Exercise 7: focal length

I've known for years that close-ups present an unattractive, distorted view of a face, but I'd not conducted an experiment like this, moving through the full range of focal lengths available to me.  In looking at these I've learned that the emotional connection we get from a face is impacted by focal length.  The model is not only distant at a long focal length, she looks it. 
My image at 70mm (110mm) seems right; distortion is reduced but the model is still present in the viewer's space.  I suppose I shouldn't be surprised that this is about the old portrait lens standard: 105mm.

18mm on 1.6 factor sensor, (29mm full frame).  The face is very rounded, nose, chin and nearest cheek are oversize, while the other cheek and forehead recede.  A most unattractive view.  Maybe the security folk surrounding politicians and the like are there partly to ensure no one gets this unkind wide angle view.  The camera was very close to the model, invading her personal space.  Another model would have been intimidated by it.

20mm (32mm).  Still a distorted image, the face looks fat, the features out of scale.

35mm (56mm).  A little longer than the old standard prime lens (50mm) but still the face is round, the features distorted.  I might use this if I wanted to emphasise the model's humour - though she'd not think it funny.

43mm (70mm).  This is a usable length; the face looks fairly normal; this is how people look when you're talking to them.

70mm (110mm).  A satisfactory image; the features look natural.  This is how people look when you approach them, and a normal human distance.

96mm (150mm).  This is usable.  The face might be looking a little flat, now, though...

171mm (270mm).  I think the image is definitely flattening now.  It has the distant look that one sees on images of the author on a book's dust jacket.  It's not just the far-away look in her eyes.

250mm (400mm).  Even the model's steady gaze can't retain the connection with the viewer.