A 60-ish man wearing a yellow vest bearing the name of some charity stood on the sidewalk outside the Oak Park Starbucks and gestured with a donation can to the dozens of passersby. For ten minutes no one contributed.

A young woman shouldering a padded camera bag approached and struck up a brief conversation. The man nodded in apparent agreement and she began scribbling onto a small journalist’s pad, then knelt by the curb across the sidewalk from him, focusing her camera.

Then something fascinating happened:

A passing woman spied the yellow vest and looked away–straight into the camera. This caused her to pause. She reached into her purse and walked back to the man. She glanced at the photographer, oriented her posture for maximum exposure to the lens, smiled, and donated.

A second later a man in a business suit exited Starbucks. He passed by the can, walking toward the street–and noticed the photographer. He spun around, returned to the man, balanced his briefcase and hot coffee in one hand, and dropped some change into the can, angling his face subtly toward the photographer.

Few now passed without donating. A queue formed of people waiting to contribute.