ASTM E1499-97(2009)
(Guide)Standard Guide for Selection, Evaluation, and Training of Observers
Standard Guide for Selection, Evaluation, and Training of Observers
SIGNIFICANCE AND USE
The term appearance (see 3.2.1) implies the essential presence of human visual observations. The results of visual observation involve not only the step of observing, accomplished by the eye, but also the inseparable step of interpretation in the brain. Instrumental test methods currently cannot duplicate this second step, and therefore can now only approximate, but not fully measure, appearance. Such instrumental measures of appearance properties are useful only to the extent that they can be correlated to the results of visual observations by observers of the appearance phenomena being evaluated.
Almost invariably, too little attention has been paid to ensuring that the essential visual observations have been properly obtained to provide the basis for correlating visual and instrumental test results. (The only recent book devoted to visual measurements (1) has no index entry for observer.)
This guide provides the means for assessing observers, by outlining the requirements and tests for their selection, evaluation, and training. This guide should be useful to all experimenters designing or using visual test methods to provide either direct results in terms of the observation of appearance properties, or the experiments correlating such results with instrumental measures approximating the same appearance properties.
SCOPE
1.1 This guide describes criteria and tests for selecting, evaluating, and training human visual-sensory observers for tasks involving the perception and scaling of properties and phenomena relating to appearance.
1.2 Examples of tests requiring the use of trained observers include but are not limited to those described in the following ASTM standards: on color, Practice D1535 and Practice E1360; on color difference, Practice D1729 and Test Method D2616; on gloss, Test Method D4449; on metamerism, Practice D4086; and on setting tolerances, Practice D3134.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: E1499 − 97 (Reapproved2009)
Standard Guide for
Selection, Evaluation, and Training of Observers
This standard is issued under the fixed designation E1499; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
3.1 Definitions—Definitions of appearance terms in Termi-
1.1 This guide describes criteria and tests for selecting,
nology E284 are applicable to this guide.
evaluating, and training human visual-sensory observers for
tasks involving the perception and scaling of properties and
3.2 Definitions of Terms Specific to This Standard:
phenomena relating to appearance.
3.2.1 appearance, n—in psychophysical studies, perception
inwhichthespectralandgeometricaspectsofavisualstimulus
1.2 Examples of tests requiring the use of trained observers
are integrated with its illuminating and viewing environment.
include but are not limited to those described in the following
3.2.2 observer, n—one who judges visually, qualitatively or
ASTM standards: on color, Practice D1535 and Practice
quantitatively, the content of one or more appearance attributes
E1360; on color difference, Practice D1729 and Test Method
in each member of a set of objects or stimuli.
D2616; on gloss, Test Method D4449; on metamerism, Prac-
tice D4086; and on setting tolerances, Practice D3134.
3.2.3 scale, v—to assess the content of one or more appear-
ance attributes in the members of a set of stimuli.
1.3 This standard does not purport to address all of the
3.2.3.1 Discussion—Alternatively, scales may be deter-
safety concerns, if any, associated with its use. It is the
mined by assessing the difference in content of an attribute
responsibility of the user of this standard to establish appro-
with respect to the differences in that attribute among the
priate safety and health practices and determine the applica-
members of the set.
bility of regulatory limitations prior to use.
4. Summary of Guide
2. Referenced Documents
4.1 This guide provides descriptions of techniques and tests
2.1 ASTM Standards:
for the selection of candidates for observers for use in visual
D1535 Practice for Specifying Color by the Munsell System
testing, for the evaluation of their capabilities in this field, and
D1729 Practice for Visual Appraisal of Colors and Color
for their training to enhance these capabilities.
Differences of Diffusely-Illuminated Opaque Materials
4.2 Discussion is provided of precautions required for the
D2616 Test Method for Evaluation of Visual Color Differ-
efficientuseofobserversinvisualtests,includingavoidanceof
ence With a Gray Scale
overtaxing the observers and the control of test variables.
D3134 Practice for Establishing Color and Gloss Tolerances
D4086 Practice for Visual Evaluation of Metamerism
4.3 Other considerations of test design, including the num-
D4449 Test Method for Visual Evaluation of Gloss Differ-
bers of observers and observations required and the precision
ences Between Surfaces of Similar Appearance
of the visual results, are to be covered elsewhere.
