Alan Adler on the notion that the Shroud image is a photograph
The late Alan D. Adler, Emeritus Professor of Chemistry at Western Connecticut University, in an article, “The Nature of the Body Images on the Shroud of Turin,” commenting on those who propose that the image on the Shroud was a medieval proto-photograph created by Leonardo da Vinci:
[they] propose a photochemical mechanism with sunlight reflected from a statue via optics to image on sheet of cloth charged with a mixture of egg white and chromium salts. As this is an albedo image, it will fail a VP-8 test and there is no chemical or spectroscopic evidence for their chemical sensitizers. They do not deal with the blood image problem [“exudates from clotted wounds transferred to the cloth by its being in contact with a wounded human male body”]. Leonardo may rest easily in his grave.