1、Designation: E1808 96 (Reapproved 2015)Standard Guide forDesigning and Conducting Visual Experiments1This standard is issued under the fixed designation E1808; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisi
2、on. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide is intended to help the user decide on the typeof viewing conditions, visual scaling methods, and analysisthat should
3、be used to obtain reliable visual data.1.2 This guide is intended to illustrate the techniques thatlead to visual observations that can be correlated with objectiveinstrumental measurements of appearance attributes of objects.The establishment of both parts of such correlations is anobjective of Com
4、mittee E12.1.3 Among ASTM standards making use of visual observa-tions are Practices D1535, D1729, D3134, D4086, and E1478;Test Methods D2616, D3928, and D4449; and Guide E1499.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsi
5、bility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1535 Practice for Specifying Color by the Munsell SystemD1729 Practice for Visual Appraisal of
6、 Colors and ColorDifferences of Diffusely-Illuminated Opaque MaterialsD2616 Test Method for Evaluation of Visual Color Differ-ence With a Gray ScaleD3134 Practice for Establishing Color and Gloss TolerancesD3928 Test Method for Evaluation of Gloss or SheenUniformityD4086 Practice for Visual Evaluati
7、on of MetamerismD4449 Test Method for Visual Evaluation of Gloss Differ-ences Between Surfaces of Similar AppearanceE284 Terminology of AppearanceE1478 Practice for Visual Color Evaluation of TransparentSheet MaterialsE1499 Guide for Selection, Evaluation, and Training ofObservers3. Terminology3.1 T
8、he terms and definitions in Terminology E284 areapplicable to this guide.3.2 Definitions:3.2.1 appearance, nin psychophysical studies, perceptionin which the spectral and geometric aspects of a visual stimulusare integrated with its illuminating and viewing environment.3.2.2 observer, none who judge
9、s visually, qualitatively orquantitatively, the content of one or more appearance attributesin each member of a set of stimuli.3.2.3 sample, na small part or portion of a material orproduct intended to be representative of the whole.3.2.4 scale, vto assess the content of one or more appear-ance attr
10、ibutes in the members of a set of stimuli.3.2.4.1 DiscussionAlternatively, scales may be deter-mined by assessing the difference in content of an attributewith respect to the differences in that attribute among themembers of the set.3.2.5 specimen, na piece or portion of a sample used tomake a test.
11、3.2.6 stimulus, nany action or condition that has thepotential for evoking a response.3.3 Definitions of Terms Specific to This Standard:3.3.1 anchor, nthe stimulus from which a just-perceptibledifference is measured.3.3.2 anchor pair, na pair of stimuli differing by a definedamount, to which the di
12、fference between two test stimuli iscompared.3.3.3 interval scale, na scale having equal intervals be-tween elements.3.3.3.1 DiscussionLogical operations such as greater-than, less-than, equal-to, and addition and subtraction can beperformed with interval-scale data.3.3.4 law of comparative judgment
13、san equation relatingthe proportion of times any stimulus is judged greater, accord-ing to some attribute, than any other stimulus in terms ofjust-perceptible differences.1This guide is under the jurisdiction of ASTM Committee E12 on Color andAppearance and is the direct responsibility of Subcommitt
14、ee E12.11 on VisualMethods.Current edition approved Nov. 1, 2015. Published November 2015. Originallyapproved in 1996. Last previous edition approved in 2009 as E1808 96 (2009).DOI: 10.1520/E1808-96R15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Serv
15、ice at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.3.5 nominal scale, nscale in which items ar
16、e scaledsimply by name.3.3.5.1 DiscussionOnly naming can be performed withnominal-scale data.3.3.6 ordinal scale, na scale in which elements are sortedin order based on more or less of a particular attribute.3.3.6.1 DiscussionLogical operations such as greater-than, less-than, or equal-to can be per
17、formed with ordinal-scaledata.3.3.7 psychometric function, nthe function, typicallysigmoidal, relating the probability of detecting a stimulus to thestimulus intensity.3.3.8 psychophysics, nthe study of the functions relatingthe physical measurements of stimuli and the sensations andperceptions the
18、stimuli evoke.3.3.9 ratio scale, na scale which, in addition to theproperties of other scales, has a meaningfully defined zeropoint.3.3.9.1 DiscussionIn addition to the logical operationsperformable with other types of data, multiplication anddivision can be performed with ratio-scale data.3.3.10 sc
