This achievement is earned for finding optional photo #2. If missed on the first run, you can "Play Episodes" and select specific parts of the Episode in order to find the missing optional photos through collectibles mode. The following collectible is described and can be seen below:
] - Optional Photo #2
In the art gallery, go forward, to the right and downstairs. Go up t the girl in the basement area and interact with her camera.
Collecting all 10 photos will also reward you with the following achievement: