ASTM E1347 Color-Difference Measurement by Tristimulus Colorimetry

Scope:

Instrumental measurement with colorimeters or spectrophotometers with either hemispherical or bidirectional optical measuring equipment is the most direct and accessible approach for determining the color differences and color coordinates of object colors. Color differences of non metameric, nonparametric pairs of objects, color specimens, or color coordinates of most such specimens, can be measured using this ASTM E1347 test method. 

Procedure:

For the ASTM E1347 test, color scales were selected, observed, and illuminated for the computation of color coordinates, as well as the inclusion or absence of the specular component of reflection. The specimen is placed against the integrating sphere’s reflectance measuring port, using supporting material. Placed the specimen flush against the integrating sphere’s transmission measuring port for total luminous quantities. The specimen is placed in the transmission compartment, flush against the integrating sphere’s transmission measurement port, to measure translucent specimens. When specimens have directionality and a uniplanar instrument is utilized, information on directionality is retrieved by measuring the specimens at multiple rotation angles, usually two 90° angles apart. Following the manufacturer’s instructions, the specimen is measured.

Video 01: Measuring color difference by a colorimeter

Specimen size:

The specimens used in ASTM E1347 testing are opaque specimens with at least one plane surface; translucent and transparent specimens with two essentially plane and parallel surfaces and a standard thickness.

Data:

When measuring directionality in specimens using instruments with uniplanar geometry at two or more rotation angles, average the instrumental data for all rotation angles observed.

Conclusion:

When color coordinates are required, this ASTM E1347 test technique demands that the instrument be standardized by using a standard with similar spectral (color) and geometric features to the specimen. A product standard is another name for this standard. It is highly beneficial to use a product standard that is stable.