Always enter into photo agreements in writing. The contract should contain clear provisions on your rights and obligations as the buyer of the photos.
All rights of use (if possible, exclusive ones) should rest with Freie Universität Berlin without any limitations in terms of time or physical area. In general, it is a good idea to secure the right to use the materials in connection with reporting on Freie Universität (print and online) as well. This allows you to provide the photos to third parties (media) even years later – citing the appropriate source, of course.
Those who acquire exclusive rights of use generally pay a little more, but save time, money, and effort in the long run. In the case of a non-exclusive right of use, you may have to pay again for an image that you had made for a certain brochure, or you may be barred from using it online and have to have new pictures taken.
Arrange in advance with the photographer the desired credit line (copyright) and the rights of use (factual rights and those related to time and territory).