Like any book or journal article, images created by someone else must be cited with a 'sufficient acknowledgment'. This means every time you use an image in an essay you must provide a citation where the image appears and then an entry in your reference list or bibliography. You must also provide a citation to any images you use in presentations, blogs or websites.
It is vital that you keep an accurate record of everything you consult when doing your work and cite what you have used clearly so that:
You can maintain a record of the references you using either a bibliographic software package such as EndNote or by recording the details manually on reference cards.
For more information on quoting and managing references see the i-cite website
To comply with copyright law, even within educational exceptions, you must always include a sufficient acknowledgment when using still and moving images. Think of this like referencing a text - if you did not include the reference you would be plagiarising another person's work.
A sufficient acknowledgement should include the following:
For example: Julia Margaret Cameron, The Mountain Nymph Sweet Liberty, 1866, The Metropolitan Museum of Art
Image databases, like Bridgeman and Artstor, often include an acknowledgement for you to use which can be directly copied and pasted into your work.
When using an image from Flickr or Creative Commons, the name of the person who has uploaded the image can also be used. This is usually included in the details section of the image.