ASTM E2175-01(2008)
(Practice)Standard Practice for Specifying the Geometry of Multiangle Spectrophotometers
Standard Practice for Specifying the Geometry of Multiangle Spectrophotometers
SIGNIFICANCE AND USE
This practice is for the use of manufacturers and users of instruments to measure the appearance of gonioapparent materials, those writing standard specifications for such instruments, and others who wish to specify precisely the geometric conditions of multiangle spectrophotometry. A prominent example of industrial usage is the routine application of such measurements by material suppliers and automobile manufacturers to measure the colors of metallic paints and plastics.
SCOPE
1.1 This practice provides a way of specifying the angular and spatial conditions of measurement and angular selectivity of a method of measuring the spectral reflectance factors of opaque gonioapparent materials, for a small number of sets of geometric conditions.
1.2 Measurements to characterize the appearance of retroreflective materials are of such a special nature that they are treated in other ASTM documents and are not included in the scope of this standard.
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:E2175 −01(Reapproved2008)
Standard Practice for
Specifying the Geometry of Multiangle Spectrophotometers
This standard is issued under the fixed designation E2175; 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.
INTRODUCTION
The appearance of metallic coatings and plastics usually depends on the directions of illumination
and viewing, a phenomenon called “gonioappearance.” This phenomenon is also observed with other
materials, such as lustrous textiles and materials containing pearlescent or interference pigments. The
characteristic appearance of most such materials is accentuated by directional illumination, such as
that provided by the sun on a clear day or a small lamp at night. The variation in color, as a function
of geometry, is usually measured by spectrophotometry with several specified sets of geometric
conditions. Measurement of this kind, at a few selected angles, is called “multiangle
spectrophotometry,”asdistinguishedfrommeasurementoverabroadrangeofangles,whichiscalled“
goniospectrophotometry.” Spectrophotometric aspects of these measurements, including spectral
resolution and linearity of photometric scales, are treated in other standards, including Practice E308
and Practice E1164. Practice E1767 provides practice for specifying the geometry of measurements.
Retroreflectors exhibit a special kind of gonioappearance, which is treated in otherASTM documents.
The present document provides standard practice for specifying influx and efflux angles, angular
selectivity, spatial distributions of illuminators and receivers, and angular aspects of standardizing the
photometric scale, that are peculiar to multiangle spectrophotometry. Directional illumination
emphasizes the gonioappearance of most materials, but when interference pigments are used, such as
those used in ink to mark paper currency, the effect is observed with diffuse illumination and varying
angles of viewing, so these materials are also measured with diffuse illumination.
1. Scope responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
1.1 This practice provides a way of specifying the angular
bility of regulatory limitations prior to use.
and spatial conditions of measurement and angular selectivity
of a method of measuring the spectral reflectance factors of
2. Referenced Documents
opaque gonioapparent materials, for a small number of sets of
2.1 ASTM Standards:
geometric conditions.
E284 Terminology of Appearance
1.2 Measurements to characterize the appearance of retrore-
E308 PracticeforComputingtheColorsofObjectsbyUsing
flective materials are of such a special nature that they are
the CIE System
treated in other ASTM documents and are not included in the
E1164 PracticeforObtainingSpectrometricDataforObject-
scope of this standard.
Color Evaluation
E1767 Practice for Specifying the Geometries of Observa-
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the tion and Measurement to Characterize the Appearance of
Materials
This practice is under the jurisdiction of ASTM Committee E12 on Color and
Appearance and is the direct responsibility of Subcommittee E12.03 on Geometry. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Jan. 1, 2008. Published January 2008. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2001. Last previous edition approved in 2001 as E2175 - 01. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/E2175-01R08. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2175−01(2008)
3. Terminology ture” and the center of that area is designated the origin, o, of
the geometric space used to specify the configuration. The
3.1 Fordefinitionsofappearancetermsusedinthispractice,
normal to the sampling aperture, at the origin, is the -z-axis.
refer to Terminology E284.
