A test of what is a normal lens then, is to find one that renders a printed (or otherwise displayed) photograph of a scene that when held at 'normal' viewing distance (usually arm's length) in front of the original scene and viewed with one eye, matches the real-world and the rendered perspective, though Maurice Pirenne (in 1970) and others demonstrate that it is possible to see a scene made with any lens in normal perspective if one adjusts the viewing distance; but impractically close to the image for wide angle photographs and further away for a telephoto, and views it from a static point at the centre of perspective from which the image was made, supporting the observations of perspective paintings made by Leonardo da Vinci.