Did early Renaissance painters trace optical projections? Evidence pro and con

摘要

Recently it has been theorized that some European painters as early as 1420 used concave mirrors (and, later, converging lenses) to project real inverted images onto their supports which they then traced and painted over. We review the image analytic, historical and art historical evidence and counter-evidence for this bold claim, focusing on key paintings in the debate. While some of the evidence is consistent with the use of optical projections in the 15th century, all such evidence is also consistent with other explanations as well. More importantly, for those paintings highlighted as supporting the projection theory, there is much evidence that is inconsistent with the use of optics or extremely difficult to explain as arising from the use of optics. Further, there is no historical documentary evidence from the 15th century suggesting anyone had even seen an image of an illuminated object projected onto a screen―the first step in the proposed projection method. The projection method would have been the most sophisticated optical procedure of its day, which theory proponents speculate was discovered by artists, not the scientists who were actively exploring optical systems. Because the burden of proof lies foursquare upon the theory's' proponents―the revisionists―in the absence of compelling reasons to reject "traditional" (non-optical) explanations we must reject the projection theory. We conclude by rejecting the claims that the optical projection theory has been "proven."