There are 20 Photograph locations throughout the four hub worlds. They will show up on the map when you interact with the green map locations. They generally require you to interact with something to either find the tripod or activate it. For example dig it up and build it, or follow a raptor scent trail, or track to find useful objects. Once you do so, select a character with a camera and interact with the tripod. You can only choose from all of your unlocked characters in a hub where you have completed all story mode levels for the associated movie.
The first two characters with a camera are unlocked after the first mission in the second movie. They are Nick Van Owen and Sarah Harding. Other characters with the camera ability are: Sarah Harding (San Diego), Billy Brennan, Ben Hildebrand, Enrique Cardoso, Colin Trevorrow, Steven Spielberg, Gray Mitchell, Gray Mitchell (Survivor), Scott Mitchell, and Tourist Sam.
There is one photo location that is kind of tricky at the Mosasaurus Arena. The tripod is easily visible and already set up, but it requires you to shoot an electric target up in the stands to activate it.