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LEUKOS - The journal of the Illuminating Engineering Society of North America
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The Journal of the Illuminating Engineering Society of North America: Volume 8 | Number 2 | October 2011

Publisher's data


Editorial:

Lemmings, light, and health revisited


Articles:

A DAYLIGHTING KNOWLEDGE BASE FOR PERFORMANCE-DRIVEN FACADE DESIGN EXPLORATION

JAIME M. L. GAGNE AND MARILYNE ANDERSEN

Heuristics and simple design guides are important tools for designers who wish to incorporate daylighting into the early design process. This paper describes a simulation-based method for generating simple rules for facade design based on specific climate data. A design of experiments methodology is employed to populate a detailed daylighting knowledge base. To enable consideration of both visual performance and visual comfort, the knowledge base contains information about whole-year, climate-based illuminance and glare metrics. Design parameters considered include window and shading device geometry and glazing materials. The approach illustrates how various design elements affect daylighting performance and provides a simple way to approach daylighting early in the design process. It can be employed for design and in educational settings.

THE EFFECT OF SHADOWS ON PERFORMING STEREO VISUAL POINTING TASKS: IS SHADOW-FREE OPEN SURGERY IDEAL?

ARJAN J. KNULST, JESSE VAN DONGEN, MARCO W. M. GROENEWEGEN, ELISABETH D. KAPTEIN, AND JENNY DANKELMAN

Surgical overhead luminaires and head-mounted luminaires are important tools for surgeons. The optical design of these luminaires focuses on providing shadow free light. Shadows, however, are reported as important cues for depth perception in mono- and stereo-visual situations. Because surgeons repeatedly touch delicate tissue with their instruments, their depth-perception should not be hampered. Two experiments were performed to evaluate the influence of shadow on human performance when executing stereo-visual pointing tasks. Experiment 1 studied the effect of the existence of shadows and Experiment 2 studied the effect of the direction of shadows. Subjects were instructed to point random sequences of virtual targets accurately under different shadow situations. Performance was characterized with spatial error E (distance to target, mm). Experiment 1 showed that both large and small high-contrast shadows gave significantly smaller spatial error E (4.8, 4.6 mm, respectively) than either low-contrast shadows (5.6 mm) or no shadows (6.3 mm). Experiment 2 showed that the Error varied (2.1 to 3.2 mm) for different illumination directions. The Error decreased with an increasing angle between the line-of-sight and line-of-light. Illuminating from the center or from the left side of the observer gave better results than from the right side. To maximize depth-perception, surgical luminaires should provide a clear shadow from a light source that illuminates from within the vertical plane through the line-of-sight, and with a 90° angle with respect to the line-of-sight.

TANGIBLE LIGHTING CONTROLS - REPORTING END-USERS’ INTERACTIONS WITH LIGHTING CONTROL INTERFACES

AMARDEEP M. DUGAR, MICHAEL R. DONN, AND WERNER OSTERHAUS

This paper describes a framework to evaluate end-user interactions with lighting control interfaces, the antecedent factors that help form it, and its applications. The concept of tangible interaction is employed to distinguish between notions of usability and end-user experience; we argue that both have an impact on the overall effectiveness of lighting control interfaces. Usability is concerned with easier understanding of control functions. Enduser experience is concerned with explicating the quality of end-users’ experience such as fun and pleasure of use. Survey research and experimental mock-ups were used to design experiments that enabled endusers to evaluate their own interactions with conventional lighting control interfaces. End-user responses obtained from these experiments challenge manufacturers’ claims about the effectiveness of conventional lighting control interfaces, and reveal a different way of thinking about future interface designs. Such a change in thinking could lead to lighting control interfaces that are easier to understand and more pleasurable to use. A set of measures for future empirical testing is provided that is general enough to allow researchers to create measures for other aspects related to end-user interactions beyond those targeted in this paper.

VISUAL SALIENCY OF URBAN OBJECTS AT NIGHT: IMPACT OF THE DENSITY OF BACKGROUND LIGHT PATTERNS

NAVAZ DAVOUDIAN

As with other types of visual design, lighting design considers the relationship between objects and their context. With outdoor lighting design it is relevant to consider how background lighting might influence the perception of urban objects, and thus influence lighting design decisions. Previous studies have shown that salience is strongly influenced by visual context: the same target may or may not be salient, depending on how it is embedded in a scene. Experimental work was carried out to determine the impact of background density of lighting patterns on the visual saliency of the target and also interaction between the density of light patterns and luminance contrast in object saliency. The result shows that the visual saliency of illuminated urban objects is significantly reduced by increasing the density of background light pattern.

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