Thanks for your help, I have managed to complete my Essay and hand in on time, with the help of my Girlfriend and advice on here, so thanks again.
Thats the thing about portraits they are bias in a way, they may show a truth about the sitter but not necessarily the whole truth as they will all ways have a bias from the artist, whether that be a photographer or a painter.
Some people may say that that what you see is who the sitter is, I disagree with that, it depends on the context in which the portrait is being made, commercially or in a photojournalistic way, for example a image by Paul Strand of Joseph Goebbels is capturing a certain personality of him which in turn influences peoples opinions of Goebbels, yet an image by Rankin of Tony Blair has an opposite effect he has shot him in a better light to give the viewer a better perception of the Prime Minister for obvious reason(s)
I did also touch upon the Mona Lisa, it is one of if not the most famous portrait ever created. Research has shown that there is great controversy surrounding the painting, some say that it was a self portrait of Da Vinci himself hence the enigmatic smile, others would disagree.
The thirty staff portraits you where employed to shoot must have been a great day, giving you the chance to really compare each photo, like you say some where only there because they had to be where as others where enthusiastic which clearly shows on there facial expressions.
Ian