Angles subtended at the origin and measured from that normal
are called “anormal angles.” The specular direction is the
4. Significance and Use
direction of the beam from a directional illuminator after
4.1 Thispracticeisfortheuseofmanufacturersandusersof
specular reflection by an ideal plane mirror at the sampling
instruments to measure the appearance of gonioapparent ma-
aperture.Anglessubtendedattheoriginandmeasuredfromthe
terials, those writing standard specifications for such instru-
specular direction are called“ aspecular angles” and are posi-
ments, and others who wish to specify precisely the geometric
tive in sign when measured in the direction toward the normal.
conditions of multiangle spectrophotometry. A prominent ex-
The normal and the axis of a directional illuminator define a
ample of industrial usage is the routine application of such
plane, known as the “plane of incidence.” The specular
measurements by material suppliers and automobile manufac-
direction necessarily lies in that plane.
turers to measure the colors of metallic paints and plastics.
6.1.1 To facilitate simple and precise geometric specifica-
tion of the sampling aperture, it shall be either circular or
5. Components of Apparatus
rectangular.
5.1 The apparatus shall consist of one or more illuminators
6.1.2 To facilitate simple and precise geometric specifica-
and one or more spectrometric receivers at fixed or adjustable
tion of directional influx or efflux distributions, they shall be
angleswithrespecttoareferenceplane,ameansofpositioning
either conical or pyramidal. For purposes of describing geom-
specimens in a reference plane, a means of indicating the area
etry by functional notation, a diffuse distribution may be
on the specimen to be measured, shielding to avoid stray light,
considered a conical distribution centered on the normal and
and a means of displaying spectral or colorimetric data and/or
having a half angle of 90 degrees.
communicating such data to a data-recorder or computer. (The
6.1.3 In a uniplanar configuration, a directional illuminator
terms“ light,” “illuminator,” “illumination,” and “illuminance”
is used, the axes of the receivers lie in the plane of incidence,
are used here for simplicity, though the corresponding terms
and their positions are specified by aspecular angles. A
“radiant power,” “irradiator,” “irradiation,” and “irradiance”
uniplanar configuration is illustrated in Fig. 1. To simplify the
would be more accurate when the incident flux includes
figure, only one receiver is shown.
ultraviolet flux, as is necessary if the appearance of a fluores-
cent material is measured.) 6.1.3.1 For a conical influx distribution, the flux incident on
the origin comes from an area of a directional illuminator
6. Geometric Types of Apparatus
uniformly filling a circle on a plane normal to the beam. For a
conical efflux distribution, flux from the origin is uniformly
6.1 The geometric configuration of the instrument may be
collected and evaluated over an area of the receiver that is a
uniplanar, annular, circumferential, or diffuse. In all cases, the
circle on a plane normal to the beam.Auniplanar configuration
specimen is taken to be a flat surface lying in a plane called the
with conical influx and efflux distributions is illustrated in Fig.
“reference plane,” which is designated the x, y plane. When
2. To simplify the figure, only one receiver is shown.
there is a single directional illuminator, the x direction is the
direction of the projection of the axis of the incident beam on 6.1.3.2 For a pyramidal influx distribution, flux incident on
the reference plane. If there are several directional illuminators the origin comes from an area of a directional illuminator
or a single diffuse illuminator, the direction of the x-axis must uniformlyfillingarectangleonaplanenormaltothebeam.For
be selected and specified. The area of the reference plane on a pyramidal efflux distribution, flux from the origin is uni-
which measurements are made is called the “sampling aper- formly collected and evaluated over an area of the receiver that
FIG. 1Uniplanar Configuration
E2175−01(2008)
FIG. 2Uniplanar Configuration with Conical Influx and Efflux Distributions
is a rectangle on a plane normal to the beam. A pyramidal having their axes at the same anormal angle, but arrayed at
configuration can be used to subtend a small angle in the plane various azimuthal angles. The nominal angle of incidence is
of incidence, to enhance angular selectivity, but have a large
measured from the normal to the axes of the illuminators. For
enough solid angle to provide adequate flux for reliable
multiangle spectrophotometry, provision must be made for
measurements.Auniplanarconfigurationwithpyramidalinflux
illuminators at several different nominal angles. A circumfer-
and efflux distributions is illustrated in Fig. 3. To simplify the
ential configuration with three illuminators is illustrated in Fig.
figure, only one receiver is shown and the angles δ and ϵ are
4.To simplify the figure, the anglesκ,θ, andη are shown for
i i i
shown for the receiver, but not for the illuminator.
the first illuminator only.