19、ale, na defined arrangement of the elements of aset of stimuli or responses.4. Summary of Guide4.1 This guide provides an overview of experimental designand data analysis techniques for visual experiments. Carefullyconducted visual experiments allow accurate quantitativeevaluation of perceptual phen
20、omena that are often thought ofas being completely subjective. Such results can be of immensevalue in a wide variety of fields, including the formulation ofcolored materials and the evaluation of the perceived quality ofproducts.4.2 This guide includes a review of issues regarding thechoice and desi
21、gn of viewing environments, an overview ofvarious classes of visual experiments, and a review of experi-mental techniques for threshold, matching, and scaling experi-ments. It also reviews data reduction and analysis procedures.Three different threshold and matching techniques areexplained, the meth
22、ods of adjustment, limits, and constantstimuli. Perceptual scaling techniques reviewed includeranking, graphical rating, category scaling, pairedcomparisons, triadic combinations, partitioning, and magnitudeestimation or production. Brief descriptions and examples,along with references to more detai
23、led literature, are given onthe appropriate types of data analysis for each experimentaltechnique.4.3 For reviews of topics in other than visual sensory testingwithin ASTM, see Refs (1, 2).35. Viewing Conditions5.1 Light SourceThe illumination of the specimens inscaling experiments must be reproduci
24、ble over the course ofthe experiments. To achieve this, it is essential to control boththe spectral character and the amount of illumination closely inboth space and time. Failure to accomplish this can seriouslyundermine the integrity of the experiments. The spectral powerdistribution of the illumi
25、nation should be known or, if this isnot possible, the light source should be identified as to type andmanufacturer. Information such as daylight-corrected fluores-cent light, warm-white fluorescent light, daylight-filtered in-candescent light, incandescent light, etc., together with param-eters suc
26、h as correlated color temperature and color renderingindex, if available, should be noted in the report of theexperiment.5.2 Viewing GeometryAlmost all specimens exhibit somedegree of gonioapparent or goniochromatic variation; thereforethe illuminating and viewing angles must be controlled andspecif
27、ied. This is particularly important in the study of speci-mens exhibiting gloss variations, textiles showingdirectionality, or gonioapparent (containing metallic or pearl-escent pigments) or retroreflective specimens, among others.This control and specification can range from correct position-ing of
28、 the source and observer and the elimination of anysecondary light sources visible in the specimens, for thejudgment of gloss specimens at and near the specular angle, tomore elaborate procedures specifying a range of angles andaperture angles of illumination and viewing for gonioapparentand retrore
29、flective specimens. When fluorescent specimens arestudied, the spectral power distribution of the source mustclosely match that of a designated standard source.5.3 Surround and Ambient FieldFor critical visual scalingwork, the surround, the portion of the visual field immediatelysurrounding the spec
30、imens, should have a color similar to thatof the specimens. The ambient field, the field of view when theobserver glances away from the specimens, should have aneutral color (Munsell Chroma less than 0.2) and a MunsellValue of N6 to N7 (luminous reflectance 29 to 42); see PracticeD1729).5.4 Observer
31、sGuide E1499 describes the selection,evaluation, and training of observers for visual scaling work.Of particular importance is the testing of the observers colorvision and their color discrimination for normality. Colorvision tests for this purpose are described in Guide E1499.6. Categories of Visua
32、l Experiments6.1 Visual experiments tend to fall into two broad classes:(1) threshold and matching experiments designed to measurevisual sensitivity to small changes in stimuli (or perceptualequality), and (2) scaling experiments intended to generate apsychophysical relationship between the perceptu
33、al and physi-cal magnitudes of a stimulus. It is critical to determine firstwhich class of experiment is appropriate for a given applica-tion.6.1.1 Threshold and Matching ExperimentsThreshold ex-periments are designed to determine the just-perceptible dif-ference in a stimulus, or JPD. Threshold tec
34、hniques are used tomeasure the observerssensitivity to a given stimulus.Absolutethresholds are defined as the JPD for a change from nostimulus, while difference thresholds represent the JPD from a3The boldface numbers in parentheses refer to a list of references at the end ofthis guide.E1808 96 (201