E284 Terminology of Appearance
E1360 Practice for Specifying Color by Using the Optical 5. Significance and Use
Society of America Uniform Color Scales System
5.1 The term appearance (see 3.2.1) implies the essential
presence of human visual observations. The results of visual
observation involve not only the step of observing, accom-
This guide is under the jurisdiction of ASTM Committee E12 on Color and
plished by the eye, but also the inseparable step of interpreta-
Appearance and is the direct responsibility of Subcommittee E12.11 on Visual
tion in the brain. Instrumental test methods currently cannot
Methods.
duplicate this second step, and therefore can now only
Current edition approved Dec. 1, 2009. Published December 2009. Originally
approximate, but not fully measure, appearance. Such instru-
approved in 1992. Last previous edition approved in 2003 as E1499 – 97 (2003).
DOI: 10.1520/E1499-97R09.
mentalmeasuresofappearancepropertiesareusefulonlytothe
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
extent that they can be correlated to the results of visual
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
observations by observers of the appearance phenomena being
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. evaluated.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1499 − 97 (2009)
NOTE 1—An abnormal match point may be considered one that fails to
5.2 Almost invariably, too little attention has been paid to
fall within the main groupings of observer match points for the light
ensuring that the essential visual observations have been
source used on either Fig. 3 of Ref (5) or the figure of Ref (6). Note,
properlyobtainedtoprovidethebasisforcorrelatingvisualand
however, that this criterion is specific to the originalD&H Color Rule
instrumental test results. (The only recent book devoted to
and does not apply to the currently available MatchPoint Rule.
visual measurements (1) has no index entry for observer.)
6.2.3 Farnsworth-Munsell 100 Hue Test—The Farnsworth-
5,8
5.3 This guide provides the means for assessing observers,
Munsell 100 HueTest (7) should next be administered to the
by outlining the requirements and tests for their selection,
candidate. While the pseudoisochromatic-plate tests isolate
evaluation, and training. This guide should be useful to all
certainfactorsofcolordeficiency,theFarnsworth-Munsell100
experimenters designing or using visual test methods to pro-
Hue Test measures color discrimination directly and in detail.
vide either direct results in terms of the observation of
This test was not designed strictly for pass-fail categorization
appearance properties, or the experiments correlating such
of observers but is recommended as an adjunct test for the
results with instrumental measures approximating the same
analysis of color defectives. (It is also useful as an observer
appearance properties.
evaluation test; see 6.3.1.) In the Farnsworth-Munsell 100 Hue
Test, abnormal color vision is indicated by the observer’s
6. Selection and Evaluation of Observers
failure to place the test chips in correct order.The chips consist
6.1 Theprocessusedforselectingobserversdependsagreat of 85 colored papers varying in hue at approximately constant
deal upon the type of experiment being carried out, but should valueandchroma,andtheobserver’sfailureisusuallybywide
essentially evaluate the potential capability of the observer to margins in one or more limited regions of the hue circle. The
execute a series of visual evaluation tasks (2, 3). When these presenceofsuchabnormalresultsofthetestshouldbegrounds
tasks involve appearance attributes, color or related spectral for dismissing the candidate observer.
phenomena are often among the task subjects, and if instead
6.3 Visual Acuity and Discrimination Tests—Having deter-
geometric phenomena such as gloss are involved, many of the
mined that the candidate observers have normal color vision, it
same considerations apply. Accordingly, the emphasis in this
is next necessary to test their level of discrimination of small
guide is upon selecting observers for color-related measure-
differences in color or another appearance attribute of interest.
ments. Thus, observers must be screened to rule out those with
6.3.1 Farnsworth-Munsell 100 Hue Test—Use of the
any color- or task-oriented deficiencies.
Farnsworth-Munsell 100 Hue Test as a color-discrimination
6.2 Color Vision Tests (4):
test does not require readministration of the test, but merely
6.2.1 Pseudoisochromatic Plates—As a preliminary color
reexamination of the test results. For the purposes of assessing
4,5,6
vision test, a pseudoisochromatic-plate test should be
color (more precisely, hue) discrimination, the test results are
administered to the candidate observers. The instructions and
examined for the presence of an approximately constant but
scoring techniques supplied by the manufacturer should be
significant error level in the arrangement of the test chips
followed. In particular, the illumination level should be kept
throughout the hue circle. This may be interpreted as an
well within the photopic range (1000 1x is recommended as a
inability to discriminate the small color differences between
minimum value) and the spectral quality of the illuminating
neighboring chips. While a weakness of this type might, for
source should be near that of north-sky daylight. Failure to
example, interfere with an observer’s ability to participate in
identify correctly the required number of the plates in the test
threshold scaling experiments, the observer might still be
used should be considered grounds for dismissing the candi-
competent to perform magnitude scaling of larger differences
date observer.
among specimens.
