A few people are sitting inside of a building with lots of photography on the walls.
The people are viewing a new art exhibit.
Not all art is photography, some restaurants have photography on the walls New is not implied in the first sentence, it gives information unavailable previously An exhibit is different than a museum, and implies more information about why the wall has photography on it
Photography can be on walls and not be part of an art exhibit.
Just because in a building with lots of photography on the walls does not mean it is a art exhibit.