SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTS
➤ Gửi thông báo lỗi ⚠️ Báo cáo tài liệu vi phạmNội dung chi tiết: SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTS
SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTS
Surface Color Perception andEnvironmental ConstraintsLaurence T. MaloneyDepartment of Psychology Center for Neural Science New York University New Yor SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTSrk. NY 10003ltm@cns.nyu.eduDraft: May 22, 2000In Colour Vision: Front Light to Object. Mausfeld, R. & Heyer, D. [Eds.] Oxford: Oxford University Press, in press.Surface Color Perception in Constrained Environments... / shall now remind you, that I did not deny, but that colour might in some sense be SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTS considered a quality residing in the body that is said to be coloured.— Robert Boyle (1663)If you and I were to disagree concerning the lengths of twSURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTS
o rods, we might send out for a measuring tape or arrange to put the two rods next to each other so that they could be directly compared. In contrast,Surface Color Perception andEnvironmental ConstraintsLaurence T. MaloneyDepartment of Psychology Center for Neural Science New York University New Yor SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTSd in for consultation, could readily provide a summary of how a small, designated patch of a surface interacts with light, its bidirectional reflectance density' function, s Á;v, I I. This bi-directional reflectance density function (BRDF) is, roughly speaking, the probability1 that a photon of wave SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTSlength Ả , arriving at the surface from direction / . will be re-emitted in the direction of the viewer V (See Fig. 1). It is plausible to assume thatSURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTS
, if there is an objective correlate of the perceived color of a surface, the intrinsic color of the surface (Shepard. 1992). then some computation apSurface Color Perception andEnvironmental ConstraintsLaurence T. MaloneyDepartment of Psychology Center for Neural Science New York University New Yor SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTSility densities, not probabilities. It is the probability that photons arriving along a narrow cone centered on the vector / will be re-emitted along a narrow cone centered on the vector V . See Cohen & Wallace (1993).Surface Color Perception in Constrained Environments3In the quotation that heads t SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTShis chapter, the celebrated chemist Robert Boyle allows for the possibility that colors correspond to objective properties of surfaces, but is evidentSURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTS
ly uncertain as to how that could be. Indeed, the argument to the contrary has considerable force. There is considerable psychophysical evidence indicSurface Color Perception andEnvironmental ConstraintsLaurence T. MaloneyDepartment of Psychology Center for Neural Science New York University New Yor SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTS scene (Kelson and Judd. 1936). atmospheric haze (Brown & MacLeod, 1997). and the presence or absence of other surfaces not directly involved in the judgment, among other factors. These effects arc not small: ‘If changes in illumination arc sufficiently great, surface colors may become radically alt SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTSered ... [W]cakly or moderately selective illuminants with respect to wavelength leave surface colors relatively unchanged ... but a highly selectiveSURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTS
ilhiminant may make two surfaces which appear different in daylight indistinguishable, and surfaces of the same daylight color widely different' (KelsSurface Color Perception andEnvironmental ConstraintsLaurence T. MaloneyDepartment of Psychology Center for Neural Science New York University New Yor SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTSts that the relation between the BRDF of a surface patch and its perceived color is slight: there are no intrinsic colors.Evans (1948. Color plate 13) illustrates how saturated, bright objects can change color dramatically with a change in illuminant: yellow becomes red. green becomes neutral. Nassa SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTSu (1983. Color plate) includes a color photograph of the gemstone alexandrite which can appear emerald green under daylight and ruby red under ordinarSURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTS
y, indoor, incandescent illumination.Yet we need not visit a laboratory to observe large failures of color and lightness' constancy. When you attend aSurface Color Perception andEnvironmental ConstraintsLaurence T. MaloneyDepartment of Psychology Center for Neural Science New York University New Yor SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTS the surfaces in: Lightness, roughly speaking, refers to the light-dark dimension of surface color perception (Gilchrist, 1994). Throughout this chapter I will use rhe term "surface color" to refer to hlack, white, and grey stimuli as well as surfaces tliat are colored in the everyday use of the ter SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTSm.Surface Color Perception in Constrained Environments4front of you likely corresponds to the filmmaker's conception of the film. You see people, carsSURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTS
.explosions, and so on. just as the script of the film predicted. None of these objects or their surfaces are present, and yet you ’see' them, occasioSurface Color Perception andEnvironmental ConstraintsLaurence T. MaloneyDepartment of Psychology Center for Neural Science New York University New Yor SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTSpear to be any and all colors in rapid succession. The failure of constancy in your perception of surface color could not be larger.Mathematical analyses (Ives. 1912; Sãllstrõm. 1973; Maloney, 1984) confinn this conclusion: it is simply not possible to go from the kind of information available to bi SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTSological visual systems to estimates of properties of the BRDFs of surfaces without some restriction on possible illuminants and possible surfaces inSURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTS
scenes. There cannot be objective correlates of perceived surface color (intrinsic surface colors) that a biological visual system can estimate under Surface Color Perception andEnvironmental ConstraintsLaurence T. MaloneyDepartment of Psychology Center for Neural Science New York University New Yor SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTSates that, under certain circumstances, human observers do seem to estimate intrinsic surface colors accurately (Brainard. Brunt & Speigle. 1997; Brainard. 1998). Other species are known to exhibit some degree of color constancy (Neumeyer. 1981; Werner. 1990).We can reconcile the apparent impossibil SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTSity of surface color perception in ’arbitrary' environments with the evident competence exhibited by human observers and other animals in psychophysicSURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTS
al experiments and much of everyday life by recognizing that we do not live in ’arbitrary environments'. It is specific constraints present in our immSurface Color Perception andEnvironmental ConstraintsLaurence T. MaloneyDepartment of Psychology Center for Neural Science New York University New Yor SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTS concerning a visual scene. If all of the assertions on the list are true of theSurface Color Perception in Constrained Environments5scene, then human color vision will assign colors to surfaces in that scene that are the same as those it assigns to these surfaces in another scene that also satisfie SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTSs these assertions. Judd (1940). for example, notes that with “moderate departures from daylight in the spectral distribution of energy in the ilhiminSURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTS
ant. external objects are seen ... nearly in their natural, daylight colors." In making this statement. Judd dichotomizes scenes into those satisfyingSurface Color Perception andEnvironmental ConstraintsLaurence T. MaloneyDepartment of Psychology Center for Neural Science New York University New Yor SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTSearly the same color to any surface patch as in any other. Judd’s specification is not correct (the spectral distribution of the light used in projecting a movie is not from daylight) but it seems plausible that it can be extended to a description of the scenes where our color visual system assigns SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTSintrinsic colors to surfaces. If we succeed, then we have established an operating range for the human color visual system, which I will refer to as iSURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTS
ts environment, over which it is capable of assigning stable colors to surfaces.With no further specification of what that environment might be. this Surface Color Perception andEnvironmental ConstraintsLaurence T. MaloneyDepartment of Psychology Center for Neural Science New York University New Yor SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTSry experiment. We explain observed failures of color constancy by asserting that the ‘environment was bad’, and we explain success by asserting that the ‘environment was good.’The environmental hypothesis has scientific content only to the extent that we can precisely state, in advance, what it is a SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTSbout an environment that permits or precludes accurate surface color perception. For human vision, this environment does not include movie theaters orSURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTS
the conditions of many psychophysical experiments. It does include the conditions of much of our everyday color experience, but, as we shall see, notSurface Color Perception andEnvironmental ConstraintsLaurence T. MaloneyDepartment of Psychology Center for Neural Science New York University New Yor SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTSnmental constraints, the mathematical possibility of accurate surface color perception, and human performance in color tasks in real and simulated environments. Four new areas of research have emerged. The first comprises development of algorithms that make use of explicit constraints in estimating SURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTSproperties of the BRDF (See Hurlbert. 1998; Maloney. 1999 for reviews). If the constraints corresponding to an algorithm are satisfied, then the algorSURFACE COLOR PERCEPTION AND ENVIRONMENTAL CONSTRAINTS
ithm can estimate intrinsic colors of surfaces. Once beyond its operating range, an algorithm will typically fail; the link between its color estimateGọi ngay
Chat zalo
Facebook