6.1.4 In an annular configuration, the incident beam uni-
6.1.5.1 The discrete illuminators shall all have the same
formly fills the space between two right-circular cones, with
nominal angle of incidence, for a given measurement.
their axes on the normal and apices at the origin. An annular
6.1.6 In a diffuse configuration, the incident flux is diffuse.
configuration can be used to provide a flux distribution with a
Ideally, the illuminator illuminates the sampling aperture at all
small range of anormal angles, to enhance anormal angular
angles within the hemisphere on the -z side of the reference
selectivity, but of larg
...
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:E2175–01 Designation: E 2175 – 01 (Reapproved 2008)
Standard Practice for
Specifying the Geometry of Multiangle Spectrophotometers
This standard is issued under the fixed designation E 2175; 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 (e) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
The appearance of metallic coatings and plastics usually depends on the directions of illumination
and viewing, a phenomenon called “gonioappearance.” This phenomenon is also observed with other
materials, such as lustrous textiles and materials containing pearlescent or interference pigments. The
characteristic appearance of most such materials is accentuated by directional illumination, such as
that provided by the sun on a clear day or a small lamp at night. The variation in color, as a function
of geometry, is usually measured by spectrophotometry with several specified sets of geometric
conditions. Measurement of this kind, at a few selected angles, is called “multiangle spectrophotom-
etry,” as distinguished from measurement over a broad range of angles, which is called“ goniospec-
trophotometry.” Spectrophotometric aspects of these measurements, including spectral resolution and
linearity of photometric scales, are treated in other standards, including Practice E 308 and Practice
E 1164. Practice E 1767 provides practice for specifying the geometry of measurements. Retroreflec-
tors exhibit a special kind of gonioappearance, which is treated in other ASTM documents. The
present document provides standard practice for specifying influx and efflux angles, angular
selectivity, spatial distributions of illuminators and receivers, and angular aspects of standardizing the
photometric scale, that are peculiar to multiangle spectrophotometry. Directional illumination
emphasizes the gonioappearance of most materials, but when interference pigments are used, such as
those used in ink to mark paper currency, the effect is observed with diffuse illumination and varying
angles of viewing, so these materials are also measured with diffuse illumination.
1. Scope
1.1 This practice provides a way of specifying the angular and spatial conditions of measurement and angular selectivity of a
method of measuring the spectral reflectance factors of opaque gonioapparent materials, for a small number of sets of geometric
conditions.
1.2 Measurements to characterize the appearance of retroreflective materials are of such a special nature that they are treated
in other ASTM documents and are not included in the scope of this standard.
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:
E 284 Terminology of Appearance
E 308 Practice for Computing the Colors of Objects by Using the CIE System
E 1164 Practice for Obtaining SpectrophotometricSpectrometric Data for Object-Color Evaluation
E 1767 Practice for Specifying the GeometryGeometries of Observations and Measurements to Characterize theAppearance of
Materials
3. Terminology
3.1 For definitions of appearance terms used in this practice, refer to Terminology E 284.
This practice is under the jurisdiction of ASTM Committee E12 on Color and Appearance and is the direct responsibility of Subcommittee E12.03 on Geometry.
Current edition approved Dec. 10, 2001. Published February 2002.
Current edition approved Jan. 1, 2008. Published January 2008. Originally approved in 2001. Last previous edition approved in 2001 as E 2175 - 01.
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at service@astm.org. For Annual Book ofASTM Standards
, Vol 06.01.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.
E 2175 – 01 (2008)
4. Significance and Use
4.1 This practice is for the use of manufacturers and users of instruments to measure the appearance of gonioapparent materials,
those writing standard specifications for such instruments, and others who wish to specify precisely the geometric conditions of
multiangle spectrophotometry. A prominent example of industrial usage is the routine application of such measurements by
material suppliers and automobile manufacturers to measure the colors of metallic paints and plastics.
