In most portraits and photographs taken before the 1920s or so, the subjects seem to always have a rather stern expression (blank at best). What brought about the standard of smiling for the camera? Changes in cultural attitudes? Not having to pose for long periods of time?
Other than it being a serious and expensive event to be photographed, I always attributed the grave expressions with how long the whole process used to take.
"The phrase "say cheese" appears to have been first used in this way around the 1940s, with one of the earliest references appearing in The Big Spring Herald in 1943:
"Now here’s something worth knowing. It’s a formula for smiling when you have your picture taken. It comes from former Ambassador Joseph E. Davies and is guaranteed to make you look pleasant no matter what you’re thinking. Mr. Davies disclosed the formula while having his own picture taken on the set of his “Mission to Moscow.” It’s simple. Just say “Cheese,” It’s an automatic smile. “I learned that from a politician,” Mr. Davies chuckled. “An astute politician, a very great politician. But, of course, I cannot tell you who he was…”
It is thought the “politician” he was referring to was none other than Franklin D. Roosevelt, who Ambassador Davies served under."