You need to look at it from the perspective of the system. The system has a database of individuals and is asked "does this photo matches any of the individuals

You need to look at it from the perspective of the system. The system has a database of individuals and is asked "does this photo matches any of the individuals in your database?" If someone whose photo is basically a dark circle with eyes is entered in the system then the next time you ask the system to identify a photo that is basically a dark circle with eyes the system will respond to with the previous match. Like a bloom filter with a bitvector of size 1.