Exercise 2.4 The Portrait
Here is a more standard choice of focal length and perspective for a portrait shot using a background some distance behind the subject and a reasonably wide aperture, taking into consideration the distance of the subject from the background. The shot was taken approximately 1.5metres from the subject focussing on the eyes and looking for some expression.
The image was taken at a 100mm focal length giving the necessary compression for a headshot. In a exercise 2.2 it was stated that a 50mm focal length approximates the perspective distortion of human vision and whilst this is true it is usually necessary to compress the angle of view, more than a 50mm focal length will compress, when taking a headshot as to take a headshot with a 50mm focal length would require a photographer to minimise the distance between themselves and their subject therefore reintroducing perspective distortion.
The longer focal length has effectively taken us further into a scene, effectively zooming in from our natural human perspective. This allows us to have effectively compressed space, which means that when we use a longer focal length with a wider aperture the effect on the depth of field is more significant than when we use a shorter focal length with that exact same aperture.