6.2.2 Color Rule Test—When the anticipated experiment
6.3.2 Triangle Test—This test is part of a series known as
involves observing in the object mode, the candidate observer
5,9
the Japanese Color Aptitude Test. The candidate observers
should be asked to find a (metameric) match on a Color Rule.
are shown, one at a time, a series of 20 sets of three colored
Astandardlightsourceshouldbeused,similartothatspecified
chips each. In each set, two of the chips are identical and the
in the majority of tests for which the observer is being trained.
third is slightly different in color. The observer is asked to
It should be remembered that normal trichromats will report
identify which one is different, the differences being so small
match points that are dependent on age (5), but any abnormal
that there is considerable uncertainty in the judgment.Alower
match point should be considered grounds for dismissing the
than average score in this test indicates that the observer does
candidate observer.
not differentiate small differences well.
The boldface numbers in parentheses refer to the list of references at the end of
this standard. D & H Color Rule (no longer available); MatchPoint Rule (available 1990 but
The sole source of supply of the Dvorine Pseudo-Isochromatic Plates, known not equivalent to the D& H Rule), available from Munsell Laboratory, Macbeth
to the committee at this time is The Psychological Corp., Harcourt Brace Division, Kollmorgen Instruments Corp., 405 Little Britain Road, New Windsor,
Jovanovich, 555 Academic Court, San Antonio, TX 78204. NY 12553-6148.
5 8
If you are aware of alternative suppliers, please provide this information to The sole source of supply of the Farnsworth-Munsell 100 Hue Test, known to
ASTM International Headquarters. Your comments will receive careful consider- the committee at this time is Munsell Laboratory, Macbeth Division, Kollmorgen
ation at a meeting of the responsible technical committee, which you may attend. Instruments Corp., 405 Little Britain Rd., New Windson, NY 12553-6148.
6 9
The sole source of supply of the H-R-R Pseudoisochromatic plates, Ishihara The sole source of supply of the Japanese Color Aptitude Test (1994 edition),
Color-Blindness Tests, known to the committee at this time is Richmond Products known to the committee at this time is Japan Color Research Institute, 3-1-19
Inc., 1021 S. Rogers Circle, Suite 6, Boco Raton, FL 33484. Nishiazabu, Minato-ku, Tokyo 106, Japan.
E1499 − 97 (2009)
6.3.3 HVC (Hue, Value, and Chroma) Color Vision Skill 7. Training of Observers
5,10
Test—The HVC Color Vision Skill Test is designed to
7.1 The importance of following the steps of selection and
assess the ability of the observer to discriminate between
evaluation of observers by training sessions using the exact
specimens having small color differences in hue, value, and
conditions of the scaling experiment in accordance with
chroma. The test is a general indicator of accuracy in making
Section 6 cannot be overemphasized. The details of these
color matches. It consists of a set of 36 loose specimens for
training sessions will depend on the experimental design being
one-at-a-time comparison with 36 mounted specimens in a
used and cannot be stated in general terms here. Examples are
prescribed sequence. The specimens are of one of four hues
found in Refs (2) and (3). Only by training the observer under
(blue, red, green, and yellow) with nine specimens each in
the actual experimental conditions to be used can that observer
subgroups that vary in hue, value, and chroma around a center
learn exactly what is expected in the task.
point. The color differences among the specimens correspond 7.1.1 It is recommended that each observer make a dummy
roughly to industrial color matching tolerances. set of observations before each observing session. This has
several advantages. The first few observations always exhibit
6.4 Magnitude Scaling Tests:
more “noise,” as the observer refamiliarizes himself with the
6.4.1 Length Estimation—A simple magnitude-scaling test
task. Use of the same sample set for each of these preliminary
may be devised to familiarize the observer with scaling
observation sets allows consistency to be tested and puts the
procedures and the experimental task of matching a given
observer at ease. At least one such set of observations should
anchor scale with a perceived difference in stimuli. In an
be one from which the results are discarded. The experimenter
example (2), the observer was asked to judge the apparent
should watch the observer during the first session to be sure
length of a line in comparison to the length of a standard line. that the instructions for the experiment are understood.
