url: http://docs.mongodb.org/manual/tutorial/project-fields-from-query-results/

in "Projection for Array Fields," it has the text: "The $elemMatch and $slice projection operators are the only way to project portions of an array."

This is not true; you can use dot notation. Run the following in the shell:

db.foo.insert( { a : [5, 6, 7, 8], b : [ 11, 12, 13, 14] } )
db.foo.find( { "a.2": 7 }, { _id : 0 , "a.$": 1 } )