide and distribute or make available to others. Understand that the law in the US and in the UK is different. In the US, you could do that without problem. In the UK, the art gallery could make trouble for you unless you only use a low resolution image.
In this blog I use images that are under CC licence (Creative Commons). If you are not familiar with Creative Commons, STOP whatever you are doing and visit http://search.creativecommons.org/# From that page, you have access to the images that you can reuse under very well defined conditions. For example, I selected the button “Use for commercial purposes”, and deselected the button “modify, adapt or build upon”, clicked on the button “Flickr”, selected “the Commons” in the menu on the left of the search line and then typed “eye” in the search window. I found a great image named “Elod-Eye” by Frederic Dupont (a.k.a darkpatator). Then scrowling down the page, at the bottom right, I found the license type, in this case “Some rights reserved”. Clicking on the licence name in grey takes you to the page Some rights reserved which explains what are these rights. You can then use that picture on your slide according to the stated rights.Here are several sites where you can find public domain images: http://wellcomeimages.org and also the images of the British Library https://www.flickr.com/photos/britishlibrary/sets/ and of course the huge Flickr internet archive book images
There are other issues of course. The first one is the display of recognizable people on an image. Each one of us has “personality rights“, which include the right to control the commercial ( and even non commercial) use of our image and likeness. They vary from country to country, and from State to State. So even if you yourself took the photo, as long as it contains a recognizable person, before using that photo for a presentation, it would be wise to make sure that this person has given you permission to use that photo in a presentation (there are release forms available online that you can base your form on).
Now for the case where your slide features diagrams from other published papers (say as background information), or images from a webpage, should you mention the source of the diagram or of the web-image on your slide under the image or diagram? ABSOLUTELY. If it is from a scientific journal, you could write the last name of the author and initials, the year of publication, and the abbreviated journal name, in readable font size. If it is from a website, the URL of the site. You would not want to be accused of plagiarism in a public forum, now would you?
By Jean-luc lebrun