How to crop portrait pictures

Portrait pictures always come in different sizes, different background colors, different poses. Ideally, you would make one consistent photo shot. The next best alternative is fixing things using the crop function. If it not possible to resize/crop the pictures in such a way that faces have the exact same proportion, hold on to these guide lines:
  • Eye lines at the same hight
  • Eye lines close to the "golden proportion" of 62%