The lines were drawn with a heavy black marker on 100 by 7.1.2 There appears to be virtually no information reported
in Refs (1-3), (9-12) about several important aspects of
150-mmindexcards,onelinetoeachof21cards.Thestandard
observer training, such as how long the training sessions need
or anchor line, 125 mm long, was assigned a value of 10 units
tobe,whentheyshouldoccur,whethertheyshouldberepeated
of length. The other 20 cards had lines of various lengths, both
and at what intervals, and how the experimenter knows when
longerandshorterthantheanchorline.Theanchorandonetest
the observer is adequately trained. A few comments on the
card were displayed side by side at a distance of 0.6 m. Of
number of observers required in a typical case are given in Ref
course, no rulers or other aids were allo
...
This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:E1499–97(Reapproved2003) Designation: E1499 – 97 (Reapproved 2009)
Standard Guide for
Selection, Evaluation, and Training of Observers
This standard is issued under the fixed designation E1499; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This guide describes criteria and tests for selecting, evaluating, and training human visual-sensory observers for tasks
involving the perception and scaling of properties and phenomena relating to appearance.
1.2 ExamplesoftestsrequiringtheuseoftrainedobserversincludebutarenotlimitedtothosedescribedinthefollowingASTM
standards: on color, Practice D1535 and Practice E1360; on color difference, Practice D1729 and Test Method D2616; on gloss,
Test Method D4449; on metamerism, Practice D4086; and on setting tolerances, Practice D3134.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D1535 Practice for Specifying Color by the Munsell System
D1729 Practice for Visual Appraisal of Colors and Color Differences of Diffusely-Illuminated Opaque Materials
D2616 Test Method for Evaluation of Visual Color Difference With a Gray Scale
D3134 Practice for Establishing Color and Gloss Tolerances
D4086 Practice for Visual Evaluation of Metamerism
D4449 Test Method for Visual Evaluation of Gloss Differences Between Surfaces of Similar Appearance
E284 Terminology of Appearance
E1360 Practice for Specifying Color by Using the Optical Society of America Uniform Color Scales System
3. Terminology
3.1 Definitions—Definitions of appearance terms in Terminology E284 are applicable to this guide.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 appearance, n—in psychophysical studies, perception in which the spectral and geometric aspects of a visual stimulus are
integrated with its illuminating and viewing environment.
3.2.2 observer, n—one who judges visually, qualitatively or quantitatively, the content of one or more appearance attributes in
each member of a set of objects or stimuli.
3.2.3 scale, v—to assess the content of one or more appearance attributes in the members of a set of stimuli.
3.2.3.1 Discussion—Alternatively, scales may be determined by assessing the difference in content of an attribute with respect
to the differences in that attribute among the members of the set.
4. Summary of Guide
4.1 Thisguideprovidesdescriptionsoftechniquesandtestsfortheselectionofcandidatesforobserversforuseinvisualtesting,
for the evaluation of their capabilities in this field, and for their training to enhance these capabilities.
4.2 Discussion is provided of precautions required for the efficient use of observers in visual tests, including avoidance of
overtaxing the observers and the control of test variables.
4.3 Other considerations of test design, including the numbers of observers and observations required and the precision of the
visual results, are to be covered elsewhere.
This guide is under the jurisdiction of ASTM Committee E12 on Color and Appearance and is the direct responsibility of Subcommittee E12.11 on Visual Methods.
Current edition approved Dec. 1, 2003.2009. Published December 2003.2009. Originally approved in 1992. Last previous edition approved in 19972003 as
E1499 – 97 (2003). DOI: 10.1520/E1499-97R039.
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E1499 – 97 (2009)
5. Significance and Use
5.1 The term appearance (see 3.2.1) implies the essential presence of human visual observations. The results of visual
observation involve not only the step of observing, accomplished by the eye, but also the inseparable step of interpretation in the
brain. Instrumental test methods currently cannot duplicate this second step, and therefore can now only approximate, but not fully
measure, appearance. Such instrumental measures of appearance properties are useful only to the extent that they can be correlated
to the results of visual observations by observers of the appearance phenomena being evaluated.
