A long-held belief about why people in old photos aren’t smiling is that the exposure times were simply too long for a person to maintain a smiling pose. For example, one of the first photographs ever taken by Louis Daguerre in 1838 of a busy street probably took between 10 and 15 minutes of exposure time. The people, horses, and carts that lined the streets and sidewalks? They’re not visible in the photo at all, showing what a blurred mess a photograph could be if there was movement.

But, according to Voxfilmmaker Phil Edwards, advances in photography in the 1800s meant that exposure time was not the only reason why folks didn’t smile in photos. We’re often told that the Victorians were very stern and taught not to smile, but that’s not exactly true either. Discover another explanation for all the somber faces in the video below. And, be sure to check some smiling Victorians caught unaware by clicking “Next Page” after the video.