| | Art and Optics : David G. Stork: Focal lengths |
 | | Using standard techniques based on assumptions of the size of Arnolfini, his wife, the distance to the rear wall, and measurements of their sizes of the images shown in the famous convex mirror depicted within the painting, I estimated the focal length of that convex mirror to be about 12 cm. |
 | | In any case, polishing a mirror the size of that depicted in the Arnolfini portrait would have been an astounding challenge, nearly a quarter millennium before the invention of reflecting telescopes by James Gregory in 1663. |
 | | In short, the evidence given by the image reflected by the convex mirror depicted in the Arnolfini portrait does not support the use of a concave mirror in the rendering of the painting without some ad-hoc and arbitrary claims (such as the mirror was visible, but van Eyck decided not to paint it). |
| webexhibits.org /hockneyoptics/post/stork5.html (1380 words) |