Reproductions and Digital Camera Use policies are different at each institution.
Reproductions in Special Collections at Princeton University Library
Digital Camera Use in Special Collections at Princeton University Library
Make sure to take pictures of the box, folder, and other relevant metadata to keep track of where you took the image and of what you'll need to cite its location.
Copyright and Permissions
Knowledge of your research items' copyright and permissions to reproduce images of them in publications will affect what and how you can publish. Make sure to note what permissions are necessary to do so and what kind of copyright your resources might have.