5.2 Almost invariably, too little attention has been paid to ensuring that the essential visual observations have been properly
obtained to provide the basis for correlating visual and instrumental test results. (The only recent book devoted to visual
measurements (1) has no index entry for observer.)
5.3 Thisguideprovidesthemeansforassessingobservers,byoutliningtherequirementsandtestsfortheirselection,evaluation,
and training.This guide should be useful to all experimenters designing or using visual test methods to provide either direct results
in terms of the observation of appearance properties, or the experiments correlating such results with instrumental measures
approximating the same appearance properties.
6. Selection and Evaluation of Observers
6.1 The process used for selecting observers depends a great deal upon the type of experiment being carried out, but should
essentially evaluate the potential capability of the observer to execute a series of visual evaluation tasks (2, 3). When these tasks
involve appearance attributes, color or related spectral phenomena are often among the task subjects, and if instead geometric
phenomena such as gloss are involved, many of the same considerations apply. Accordingly, the emphasis in this guide is upon
selecting observers for color-related measurements. Thus, observers must be screened to rule out those with any color- or
task-oriented deficiencies.
6.2 Color Vision Tests (4):
4,5,6
6.2.1 Pseudoisochromatic Plates—As a preliminary color vision test, a pseudoisochromatic-plate test should be adminis-
tered to the candidate observers. The instructions and scoring techniques supplied by the manufacturer should be followed. In
particular, the illumination level should be kept well within the photopic range (1000 1x is recommended as a minimum value)
and the spectral quality of the illuminating source should be near that of north-sky daylight. Failure to identify correctly the
required number of the plates in the test used should be considered grounds for dismissing the candidate observer.
6.2.2 Color Rule Test—When the anticipated experiment involves observing in the object mode, the candidate observer should
be asked to find a (metameric) match on a Color Rule. A standard light source should be used, similar to that specified in the
majority of tests for which the observer is being trained. It should be remembered that normal trichromats will report match points
that are dependent on age (5), but any abnormal match point should be considered grounds for dismissing the candidate observer.
NOTE 1—An abnormal match point may be considered one that fails to fall within the main groupings of observer match points for the light source
used on either Fig. 3 of Ref (5) or the figure of Ref (6). Note, however, that this criterion is specific to the original D & H Color Rule and does not apply
to the currently available MatchPoint Rule.
,
5 8
6.2.3 Farnsworth-Munsell 100 Hue Test—The Farnsworth-Munsell 100 Hue Test (7) should next be administered to the
candidate. While the pseudoisochromatic-plate tests isolate certain factors of color deficiency, the Farnsworth-Munsell 100 Hue
Testmeasurescolordiscriminationdirectlyandindetail.Thistestwasnotdesignedstrictlyforpass-failcategorizationofobservers
butisrecommendedasanadjuncttestfortheanalysisofcolordefectives.(Itisalsousefulasanobserverevaluationtest;see6.3.1.)
In the Farnsworth-Munsell 100 Hue Test, abnormal color vision is indicated by the observer’s failure to place the test chips in
correctorder.Thechipsconsistof85coloredpapersvaryinginhueatapproximatelyconstantvalueandchroma,andtheobserver’s
failure is usually by wide margins in one or more limited regions of the hue circle. The presence of such abnormal results of the
test should be grounds for dismissing the candidate observer.
6.3 VisualAcuity and Discrimination Tests—Havingdeterminedthatthecandidateobservershavenormalcolorvision,itisnext
necessary to test their level of discrimination of small differences in color or another appearance attribute of interest.
6.3.1 Farnsworth-Munsell 100 Hue Test—Use of the Farnsworth-Munsell 100 Hue Test as a color-discrimination test does not
require readministration of the test, but merely reexamination of the test results. For the purposes of assessing color (more
precisely,hue)discrimination,thetestresultsareexaminedforthepresenceofanapproximatelyconstantbutsignificanterrorlevel
The boldface numbers in parentheses refer to the list of references at the end of this standard.
The sole source of supply of the Dvorine Pseudo-Isochromatic Plates, known to the committee at this time is The Psychological Corp., Harcourt Brace Jovanovich, 555
Academic Court, San Antonio, TX 78204.
If you are aware of alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration at a
meeting of the responsible technical committee,1 which you may attend.
