Even though the game controls say to hold down the touchpad on the PS4 controller to enter photo mode, nothing happens. Kinda annoying when a feature offered on the game doesn't work as advertised.
The touchpad is for the route map, not the camera. If you want to take pics then click R3, select external camera and then whichever camera you want. You can then pan around, up and down around the train to whatever angle you like. I prefer free camera as it doesn’t follow the train and stays where you choose.
The control scheme for the game lists holding the touchpad to take an in-game screenshot while in first person. From what I've experienced, it doesn't work.
I'm almost certain this was mentioned in a stream a long while back. Always worth logging a ticket with DTG Support to see what the response is. Considering the PS4 has an in built share function, capable of taking screenshots... I'd imagine it's very close to the bottom of the list.
I think the developers got confused when making these diagrams. For example, the game still says to press Share to open the map!