Pictorial cues

David SP, Munafo MR, Johansen-Berg H, Smith SM, Rogers RD, Matthews PM, et al (2005) Ventral striatum/nucleus accumbens activation to smoking-related pictorial cues in smokers and nonsmokers a functional magnetic resonance imaging study. Biol Psychiatry 58(6) 488 94... 

In addition to the phenomenological sense of looks, there is also what is often called its epistemic sense. When we say that an item looks small to an observer, using looks small in this second sense, we mean that the observer s current visual experience provides adequate evidential support for the belief that the object is small. When we have this second sense in mind, we would not be willing to say that a car looks small to an observer if the car is at an appreciable distance from the observer, for when a car is at an appreciable distance from an observer, the observer s visual experience presents pictorial cues that are indicative of distance. Thus, for example, when an object stands at some distance from an observer, the features of the object seem indistinct. In a case of this sort, the observer s experience supports the belief that he/she is seeing a car of normal size, but a car that is... 

The second category of pictorial cues is strongly coupled to the perceived spatial frequency (texture density gradient, blur from defocus) and color/luminance (atmospheric haze, shading). Therefore, these cues are directly processed on a low neuronal level in the HVS (see Sect. 3). 

Held et al. has confirmed this theory by developing a probabilistic model of how viewers may use defocus blur in conjunction with other pictorial cues to estimate absolute distances to objects in a scene [5], which has been validated with a perceptual study. Their findings indicate that blur is not only an ordinal but absolute depth cue if it is presented in conjunction with other monocular cues. 

Seddon, G. M., Eniaiyeju, P. A. (1986). The understanding of pictorial depth cues, and the ability to visualise the rotation of three-dimensional structures in diagrams. Research in Science and Technological Education, 4( ), 29-37. 

The reason for strong depth and distance perception despite missing or limited stereo cues is the capability of the HVS to process additional pictorial as well as dynamic monocular depth cues, which are embedded in the 2D projection of the sensed scene. Dynamic cues arise from apparent motion of the visible objects or ego-motion (motion parallax) as well as the orientation of the eyes (vergence) or focused distance (accommodation). Dynamic cues will not be considered in detail since they do not suit to be manipulated within still images or video sequences to... 

Flannagan, M.J., Sivak, M., Simpson, J.K. The relative importance of pictorial and nonpictorial distance cues for driver vision. In Proceedings of the International Driving... 

To convey distance information via pictorial depth cues, depth maps have to be generated first. Therefore stereo camera based algorithms which implement dense depth map reconstruction methods (e.g. Semi Global Matching [2]) may be utilized. 

The human visual system extracts depth information from various physical effects which manifest as pictorial depth cues. One of these effects is atmospheric haze which has been discussed in Sect. 7.2 of chapter Human Visual Perception . Furthermore, the findings of Troscianko et al. [37] indicate that depth encoded in color (de-)saturation influences human depth perception in general. These results point towards a subconscious interpretation of relative color saturation in the viewed image. This effect is associated with the weak ordinal depth cues which support the assessment of scene layering and foreground/background separation process (see Sect. 5.2 of chapter Human Visual Perception ). 

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