5. Components of Apparatus
5.1 Theapparatusshallconsistofoneormoreilluminatorsandoneormorespectrometricreceiversatfixedoradjustableangles
with respect to a reference plane, a means of positioning specimens in a reference plane, a means of indicating the area on the
specimen to be measured, shielding to avoid stray light, and a means of displaying spectral or colorimetric data and/or
communicating such data to a data-recorder or computer. (The terms“ light,” “illuminator,” “illumination,” and “illuminance” are
used here for simplicity, though the corresponding terms “radiant power,” “irradiator,” “irradiation,” and “irradiance” would be
more accurate when the incident flux includes ultraviolet flux, as is necessary if the appearance of a fluorescent material is
measured.)
6. Geometric Types of Apparatus
6.1 The geometric configuration of the instrument may be uniplanar, annular, circumferential, or diffuse. In all cases, the
specimen is taken to be a flat surface lying in a plane called the “reference plane,” which is designated the x, y plane. When there
is a single directional illuminator, the x direction is the direction of the projection of the axis of the incident beam on the reference
plane. If there are several directional illuminators or a single diffuse illuminator, the direction of the x-axis must be selected and
specified. The area of the reference plane on which measurements are made is called the “sampling aperture” and the center of
that area is designated the origin, o, of the geometric space used to specify the configuration.The normal to the sampling aperture,
at the origin, is the -z-axis. Angles subtended at the origin and measured from that normal are called “anormal angles.” The
specular direction is the direction of the beam from a directional illuminator after specular reflection by an ideal plane mirror at
the sampling aperture.Angles subtended at the origin and measured from the specular direction are called“ aspecular angles” and
are positive in sign when measured in the direction toward the normal. The normal and the axis of a directional illuminator define
a plane, known as the “plane of incidence.” The specular direction necessarily lies in that plane.
6.1.1 To facilitate simple and precise geometric specification of the sampling aperture, it shall be either circular or rectangular.
6.1.2 To facilitate simple and precise geometric specification of directional influx or efflux distributions, they shall be either
conical or pyramidal. For purposes of describing geometry by functional notation, a diffuse distribution may be considered a
conical distribution centered on the normal and having a half angle of 90 degrees.
6.1.3 In a uniplanar configuration, a directional illuminator is used, the axes of the receivers lie in the plane of incidence, and
their positions are specified by aspecular angles.Auniplanar configuration is illustrated in Fig. 1. To simplify the figure, only one
receiver is shown.
6.1.3.1 Foraconicalinfluxdistribution,thefluxincidentontheorigincomesfromanareaofadirectionalilluminatoruniformly
filling a circle on a plane normal to the beam. For a conical efflux distribution, flux from the origin is uniformly collected and
evaluated over an area of the receiver that is a circle on a plane normal to the beam.Auniplanar configuration with conical influx
and efflux distributions is illustrated in Fig. 2. To simplify the figure, only one receiver is shown.
6.1.3.2 For a pyramidal influx distribution, flux incident on the origin comes from an area of a directional illuminator uniformly
filling a rectangle on a plane normal to the beam. For a pyramidal efflux distribution, flux from the origin is uniformly collected
and evaluated over an area of the receiver that is a rectangle on a plane normal to the beam.Apyramidal configuration can be used
FIG. 1 Uniplanar Configuration
E 2175 – 01 (2008)
FIG. 2 Uniplanar Configuration with Conical Influx and Efflux Distributions
to subtend a small angle in the plane of incidence, to enhance angular selectivity, but have a large enough solid angle to provide
adequate flux for reliable measurements. A uniplanar configuration with pyramidal influx and efflux distributions is illustrated in
Fig. 3. To simplify the figure, only one receiver is shown and the angles d and e are shown for the receiver, but not for the
illuminator.
6.1.4 In an annular configuration, the incident beam uniformly fills the space between two right-circular cones, with their axes
on the normal and apices at the origin. An annular configuration can be used to provide a flux distribution with a small range of
anormal angles, to enhance anormal angular selectivity, but of large enough solid angle to provide adequate flux for reliable
measurements. The nominal angle of an annular distribution is the average of the half-angles of the two defining cones. For
multiangle spectrophotometry, provision must be made for several annular distributions with different nominal angles. The efflux
distribution is a conical distribution with its axis on the normal and its apex at the origin.
6.1.5 Acircumferential configuration approximates a
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