ASTM E1455-17(2022)
(Practice)Standard Practice for Obtaining Colorimetric Data from a Visual Display Unit Using Tristimulus Colorimeters
Standard Practice for Obtaining Colorimetric Data from a Visual Display Unit Using Tristimulus Colorimeters
SIGNIFICANCE AND USE
5.1 This practice may be applied when tristimulus colorimeters are used to measure the colors produced on self-luminous video display devices such as CRTs and flat-panel displays, including electroluminescent (EL) panels, light emitting diodes (LEDs) field emission displays (FEDs), and back-lit liquid crystal displays (LCDs). This practice is not meant to be a complete description of a procedure to measure the color coordinates of a display. Rather, it provides a method for obtaining more accurate results when certain conditions are met. It may be used by any person engaged in the measurement of color on display devices who has access to the requisite equipment.
5.2 This practice defines a class of tristimulus colorimeters that may be said to be compatible with this practice.
SCOPE
1.1 This practice is intended as an aid for improving the accuracy of colorimetric measurements made with tristimulus colorimeters on visual display units, such as cathode ray tubes (CRTs) and self-luminous flat-panel displays. It explains a useful step in the analysis of colorimetric data that takes advantage of the fact that light from such displays consists of an additive mixture of three primary colored lights. However, it is not a complete specification of how such measurements should be made.
1.2 This practice is limited to display devices and colorimetric instruments that meet linearity criteria as defined in the practice. It is not concerned with effects that might cause measurement bias such as temporal or geometric differences between the instrument being optimized and the instrument used for reference.
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E1455 − 17 (Reapproved 2022)
Standard Practice for
Obtaining Colorimetric Data from a Visual Display Unit
Using Tristimulus Colorimeters
This standard is issued under the fixed designation E1455; 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
This practice provides directions for correcting the results obtained with tristimulus colorimeters
when measuring the tristimulus values or chromaticity coordinates of colored displays. Tristimulus
colorimeters approximate the CIE color matching functions x¯(λ), y¯(λ), z¯(λ) to make these measure-
ments. The errors generated in measuring colors on a display may be minimized using this practice.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 This practice is intended as an aid for improving the
E284 Terminology of Appearance
accuracy of colorimetric measurements made with tristimulus
E1336 Test Method for Obtaining Colorimetric Data From a
colorimeters on visual display units, such as cathode ray tubes
Visual Display Unit by Spectroradiometry
(CRTs) and self-luminous flat-panel displays. It explains a
E1341 Practice for Obtaining Spectroradiometric Data from
useful step in the analysis of colorimetric data that takes
Radiant Sources for Colorimetry
advantage of the fact that light from such displays consists of
2.2 ISO/CIE Standard:
an additive mixture of three primary colored lights. However,
ISO 11664–1:2007(E)/CIE S 014–1/E:2006 Joint Standard
it is not a complete specification of how such measurements
ISO/CIE Standard: Colorimetry Part 1 – CIE Standard
should be made.
Colorimetric Observers
1.2 This practice is limited to display devices and colori-
3. Terminology
metric instruments that meet linearity criteria as defined in the
practice. It is not concerned with effects that might cause
3.1 Definitions—Unless otherwise stated, definitions of ap-
measurement bias such as temporal or geometric differences
pearance terms in Terminology E284 are applicable to this
between the instrument being optimized and the instrument
practice.
used for reference.
3.2 Definitions of Terms Specific to This Standard:
1.3 This standard does not purport to address all of the 3.2.1 calibration, n—in reference to a tristimulus
safety concerns, if any, associated with its use. It is the
colorimeter, the process performed outside of this practice to
responsibility of the user of this standard to establish appro- adjust the tristimulus colorimeter to provide the best possible
priate safety, health, and environmental practices and deter-
results for average or predefined conditions.
mine the applicability of regulatory limitations prior to use.
3.2.2 compatible, adj—in reference to a tristimulus
1.4 This international standard was developed in accor-
colorimeter, one so designed as to automate the procedure
dance with internationally recognized principles on standard-
described in this practice.
ization established in the Decision on Principles for the
3.2.3 optimization, n—in reference to a tristimulus
Development of International Standards, Guides and Recom-
colorimeter, the process performed pursuant to this practice to
mendations issued by the World Trade Organization Technical
adjust the tristimulus colorimeter or to interpret its readings to
Barriers to Trade (TBT) Committee.
provide better results when applied to a particular display
device.
