One of the great unwritten rules of photography is that you have to smile when someone is taking your picture. If you don’t, then people will immediately say “Why didn’t you smile? It would look a lot better if you had smiled!”. They will say this even if it is quite clearly not the case, and there are a few pictures of you smiling which prove that.
Some people do not look better smiling on camera. This is a fact which goes against what we want to believe. The idea is that when you smile, you look happy and other people will feel happy looking at the photograph. However, this ignores the fact that people have different shapes of face, and on some people, a smile will look forced and unnatural.
This need not be a bad thing. Ask any modelling agency and they will tell you that the “smoldering” look is far more in demand from clients than smiling shots. As far as most people are concerned, a non-smiling photograph looks more real and more natural. However, many people do not want to think that someone else is in a bad mood or is unhappy to be photographed.
If people tell you to smile more in photographs, be honest with them. Inform them that you don’t leave the smile off because you are in a bad mood, but because you don’t look natural when smiling in photographs. It is not something to be ashamed of – different people suit different looks.