Video: Why People Don’t Smile in Old Photographs
Vox published a 3-minute video, Why People Never Smile in Old Photos, which features different explanations of this phenomenon.
Among the main reasons the authors of the video mention is long exposure time in early cameras: in order to get a good picture, people had to sit still for several minutes, and many could not continue smiling for this long.
Other possible explanations include the heavy influence painting had on early photography and the fact that smiling was looked down upon at the time. It is mentioned that in the early 20th century people thought that “smiling was for idiots”.