GB/T 39648-2020 PDF English
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GB/T 39648-2020: Textiles - Tests for colour fastness - Determination of colour fastness grades by digital imaging techniques
---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT39648-2020
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 59.080.01
CCS W 04
Textiles - Tests for colour fastness - Determination of colour
fastness grades by digital imaging techniques
(ISO 105-A11:2012, Textiles - Tests for colour fastness - Part A11:
Determination of colour fastness grades by digital imaging techniques, MOD)
ISSUED ON: DECEMBER 14, 2020
IMPLEMENTED ON: JULY 01, 2021
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration of the People's Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Terms and definitions... 5
4 Instruments and equipment ... 6
Annex A (normative) Grading of the degree of discoloration of the specimen ... 12
Annex B (normative) Evaluation of the degree of staining of the specimen ... 15
Annex C (normative) Verification chart ... 18
Annex D (informative) Summary of the international joint test report on the grading of
color fastness to digital imaging techniques ... 20
Bibliography... 22
Textiles - Tests for colour fastness - Determination of colour
fastness grades by digital imaging techniques
1 Scope
This Standard specifies the methods for evaluating the discoloration grade of the
specimen (according to Annex A) and the evaluation of the staining grade of the
standard backing fabric (according to Annex B) by digital imaging techniques in the
color fastness test. It also specifies the requirements of digital imaging system.
This Standard does not apply to the grading of light fastness tests of textiles.
NOTE: In the color fastness test of textiles described in the ISO 105B series of standards, the gray
sample card is not used for the discoloration assessment of the specimen.
This Standard describes the apparatus, equipment settings and calibration methods for
assessing discoloration and staining.
2 Normative references
The following referenced documents are indispensable for the application of this
document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
GB/T 6151, Textiles - Tests for colour fastness - General principles of testing (GB/T
6151-2016, ISO 105-A01:2010, MOD)
CIE S 012/E, Standard method of assessing the spectral quality of daylight
simulators for appraisal and measurement of colour
CIE 13.3,1995, Method of measuring and specifying the colour rendering properties
of light sources, 2nd edition
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 system grey
The color of the interior surface of the light source box and other instrument parts
visible in the captured image.
NOTE: This grey is roughly between N5 and N7 on the Monsey color chart. Under D65 light source
and CIE1964 standard chromaticity observation conditions, the CIELAB chromaticity value does
not exceed 2.5 in any hue direction; the CIELAB luminance value is within 50/70±2.
3.2 verification chart
A chart containing a series of patches of known chromaticity values.
3.3 system software
A software capable of controlling and operating a digital camera for inspection.
3.4 white tile
A plate that its color is certified and traceable to a national standard.
3.5 operator-selected area
During discoloration or staining gradings, the system software operator manually
selects the location and size of the test area in the reference and specimen.
3.6 automatic grading
The system software automatically grades the test area on the reference specimen and
test specimen during discoloration or staining grading.
4 Instruments and equipment
4.1 General
There is a calibrated digital camera in the test setup (4.2). It is installed in the
appropriate position of the light source box (4.3). The light source box provides a
controlled and continuous lighting environment. Specimens can be individually placed
in the light source box for grading. A group of specimens can also be graded
simultaneously by test type. The operator shall manually select the test area. An
example of the instrument structure diagram is shown in Figure 1.
If it is consistent with the operator's manual selection of the test area (3.5), the automatic
grading (3.6) method can be used.
The test instrument shall be maintained and calibrated in accordance with the
manufacturer's instructions and actual conditions.
operations. It shall have a storage function. Also, it can set the operating conditions of
different grading requirements.
4.2.2 Camera installation
The camera shall be installed on the top of the light source box (4.3), directly above the
specimen. The camera installation shall be capable of adjusting the position of the
camera lens so that the specimen grading area is parallel to the lens.
The installation height of the camera shall be such that an image of the entire grading
area can be obtained by properly adjusting the focal length of the camera.
