French photographer Réhahn has been traveling across Vietnam taking pictures of different themes. He has observed that most people hid their smiles once he starts photographing them. Most of them smiles and cover their mouth. Check out why Réhahn calls it his “Hidden Smiles”.
Source: Rehahns Flickr
He presume that this actions might be out of modesty or politeness.
He is currently preparing for an exhibition for those hidden smiles.