1 2
This practice is under the jurisdiction of ASTM Committee E12 on Color and For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Appearance and is the direct responsibility of Subcommittee E12.06 on Display, contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Imaging and Imaging Colorimetry. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved June 1, 2022. Published June 2022. Originally the ASTM website.
approved in 1992. Last previous edition approved in 2017 as E1455 – 17. DOI: Currently available from CIE (Commission International on Illumination),
10.1520/E1455-17R22. http://www.techstreet.com.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1455 − 17 (2022)
4. Summary of Practice 6.1.2 No matter how many filters are used, or in what
manner, the goal of the measurement process is to determine
4.1 Tristimulus colorimeters comprised of three or four
tristimulus values X, Y, Z. For light with a color stimulus
detector channels are, in general, not amenable to accurate
function Φ(λ),
calibration that holds for all manner of usage with different
830 nm
illuminated devices and objects. This is because the spectral
X 5 k Φ λ x¯ λ dλ (1)
* ~ ! ~ !
responsivities of their detector channels do not exactly match
360 nm
the defined Commission Internationale de L’Éclairage (CIE)
830 nm
x¯(λ), y¯(λ), z¯(λ) functions. Factory or subsequent calibration
Y 5 k Φ λ y¯ λ dλ
* ~ ! ~ !
reflects judgments and compromises that may not be readily
360 nm
apparent. Nevertheless, this practice provides guidance on how
830 nm
such a tristimulus colorimeter may be optimized for use with a
Z 5 k * Φ~λ!z¯~λ!dλ
particular video display device, providing better accuracy with
360 nm
that device than its more general calibration provides. An
where:
optimization matrix transforms the instrumental (measured)
k is 683 lm/W for emissive devices, such as displays, and x¯ λ ,
~ !
CIE X, Y, Z values into adjusted X, Y, Z values that are closer
y¯~λ!, z¯~λ! are color-matching functions. While the standard
to the ideal. This matrix is determined by reference to a
definition of X, Y, Z requires the use of the CIE 1931 2°
colorimeter with higher intrinsic accuracy. The method derives
color-matching functions, the mathematics described in this
from the fact that the color stimulus functions from display
practice would also be applicable to any other set of color-
devices are linear combinations of three primary functions and
matching functions, such as the CIE 1964 10° functions.
are not entirely arbitrary.
These equations (Eq 1) are defined by ISO in its Standard
5. Significance and Use
ISO 11664–1:2007(E)/CIE S 014–1E:2006 and the CIE in its
publication Publ. 015(1).
5.1 This practice may be applied when tristimulus colorim-
6.1.3 In practice, color measurement instruments compute
eters are used to measure the colors produced on self-luminous
X, Y, Z by the summation of the signals as measured through
video display devices such as CRTs and flat-panel displays,
the various filters, each signal being multiplied by an appro-
includingelectroluminescent(EL)panels,lightemittingdiodes
priate calibration factor. In matrix notation:
(LEDs) field emission displays (FEDs), and back-lit liquid
X C C C . C F
m X1 X2 X3 Xf 1
crystal displays (LCDs). This practice is not meant to be a
Y C C C . C F
5 (2)
complete description of a procedure to measure the color m Y1 Y2 Y3 Yf 2
F G F G
Z C C C . C F
coordinates of a display. Rather, it provides a method for m Z1 Z2 Z3 Zf 3
¡
obtaining more accurate results when certain conditions are
3 4
F
met.Itmaybeusedbyanypersonengagedinthemeasurement
f
of color on display devices who has access to the requisite
where:
equipment.
F , F , F , through F are the electrical signals from the f
1 2 3 f
filtered detectors and the C are calibration coefficients. X ,
5.2 This practice defines a class of tristimulus colorimeters
ij m
Y , Z have subscripts to indicate that they are measured
that may be said to be compatible with this practice.
m m
values rather than ideal ones.
6.1.4 In this practice, we presume that the color measuring
6. Background of Practice
instrument is linear: that each signal F is strictly proportional
a
6.1 Colorimetry:
to the received optical power, that any zero-offset (background
6.1.1 Color measurement instruments consist, in general, of
in darkness) is removed, that the proportionality for signal F
a
means to measure radiometric power as transmitted through a
is not affected by the value of signal F , and in the case of
b
number of bandpass filters. Most commonly, electrical devices
closely packed detectors (such as charge-coupled device
are used to measure the filtered light. They may be used with
(CCD) detector elements) no signal F spills over and affects
a
different filters in succession, or multiple devices may be used
signal F as it approaches saturation. These presumptions are
b
concurrently. In instruments called spectroradiometers, the
amenable to experimental verification using methods beyond
radiometric power is measured through a large number (typi-
the scope of this practice (2).
cally 30 to 500) of narrowband filters. (Practice E1341 de-
6.1.5 The values of the matrix elements C may be deter-
ij
scribeshowamonochromatororpolychromator(spectrograph)
mined using criteria that depends on the design and intended
may be employed to filter and measure light in separate bands
application of the instrument. The full extent of this subject is
on the order of 1-nm wide.) In instruments called tristimulus beyond the scope of this practice. However, in general, for
colorimeters, the radiometric power is measured through three spectroradiometers (f ≈ 30 to 500), C reflects the tabulated
Xj
or four wideband filters. These filters may be constructed from value of (λ) near the center wavelength of Filter j as well as the
dispersive elements (prisms and gratings) or from materials
with selective spectral transmission or reflection. The latter
may be either uniform or comprised of different patches, in a 4
The boldface numbers in parentheses refer to the list of references at the end of
mosaic pattern, that provide the desired overall effect. this standard.