4.2.3 Camera verification
4.2.3.1 General
The verification of the camera is to determine the accuracy of the CIEXYZ value of
each pixel in the output image of the camera. The verification result will be stored in
the system software. Images acquired during testing are graded accordingly. The
verification of the camera is based on the verification chart specified in Annex C.
4.2.3.2 Verification interval
The following shall be verified:
- After the digital imaging system is activated;
- After the camera's settings are changed;
- After the manufacturer's recommended calibration interval has been reached.
4.2.3.3 Verification time
The system software shall record the time and date of the current camera calibration
and make it available for review. When the verification time expires, the system
software shall automatically remind the user to perform the calibration.
4.2.3.4 Verification performance
Verification performance is expressed in terms of repeatability and accuracy of image
data. The verification result is expressed as the median and maximum value of
CIEDE2000 color difference. CIEDE2000 color difference is the difference between
the known value and the measured value of the digital verification chart. The system
software guides these verification tests.
The system software shall be able to store the current verification performance
parameters of the camera, so that the user can restore the current settings of the camera.
4.2.3.5 Accuracy test
The digital camera (4.2) shall be verified within the time period specified by the
manufacturer or within 8h intervals, whichever is the shorter time interval between the
two.
For each color block in the calibration color card, the CIEDE2000 color difference
value is tested by digital image method and spectrophotometric method, respectively.
The spectrophotometer shall be calibrated by means of the white tile (3.4). The
chromaticity value of this white tile (3.4) can be traced back to national standards.
The median and maximum values of CIEDE2000 chromatic aberration shall be
recorded for accuracy.
Accuracy shall meet the following requirements at the same time:
- The maximum value of CIEDE2000 is less than 5.0;
- The median value of CIEDE2000 is less than 1.0.
4.2.3.6 Repeatability test
The repeatability test shall be performed within the time period specified by the
manufacturer.
Make 10 consecutive measurements on the verification chart that meets the
requirements of Annex C. The digital imaging system shall measure and record all color
blocks used in the calibration.
Calculate the arithmetic mean of CIELABL*, a*, b*, c* and h for each color block.
Calculate the difference between the CIEDE2000 average and the individual
measurements for each block.
Calculate the median value of the CIEDE2000 color difference for each color block.
The median and maximum values of CIEDE2000 color difference shall be recorded to
indicate repeatability.
Repeatability shall meet the following requirements at the same time:
- The maximum value of CIEDE2000 is less than 1.0;
- The median value of CIEDE2000 is less than 0.4.
4.3 Light source box
4.3.1 General
The box shall meet the following requirements:
Annex A
(normative)
Grading of the degree of discoloration of the specimen
A.1 Principle
Measure the original specimen and the tested specimen. The test area is manually
selected by the operator or automatically selected by the software. Use CIEDE2000 to
calculate color difference. It is converted into a color-changing gray card level through
the formula.
A.2 Terms and definitions
A.2.1 original specimen
The reference sample for evaluating discoloration specified in GB/T 6151.
A.2.2 tested specimen
The specimen undergone the color fastness test.
A.2.3 uniform coloured area
The test area of the tested specimen is uniform in color.
NOTE: In this definition, the texture, gloss or other characteristics of the specimen that may affect
the visual effect of color can be ignored.
A.2.4 non-uniform coloured area
The test area of the tested specimen is not uniform in color.
NOTE: In this definition, the texture, gloss or other characteristics of the specimen that may affect
the visual effect of color can be ignored.
A.2.5 multi-coloured test specimen
Contain multiple colors within the test area of the specimen.
A.3 Instruments
Digital imaging devices shall be validated, calibrated or calibrated as described in
Chapter 4 and Annex C.
A.4 Specimen preparation
Annex B
(normative)
Evaluation of the degree of staining of the specimen
B.1 Principle
Measure original and post-tested linings. Calculate color difference according to
CIEDE2000. Convert it to a stained gray card grade through a calculation formula.
B.2 Instruments
Digital imaging devices shall be validated and calibrated as described in Chapter 4 and
Annex C.