35、5)2particular stimulus level greater than zero. The stimulus fromwhich a difference threshold is measured is known as an anchorstimulus. Often, thresholds are measured with respect to thedifference between two stimuli. In such cases, the difference ofa pair of stimuli is compared to the difference i
36、n an anchor pair.Absolute thresholds are reported in terms of the physical unitsused to measure the stimulus, for example, a brightnessthreshold might be measured in luminance units of candelasper square metre. Sensitivity is measured as the inverse of thethreshold, since a low threshold implies hig
37、h sensitivity.Threshold techniques are useful for defining visual tolerances,such as color-difference tolerances. Matching techniques aresimilar, except that the goal is to determine when two stimuliare not perceptibly different. Measures of the variability inmatching can be used to estimate thresho
38、lds. Matching experi-ments provided the basis for CIE colorimetry through themetameric matches used to derive the color-matching functionsof the CIE standard observers.6.1.2 Scaling ExperimentsScaling experiments are in-tended to derive relationships between perceptual magnitudesand physical magnitu
39、des of stimuli. Several decisions must bemade, depending on the type and dimensionality of the scalerequired. It is important to identify the type of scale requiredand decide on the scaling method to be used before any scalingdata are collected. This seems to be an obvious point, but in therush to a
40、cquire data it is often overlooked, and later it may befound that the data obtained do not yield the answer required orcannot be used to perform desired mathematical operations.See Refs (3, 4) for further details. Scales are classified into thefollowing four classes:6.1.2.1 Nominal ScalesNominal sca
41、les are relativelytrivial in that they scale items simply by name. For color, anominal scale might consist of reds, yellows, greens, blues, andneutrals. Scaling in this case would simply require decidingwhich color belonged in which category. Only naming can beperformed with nominal data.6.1.2.2 Ord
42、inal ScalesOrdinal scales are scales in whichelements are sorted in ascending or descending order based onmore or less of a particular attribute. A box of multicoloredcrayons could be sorted by hue, and then in each hue family,say red, the crayons could be sorted from the lightest to thedarkest. In
43、a box of crayons the colors are not evenly spaced,so one might have, for example, three dark, one medium, andtwo light reds. If these colors were numbered from one to sixin increasing lightness, an ordinal scale would be created. Notethat there is no information on such a scale as to the magnitudeof
44、 difference from one of the reds to another, and it is clear thatthey are not evenly spaced. For an ordinal scale, it is sufficientthat the specimens be arranged in increasing or decreasingamounts of an attribute. The spacing between specimens can belarge or small and can change up and down the scal
45、e. Logicaloperations such as greater-than, less-than, or equal-to can beperformed with ordinal-scale data.6.1.2.3 Interval ScalesInterval scales have equal intervals.On an interval scale, if a pair of specimens were separated bytwo units, and a second pair at some other point on the scalewere also s
46、eparated by two units, the differences between thepair members would appear equal. However, there is nomeaningful zero point on an interval scale.Acommon exampleof an interval scale is the Celsius temperature scale. In additionto the mathematical operations listed for nominal and ordinalscales, addi
47、tion and subtraction can be performed withinterval-scale data.6.1.2.4 Ratio ScalesRatio scales have all the properties ofthe above scales plus a meaningfully defined zero point. Thusit is possible to equate ratios of numbers meaningfully with aratio scale. Ratio scales are often impossible to obtain
48、 in visualwork. An example of a ratio scale is the absolute, or Kelvin,temperature scale. All of the mathematical operations that canbe performed on interval-scale data can also be performed onratio-scale data, and in addition, multiplication and divisioncan be performed.7. Threshold and Matching Me
49、thods7.1 Several basic types of threshold experiments are pre-sented in this section in order of increasing complexity ofdesign and utility of the data generated. Many modifications ofthese techniques have been developed for specific applications.Experimenters should strive to design an experiment thatremoves as much control of the results from the observers aspossible, thus minimizing the influence of variable observerjudgment criteria. Generally, this comes at the cost of imple-menting a more complicated experimental procedure.7.1.1 Method of Adjus
