Zograscopic viewing

The “zograscope” is a “visual aid” (commonly known as “optical machine” in the 18th century) invented in the mid-18th century, and in general use until the early 20th century. It was intended to view single pictures (thus not stereographic pairs) with both eyes. The optics approximately eliminates the physiological cues (binocular disparity,...

Interaction of depth probes and style of depiction

We study the effect of stylistic differences on the nature of pictorial spaces as they appear to an observer when looking into a picture. Four pictures chosen from diverse styles of depiction were studied by 2 different methods. Each method addresses pictorial depth but draws on a different bouquet of depth cues. We find that the depth...

Gauge fields in pictorial space

“Pictorial space” is the mental structure that appears to be the scaffold for the visual awareness when looking “into” (as opposed to “at”) a picture. Its structure differs from the “visual space” that is the scaffold for the visual awareness when looking into the scene in front of the observer. The structure of pictorial space has been probed...

Space-time disarray and visual awareness

Local space-time scrambling of optical data leads to violent jerks and dislocations. On masking these, visual awareness of the scene becomes cohesive, with dislocations discounted as amodally occluding foreground. Such cohesive space-time of awareness is technically illusory because ground truth is jumbled whereas awareness is coherent....

Blow-up: A free lunch?

We consider operations that change the size of images, either shrinks or blow-ups. Image processing offers numerous possibilities, put at everyone’s disposal with such computer programs as Adobe Photoshop. We consider a different class of operations, aimed at immediate visual awareness, rather than pixel arrays. We demonstrate cases of blow-ups...

Awareness of the light field: The case of deformation

Human observers group local shading patterns into global super-patterns that appear to be illuminated in some unitary fashion. Many years ago, this was noticed for the case of uniform, unidirectional illumination. Recently, we found that it also applies to convergent and divergent illumination flows, but that human observers are blind to...

Shading, a view from inside

Shape from shading arose from artistic practice, and later experimental psychology, but its formal structure has only been established recently by computer vision. Some of its algorithms have led to useful applications. Psychology has reversely borrowed these formalisms in attempts to come to grips with shading as a depth cue. Results have been...

Measuring 3D point configurations in pictorial space

We propose a novel method to probe the depth structure of the pictorial space evoked by paintings. The method involves an exocentric pointing paradigm that allows one to find the slope of the geodesic connection between any pair of points in pictorial space. Since the locations of the points in the picture plane are known, this immediately...

Light fields and shape from shading

From a theoretical point of view, the use of the shading cue involves estimates of the light field and thus observers need to judge the light field and the shape simultaneously. The conventional stimulus in perceptual experiments, a circular disk filled with a monotonic gradient on a uniform surround, represents a local shading or tonal gradient...

Illuminance Flow Estimation by Regression

We investigate the estimation of illuminance flow using Histograms of Oriented Gradient features (HOGs). In a regression setting, we found for both ridge regression and support vector machines, that the optimal solution shows close resemblance to the gradient based structure tensor (also known as the second moment matrix). Theoretical results...

Structure of light fields in natural scenes

Light fields [J. Math. Phys. 18, 51 (1936) ;The Photic Field (MIT, 1981)] of natural scenes are highly complex and vary within a scene from point to point. However, in many applications complex lighting can be successfully replaced by its low-order approximation [J. Opt. Soc. Am. A 18, 2448 (2001); Appl. Opt. 46, 7308 (2007)]. The purpose of...

Haptic perception disambiguates visual perception of 3D shape

We studied the influence of haptics on visual perception of three-dimensional shape. Observers were shown pictures of an oblate spheroid in two different orientations. A gauge-figure task was used to measure their perception of the global shape. In the first two sessions only vision was used. The results showed that observers made large errors...

Representing the light field in finite three-dimensional spaces from sparse discrete samples

We present a method for measurement and reconstruction of light fields in finite spaces. Using a custom-made device called a plenopter, we can measure spatially and directionally varying radiance distribution functions from a real-world scene up to their second-order spherical harmonics approximations. Interpolating between measurement points,...