B.3 Specimens
The original lining and the post-tested lining shall be fixed on white paper or card that
is visually uniform and free of fluorescence and opacity. Measure and store the data of
the original lining first. It is then compared to the test data of the post-tested lining. The
lining specimens within a calibration cycle shall be the same batch of standard lining
fabrics.
B.4 Procedures
B.4.1 Monochrome specimen
B.4.1.1 Measure the color of the original lining. For multifiber lining, the color of each
composition shall be measured separately. It is also possible to use the stored raw data
of standard lining. But it shall belong to the same batch of standard lining fabrics. Then
measure the color of the post-tested lining of the same composition.
B.4.1.2 For uniform coloured area, calculate the arithmetic mean. If the staining on the
lining is non-uniform, by mutual agreement, measure the areas with the most severe
color change. In this case, the areas with the most severe color changes are selected by
the "operator-selected area" (3.5) method, rather than all test areas. The use of this
method is noted in the report.
B.4.2 Multi-coloured test specimens
For each colour of the multi-coloured test specimen, repeat the test procedures for the
monochromatic specimen according to B.4.1. Test results for each color need to be
reported separately.
If the different colors of the specimen are stained with each other, then in accordance
Annex C
(normative)
Verification chart
C.1 Purpose
The verification chart is to convert the RGB value of the image captured by the digital
camera into the CIEXYZ value, so as to facilitate the measurement of the color of the
image.
C.2 Number of colors in verification chart
The verification chart shall be composed of at least 150 color blocks of different colors,
so as to ensure the measurement accuracy within the CIE color space.
C.3 Color reference measurement of verification chart
Use a spectrophotometer (diffuse: 8°, including specular component) to measure the
color of each color patch in the verification chart. The measuring instrument shall be
maintained at least once a year in accordance with the instructions of the instrument. Its
performance shall be checked by a series of reference materials. These reference
materials shall be certified and calibrated. The reflectance values are traceable to
national standards.
C.4 Measurement data of verification chart
The reflectance data of each color block is recorded and stored in the system software
as reference data for each camera calibration.
After each periodic maintenance of the instrument, or after using a new calibration color
card, new spectral data shall be replaced.
C.5 Requirements for verification chart
Before cutting each color block in the chart, its color shall be measured to ensure the
accuracy of chart verification.
The size of each color block shall meet the requirements of the measurement software
to measure each color. Generally, about 10mm×10mm is more suitable.
When installing the color block on the chart template, care shall be taken to avoid
contamination or damage to the surface color.
Each color block shall be separated by a black border. Adhere a layer of stencil to the
Annex D
(informative)
Summary of the international joint test report on the grading of color fastness to
digital imaging techniques
D.1 Introduction
The full detailed report has been submitted to ISO TC 38/SC 1 N2476. This appendix
is a brief summary of the report and conclusions.
D.2 Test range
The contents of the inter-laboratory test analysis are as follows:
a) Visual assessment:
- Differences between assessors;
- Differences between laboratories.
b) The effect of different calculation formulas for staining and discoloration.
c) Consistency between instruments.
D.3 Methods
D.3.1 Laboratories and assessors
This international inter-laboratory test consists of 7 laboratories, 17 assessors
(technicians): 3 each in laboratories in China, Korea, Sweden and France, 1 in a
laboratory in the US, 2 in each of the UK and German laboratories. However, it shall
be noted that after 3 Korean technicians perform visual assessment separately, the
average value is used only for analysis. Therefore, the data assessed by the other 14
individuals are all valid. In these tests, all assessors are trained and experienced in the
eye grading of colour fastness.
D.3.2 Samples
There are a total of 72 samples used for staining evaluation, 48 pairs of samples used
for discoloration evaluation. There are differences in lightness, chroma, hue or
comprehensiveness between dyed cloth samples. It can produce 72 color changing
samples. 8 sets of multifiber samples are stained. Different staining grades can be
produced for different fiber components. All samples are bound on visually uniform
white cards. They are identified with a unique number. Each laboratory grades the
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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