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Proceedings Paper

Optical or mechanical aids to drawing in the early Renaissance? A geometric analysis of the trellis work in Robert Campin's Merode Altarpiece
Author(s): Ashutosh Kulkarni; David G. Stork
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Paper Abstract

A recent theory claims that some Renaissance artists, as early as 1425, secretly traced optically projected images during the execution of some passages in some of their works, nearly a quarter millennium before historians of art and of optics have secure evidence anyone recorded an image this way. Key evidence adduced by the theory's proponents includes the trelliswork in the right panel of Robert Campin's Merode altarpiece triptych (c. 1425-28). If their claim were verified for this work, such a discovery would be extremely important to the history of art and of image making more generally: the Altarpiece would be the earliest surviving image believed to record the projected image of an illuminated object, the first step towards photography, over 400 years later. The projection theory proponents point to teeny "kinks" in the depicted slats of one orientation in the Altarpiece as evidence that Campin refocussed a projector twice and traced images of physically straight slats in his studio. However, the proponents rotated the digital images of each slat individually, rather than the full trelliswork as a whole, and thereby disrupted the relative alignment between the images of the kinks and thus confounded their analysis. We found that when properly rotated, the kinks line up nearly perfectly and are consistent with Campin using a subtly kinked straightedge repeatedly, once for each of the slats. Moreover, the proponents did not report any analysis of the other set of slats-the ones nearly perpendicular to the first set. These perpendicular slats are straight across the break line of the first set-an unlikely scenario in the optical explanation. Finally, whereas it would have been difficult for Campin to draw the middle portions of the slats perfectly straight by tracing a projected image, it would have been trivially simple had he used a straightedge. Our results and the lack of any contemporaneous documentary evidence for the projection technique imply that Campin used a simple mechanical aid-such as a minutely kinked straightedge or a mahl stick commonly used in the early Renaissance-rather than a very complex optical projector and procedure, undocumented from that time.

Paper Details

Date Published: 2 February 2009
PDF: 9 pages
Proc. SPIE 7251, Image Processing: Machine Vision Applications II, 72510R (2 February 2009); doi: 10.1117/12.806247
Show Author Affiliations
Ashutosh Kulkarni, Stanford Univ. (United States)
David G. Stork, Ricoh Innovations, Inc. (United States)
Stanford Univ. (United States)

Published in SPIE Proceedings Vol. 7251:
Image Processing: Machine Vision Applications II
Kurt S. Niel; David Fofi, Editor(s)

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