The photo scavenger hunt is one of the discoveries in the game. Similar to the collectibles, you'll have to take a picture of certain landmarks scattered around the map. They'll appear on your minimap when you get close to them, after which they'll show up on your regular map until you complete them. Usually, it's kind of obvious what the landmark is in any given area but if you check the icon on the map it'll tell you what you need to photograph.

You'll get the majority of them when completing districts for All Mine , then there are eight more to find in the desert regions (3 in Rojas North, 1 in Rojas South, 2 each in Badlands North/South). If you need a guide for the ones that haven't shown up on your map through regular gameplay, check the video below by Trophy Tom