For me, one of the most valuable concepts in street photography is the ten-foot shot. Weegee mentions this in his writings. In his case, ten feet was useful for a full-length photo at a known f/stop when using flash. And he, along with most press photographers used flashbulbs for shooting during both night and day. They would walk around with their Speed Graphics racked to 10 feet and their lens set to the correct stop, and their shutters cocked.