My point is not that social change is a requirement for taking a photograph. Nor is obtaining written consent. The consent distinction I'm making is that the blind man or the unconscious man are incapable of registering the presence of the photographer and exercising consent by removing themselves from the field of view of the photographer or otherwise indicating they do not want to be photographed. When I was in France taking photos, if someone saw my camera and indicated they did not want to be photographed, I did not take their photo. I would not take the photo of someone obviously homeless because in addition to the absence of privacy the homeless person has as a precondition of their homelessness, they may well not be capable of articulating consent because of mental illness and are not aware of what is happening to them.