You can adjust the dioptres of the viewfinder with a little scrollwheel next to it, to match your personal eyesight. Farsighted people will then be able to look through the viewfinder without wearing their glasses or contact lenses and see a sharp image. They will see the same sharp image as a person with perfect vision would see looking through it with the dioptre setting at 0. Then the photographer can use the manual focus to take a picture that looks sharp to them (with adjusted dioptre-setting) and it will also be a sharp photo ‘to the camera’.