E1455 − 17 (2022)
spectral responsivity of the corresponding detector channel. 6.2.2 Thedisplayelectronicsvary a, b, coverthefaceofthe
(Likewise, C and C vary with (λ).) For tristimulus display in order to generate a colored image. For this practice,
Yj Zj
colorimeters, the choice of C is discussed further, below.As a we presume that the display electronics may be set to make a,
ij
general matter, the instrument designer should choose pass- b, c uniform (perhaps after averaging nonobvious fine-
bands and matrix elements that balance accuracy, sensitivity, structure) over a sufficient area of the display to permit
and other design requirements. measurements to be made on that area.
6.2.3 It is a requirement for the applicability of this practice
6.1.6 Tristimulus colorimeters are generally designed with
that the display device behaves as stated in Eq 6. This practice
filters that are intended to match the spectral responsivities of
does not represent that any particular display device will act as
their detector channels to the CIE color matching functions.
predicted by Eq 6, though those within the mentioned classes
For such an instrument,
of devices might do so. The procedure for experimental
X C 00 F
m X1 1
verification of this property for a specific display device is
Y 0 C 0 F
5 (3)
m Y2 2
F G F GF G
beyond the scope of this practice (3).
Z 00 C F
m Z3 3
6.3 Colorimetric Measurement of Displays:
where:
6.3.1 Each of the primary color stimulus functions Φ (λ),
r
the non-zero C matrix elements represent adjustable gains of
ij
Φ (λ), Φ (λ)stimulatesresponsesinthe fdetectorchannelsthat
g b
the detector channels. However, the x¯(λ) function has two
may be represented by a vectorF (that is,F ,F ,F ). Given
r g b
distinctlobes.Thismaybedealtwithbysplittingthelobesinto
their construction, these vectors are linearly independent.
two functions, x¯ (λ) and x¯ (λ), each with a separate filter
short long (None of the three can be expressed as a linear combination of
(F and F , respectively). For such an instrument,
1 2
the other two.) While F is an element of an f-dimensional
vector space, it is clear that only a three-dimensional subspace
X C C 00 F
m X1 X2 1
is spanned by the F’s of all possible color stimulus functions
Y 00 C 0 F
5 (4)
m Y3 2
F G F G
following Eq 6. Further, the mapping of F into (X , Y , Z )
Z 000 C F m m m
m Z4 3
3 4
space by Eq 2 remains three dimensional. In other words, there
F
is a one-to-one mapping of the vector (a, b, c) onto (X, Y, Z)by
Alternatively, the z¯(λ) function properly scaled may serve as
application of Eq 1; and, for a particular instrument with a
the x¯ (λ), since they have a similar shape,
short fixed calibration matrixC, there is also a one-to-one mapping
of the vector (a, b, c) onto (X , Y , Z ). From this we deduce
X C 0 C F
m m m
m X1 X3 1
that a matrixR exists that can be used to translate (X , Y , Z )
Y 0 C 0 F m m m
5 (5)
m Y2 2
F G F GF G
values into actual (X, Y, Z) values.
Z 00 C F
m Z3 3
6.3.2 A colorimeter that takes advantage of this fact must
In all of these cases, it is difficult to realize an exact match
provide means for implementing the matrix R. That is, all f
between the CIE color-matching functions and the actual
filtered detector signals should contribute linearly toward the
spectral responsivities of the corresponding detector channels.
computation of each output, X , Y , Z , instead of using
m m m
This means that no choice of C will provide perfect calibra-
ij different detectors for each output. This idea was reported as
tion for all applications of the instrument. The criteria for
long ago as 1973 by Wagner (4), and it has been expanded
setting the C might not be well documented for a particular
ij upon and rediscovered by others since then (5-10).
instrument.
6.3.3 On the basis of this property, a tristimulus colorimeter
6.1.7 It is generally believed that spectroradiometers, with
can be optimized for use on a self-luminous display by the
their many detector channels, may be calibrated to yield proper derivation of a matrixR for that display.We proceed on
superior measurements of X, Y, Z for diverse applications.
theassumptionsthatthecomponentsaresufficientlystable,and
Nevertheless, the relative simplicity of tristimulus colorimeters that similarly built displays have similar enough spectral
and their commensurately lower cost have made them popular
primaries to make a derivation of R worthwhile. However,
where the highest accuracy is not required. these assumptions should be quantified before accuracy claims
are made in any specific situation.
6.2 Self-Luminous Displays:
6.3.4 On t
...
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