Shading and shadowing on Canaletto's Piazza San Marco

Whereas the 17th century painter Canaletto was a master in linear perspective of the architectural elements, he seems to have had considerable difficulty with linear perspective of shadows. A common trick to avoid shadow perspective problems is to set the (solar) illumination direction parallel to the projection screen. We investigated in one...

Space perception in pictures

A "picture" is a at object covered with pigments in a certain pattern. Human observers, when looking "into" a picture (photograph, painting, drawing, . . . say) often report to experience a three dimensional "pictorial space." This space is a mental entity, apparently triggered by so called pictorial cues. The latter are sub-structures of color...

Pictorial relief for equiluminant images

Pictorial relief depends strongly on “cues” in the image. For isoluminant renderings some cues are missing, namely all information that is related to luminance contrast (e.g., shading, atmospheric perspective). It has been suggested that spatial discrimination and especially pictorial space suffer badly in isoluminant conditions. We have...