In this paper, a replication of the color-constancy study of Arend and Reeves (1986) is reported. and an alternative method is presented that can be used for the study of higher order aspects of color constancy, such as memory, familiarity, and perceptual organization. Besides a simultaneous presentation of standard and test illuminants, we also carried out an experiment in which the illuminants were presented successively. The results were similar to Arend and Reeves's; however, in the object-matching condition of the successive experiment, we found an overestimation, instead of an underestimation, of the illuminant component. Because the results of matching experiments are difficult to interpret, mainly due to their sensitivity to instruction effects, we introduced another type of color-constancy task. In this task, subjects simply named the color of a simulated patch. It was found that, by applying such a task, a reliable measure of the degree of identification of object color can be obtained.Color constancy is the phenomenon that the color appearance of objects is invariant, notwithstanding variations in illumination. In real-life situations, variations in illumination occur very often. For example, the spectral composition of daylight changes with the weather, the season, and the time of the day. The artificial lights in our environment have many different spectral characteristics as well. In all these cases, the visual system tends to perceive objects with constant colors.Color constancy poses a problem, because the object component and the illuminant component of the light that reaches the eye are not separately available to the observer. In recent attempts to model color constancy (e.g.,
The aim of this article is to improve our understanding of user-centered design (UCD) adoption and provide accordingly useful advice to the UCD community. UCD adoption was investigated through a Web survey. The results show that the early involvement of UCD practitioners in the product life cycle is more frequent compared to 10 years ago. It is also true that the methods and the techniques employed have shifted their focus from summative evaluation to rapid development cycles and from quantitative to qualitative evaluation methods. Based on the survey, there are several organizational factors UCD practitioners and their management should consider. UCD should be part of the business strategy and supported by higher management. Usability goals must be set through competitive analysis and practitioners should be rewarded if goals are reached or exceeded. For bespoke systems, usability goals should be explicitly discussed with the customer. Special attention should be paid to communication inside and outside the company so as to clarify the outcomes and benefits of the UCD approach.
The primary contribution of this paper is investigating how the User Centered Design approach is integrated into the industry. Employing a structured web-survey, targeted to the usability practitioners, we find out that UCD is particularly employed in big companies, but with a relatively low ratio: practitioners represent less than one percent of the company employees. User interviews and both low and high fidelity prototyping are the most frequently used techniques. We eventually validate our hypothesis that UCD integration is facilitated by factors related to management support, infrastructure and communication; companies interested in producing better usable and fit-for-use products should take all of these issues into serious consideration.
Dannemiller's (1989) computational approach to color constancy is discussed in relation to human color constancy. A reflectance channel that requires a priori information is shown to be less plausible for the human visual system than Dannemiller argued. The resemblance of Dannemiller's hypothetical visual system to the human visual system is misleading because it implies that surface reflectance is the illuminant-invariant object color descriptor that the human visual system uses to achieve color constancy. However, an alternative type of descriptor is available that is not used to recover reflectance spectra. It has the advantage of allowing an interpretation that is preferable from a human perceptual point of view.
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