Instructions
Press and hold the left trigger on the Xbox 360 controller to aim Frank's camera. Use the right analog stick to move where the camera is aiming and press "X" to take a picture. Press "A" to zoom out, "B" to zoom in and release the left trigger to put the camera down. A picture only counts if the survivor is clearly shown in the frame.
Take a picture of Carlito on the roof at the very beginning of the game before you enter the mall.
Take a picture of everyone in the entrance plaza. As long as you do not approach the back security gate and trigger the cutscene, you have unlimited time to take pictures. However, once the cutscene occurs, zombies enter the plaza and kill the survivors.
Take a picture of Otis and Jessie in the security room, as well as Natalie and Jeff Meyer on the roof of the mall.
Take a picture of Brad when you meet him in the Food Court. Afterward, Brad appears in the security room along with all saved survivors, in case you do not get his picture when you meet and need to take it later.
Answer Otis when he calls you on the walkie-talkie. Otis directs you to survivors he finds using the mall's security cameras. Take a picture of each survivor Otis directs you to. The remaining survivors for the achievement are all photographed in this manner. When you have taken photographs of 50 unique survivors, the achievement displays at the bottom of the screen.