"Think about cameras, lenses, and the difference between film and sensors."
Sticherbeast talks about the changes in photographic technology that make a photo from the Sixties look like a photo from the Sixties.
Also note how this photograph doesn't perfectly look like reality. Much of this comes from the fact that it was shot with grainy high-speed film, with unrealistic tones which we already contextually relate to a previous era. It looks like a photo from the 60s, because the technology wasn't there to make the shot look realistic.