The sole source of supply of the H-R-R Pseudoisochromatic plates, Ishihara Color-BlindnessTests, known to the committee at this time is Richmond Products Inc., 1021
S. Rogers Circle, Suite 6, Boco Raton, FL 33484.
D & H Color Rule (no longer available); MatchPoint Rule (available 1990 but not equivalent to the D& H Rule), available from Munsell Laboratory, Macbeth Division,
Kollmorgen Instruments Corp., 405 Little Britain Road, New Windsor, NY 12553-6148.
The sole source of supply of the Farnsworth-Munsell 100 Hue Test, known to the committee at this time is Munsell Laboratory, Macbeth Division, Kollmorgen
Instruments Corp., 405 Little Britain Rd., New Windson, NY 12553-6148.
E1499 – 97 (2009)
inthearrangementofthetestchipsthroughoutthehuecircle.Thismaybeinterpretedasaninabilitytodiscriminatethesmallcolor
differences between neighboring chips. While a weakness of this type might, for example, interfere with an observer’s ability to
participate in threshold scaling experiments, the observer might still be competent to perform magnitude scaling of larger
differences among specimens.
,
5 9
6.3.2 Triangle Test—This test is part of a series known as the Japanese Color Aptitude Test. The candidate observers are
shown, one at a time, a series of 20 sets of three colored chips each. In each set, two of the chips are identical and the third is
slightly different in color. The observer is asked to identify which one is different, the differences being so small that there is
considerable uncertainty in the judgment.Alower than average score in this test indicates that the observer does not differentiate
small differences well.
,
5 10
6.3.3 HVC (Hue, Value, and Chroma) Color Vision Skill Test—The HVC Color Vision Skill Test is designed to assess the
ability of the observer to discriminate between specimens having small color differences in hue, value, and chroma. The test is a
generalindicatorofaccuracyinmakingcolormatches.Itconsistsofasetof36loosespecimensforone-at-a-timecomparisonwith
36 mounted specimens in a prescribed sequence. The specimens are of one of four hues (blue, red, green, and yellow) with nine
specimenseachinsubgroupsthatvaryinhue,value,andchromaaroundacenterpoint.Thecolordifferencesamongthespecimens
correspond roughly to industrial color matching tolerances.
6.4 Magnitude Scaling Tests:
6.4.1 Length Estimation—Asimple magnitude-scaling test may be devised to familiarize the observer with scaling procedures
and the experimental task of matching a given anchor scale with a perceived difference in stimuli. In an example (2), the observer
was asked to judge the apparent length of a line in comparison to the length of a standard line. The lines were drawn with a heavy
blackmarkeron100by150-mmindexcards,onelinetoeachof21cards.Thestandardoranchorline,125mmlong,wasassigned
a value of 10 units of length. The other 20 cards had lines of various lengths, both longer and shorter than the anchor line. The
anchor and one test card were displayed side by side at a distance of 0.6 m. Of course, no rulers or other aids were allowed. The
observer’staskwastoassignavaluetothelengthofeachlinerelativetothatof10unitsassignedtotheanchor.Meansofassessing
the data obtained from a test such as this are discussed by Lodge (8).
6.4.2 Color Estimation—Another set of 20 cards from the Japanese Color Aptitude Test may be used to assess the candidate
observer’s “feel” for the type of judgment required in magnitude scaling of an appearance attribute.These cards each contain three
color chips in a horizontal row. The left-hand chip is identified with the value 1, and the right-hand chip with the value 10. The
chip in the middle lies between these two ends on some color-attribute scale. The task is to assign a scale value between 1 and
10 to the center chip. The color-attribute scales of hue, value, and chroma are used randomly in the set.
6.5 The results of the above magnitude-scaling tests should be compared to the observer’s performance on the color-
discrimination tests, particularly the Farnsworth-Munsell 100 Hue Test, to determine how observers with superior to normal color
vision perform. Any significant disparities should be examined to see if they resulted from poor directions or improper viewing
conditions. If this was not the case, the observer should be asked to repeat the judgments at another time. If the results are poor
a second time, the conclusion may be drawn that the candidate does not have a substantial skill for this type of judgment, and this
observer should be dismissed.
7. Training of Observers
7.1 The importance of following the steps of selection and evaluation of observers by training sessions
...
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