Amazing Spider-Man (Vol. 1) #262

Story 'Trade Secret'

In Amazing Spider-Man #262, Peter is temporarily distracted and ignores his Spider-Sense. As a result, he gets photographed while changing out of his costume. He spends the story chasing after the photographer, and eventually recovers the film. The photographer is left trying to figure out how to locate a face he saw briefly, from a city of ten million people.

Of course, it always occured to me that if the photographer saw Peter on TV advertising Webs, then he might put two and two together...

This was one of the first Spider-Man comics to use a real photograph for a cover. The other cover I recall was a Marvel Team-Up with Spider-Man and Captain America on the roof of a building. Spider-Woman had quite a few photo-covers.