Using Pictures
Pictures are similarly to texts also protected by copyright law. Therefore, you need permission to use them.
The copyright holder might have given permission in advance for the free use of a picture either by acknowledging this or by using a Creative Commons license. Read more about Creative Commons.
If the photographer died more than 70 years ago, the picture is no longer protected by copyright, and you can freely use it - if you give the photographer’s name alongside it.
Pictures should in this context be understood broadly as visual art, drawings, photos, illustrations, graphs and figures.
Pictures in papers
If you use pictures in connection with your studies, you are as a student covered by the agreement between The University of Copenhagen and VISDA (formerly Copydan Billedkunst).
Within this agreement you are allowed to find a picture on the internet and use it in a paper or a PowerPoint, as long as the material is only accessible from a closed and secured system such as Absalon or KUnet, and it is not published anywhere else.
Pictures in papers you publish
If you upload a paper to a student paper repository, on social media, on your website or similar places, and therefore making the paper publically available, you will no longer be covered by the agreement between the University of Copenhagen and VISDA (formerly Copydan Billedkunst).
In this case you have to either remove the pictures from the paper, contact the copyright holders and ask for their permission to use the pictures or find pictures under a Creative Commons license.
Always remember to reference the source, regardless of using the picture in a paper, a PowerPoint etc.
Using your own pictures
If you use a picture in your paper that you have taken yourself, you still have to remember to get permission to use it from the people that might appear on the picture. It is always best to get the permission on paper.