Just an observation here folks, as a retired professional portrait photographer. I always found that double the standard focal length was good for head and shoulder portraits and for a tight head shot I would choose a 3x mag. but it does depend on the final size of the image and the viewing distance, as has already been indicated, but also the effect you are trying to achieve. A tight head shot enlarged to say 30"x40" might look good at distance, but closer, well? Times have changed over the years. In the UK, the BBC as I recall, would never shoot a close portrait with a wide angle lens. Not so these days, anything goes. I think they excuse it as reportage and the public have been seduced to it. It does not however, mean it's good photography.