In the Mausoleum of Galla Placidia (Ravenna, Italy), the San Lorenzo lunette
shows two peculiar visual effects: a transparency effect of gold seen through
gold and perceptual collinearity between two parts of a cross which are
physically misaligned. Both effects are found within the area of the halo
surrounding the saint's head. In this work we addressed the problem posed by the
physical misalignment of the cross. Our hypothesis is that the physical
misalignment went unnoticed throughout history because the artist produced a
perceptual alignment to correct for the Poggendorff illusion. Hence, we asked
observers to align two ends of a cross in a reproduction showing the silhouette
of San Lorenzo's torso holding the cross. Results support our hypothesis: both
direction and magnitude of adjustments comply with the alignment in the original
mosaic.
KoningAvan
LierR,
2007“3-D processing in the Poggendorff illusion”Acta Psychologica12646–58
2.
RicciC,
1914“Il sepolcro di Galla Placidia in Ravenna. Parte
IV”Bollettina d'Arte del Ministero della Pubblica Istruzione8141–174
3.
TopperD
R, 1984“The Poggendorff illusion in Descent from the Cross by
Rubens”Perception13655–658 doi:10.1068/p130655
4.
VicarioG
B, 2008“Optical-Geometrical Illusions: The Nomenclature”Gestalt Theory30168–180
5.
ZavagnoD,
1996“L'effetto trasparenza nella Lunetta di san Lorenzo nel Mausoleo
di Galla Placidia in Ravenna”Effetto Trasparenza Eds BortolattoLda
PosO pp
18–22 (Treviso,
Italy:
Stampa)
6.
ZöllnerF,
1860“Ueber eine neue Art von Pseudoskopie und ihre Beziehungen zu den
von Plateau und Oppel beschriebenen Bewegungsphänomenen”Annalen der Physik und Chemie186500–523
doi:10.1002/andp.18601860712
