The distance to hold the photograph

Holding the photograph at the proper distance away from the eye is very important, or otherwise we get the wrong perspective. How far away should we hold a photograph? To recreate the proper picture we must look at the photograph from the same angle of vision from which the camera lens reproduced the image on the ground glass screen, or in the same way as the object being photographed. Consequently, we must hold the photograph at a distance from the eye that would be as many times less than the distance between the object and the lens as the size of the image on the photograph is less than its actual size. In other words, we must hold the photograph at a distance which is roughly the same as the focal length of the camera lens. A photograph tacked on a wall also seems flat because it is looked at from a still greater distance away. Only the short-sighted with their short focal length of vision, as well as people, who are able to accommodate their vision to see objects very close up, will be able to admire the effect that an ordinary photograph produces when we look at it properly with one eye, because when they hold a photograph 12-15 cm away, they get not a flat image but one in relief the kind of image a stereoscope produces.