last year the american civil liberties unio tested amazon's facial recognition and people were not recognized, primarily people of color. opponents call it an over reach. here toiscuss is surveillance litigation director. and trisha, city hall are porter for the san francisco chronicle. can you explain how it works. how do you go from a camera to having that gytechnol identify you? >> sure. it uses an algorithm to study various aspects of your face and ompare that tooss templets that are already in a data base. an based on the percentage of similarity between your face and the foss ace in the data base, data base will recognize you or not. >> and there are cameras everywhere. so trisha what would san francisco's new ordinance do exactly? >> the first one that supervisor propose is notlow our city ageances to use facial n recognition teogy. it's important to note they don't currently use the technology. and the second aspect of the law that hasn't got as much atention as the outright ban is the -- under this ordinance the -- our sit department will now have to disclose exactly whatnc surveil t