ASTM E1348 Transmittance and Color by Spectrophotometry Using Hemispherical Geometry
ASTM E1348 explains the use of a spectrophotometer or spectrocolorimeter with a hemispherical optical measuring apparatus, such as an integrating sphere, to measure the transmission characteristics and color of object-color specimens. The value stated in SI is considered as standard.
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- Overview
- Scope, Applications, and Benefits
- Test Process
- Specifications
- Instrumentation
- Results and Deliverables
Overview
ASTM E1348 is the standard test method for quantifying the transmittance and color of object-color specimens utilizing a spectrophotometer equipped with a hemispherical optical system, such as an integrating sphere. This method enables accurate measurement of light transmission and coloration in translucent materials, yielding data for color coordinates, including CIE L*a*b*, applicable across diverse industries.
Scope, Applications, and Benefits
Scope
Instrumental measurement with spectrophotometers or colorimeters using hemispherical or bidirectional optical measurement systems is the most direct and accessible approach to acquiring the color coordinates of object colors. This ASTM E1348 test method is particularly well-suited for measuring specimens that are completely translucent or hazy, and it is acceptable if they can be positioned flat against the integrating sphere’s transmission port.
Applications
- Plastics, polymers, glass, and optical films – assessing clarity and color.
- Manufacturing QC and incoming material inspection.
- Product R&D – evaluating material formulation or thickness changes.
- Color matching in automotive, consumer goods, and coatings.
- Scientific research – obtaining quantitative optical data.
Benefits
- Provides accurate, repeatable measurements of color and transmittance.
- Suitable for transparent and translucent materials.
- Reduces subjectivity with instrument-based spectral measurements.
- Internationally recognized, enabling cross-lab comparability.
- Supports quality control, compliance, and material verification
Testing Process
Instrument Setup
Use a calibrated spectrophotometer equipped with an integrating sphere for transmission measurements.
1Instrument Calibration
Perform wavelength and photometric calibration using defined reference standards as specified by the instrument manufacturer.
2Selection of Measurement Conditions
Select the required illuminant, standard observer, wavelength range, and measurement interval based on the test requirement.
3Data Recording & Reporting
Report transmittance values, color data, instrument settings, and test conditions, including any deviations from the standard.
4Technical Specifications
| Parameter | Details |
|---|---|
| Optical Geometry | Hemispherical (integrating sphere) transmission |
| Applicable Materials | Transparent and translucent solid materials |
| Wavelength Range | Visible spectrum (typically 380–780 nm) |
| Observer Angle | Standard observer (2° or 10°) |
| Specimen Placement | At the transmission port of the integrating sphere |
| Instrument Type | Spectrophotometer or Spectrocolorimeter |
| Reporting Requirements | Instrument settings, measurement conditions, and results |
Instrumentation Used
- UV–Vis spectrophotometer
- Integrating sphere (hemispherical geometry)
- Calibrated color and transmittance standards
- Sample holder or mounting stage
- Stable light source
- Data acquisition and color analysis software
Results and Deliverables
- ASTM E1348 defines a spectrophotometric method for measuring the transmittance of transmitting specimens.
- The method is suitable for fully transparent specimens, regardless of their position relative to the instrument’s transmission port.
- Translucent specimens must be positioned flush against the integrating sphere’s transmission port to ensure accurate measurements.
- Proper specimen positioning ensures capture of both direct and diffuse transmitted light.
Frequently Asked Questions
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