Micom offers test services to ASTM D2244 – Standard Test Method for Calculation of Color Differences from Instrumentally Measured Color Coordinates. The sample color is measured and the results can be expressed on the L, a, b or x, y, z scales. This test method is often used in conjunction with accelerated aging test methods for UV testing per ASTM G155, ASTM G154, ASTM F1515 and many others.
Color measurements are often required with other appearance factors such as gloss – ASTM D523, haze, distinctness of image (DOI) and reflected image quality. Indeed the sample texture, may affect the correlation between the magnitude of a measured color difference and its commercial acceptability.
Use and factors to be considered:
The color difference between a reference and an aged test specimen, as measured using ASTM D2244, are determined using a colorimeter. Typically two color scales are used for color measurement: tristimulus X, Y, Z or the L, a, b scale. Color differences among specimens should be compared only when they were measured on the same color scale system.
A simplified approach for gaging color shifts uses “Delta E”:
Generally speaking the human eye can perceive a Delta “E” greater of equal to 2,3. However, for quality control purposes, it is necessary to know not only the magnitude of the departure from standard but also the direction of this departure. Information on the direction of a color difference is easily included by giving the three instrumentally determined components of the color difference.
Typical Experimental parameters:
ASTM D2244 method does not cover preparation techniques. However, generally speaking, samples should be clean, dry and free of deposits. Minimally we need a flat, homogeneous area, the size of a nickel.
Other test methods related to ASTM D2244:
We also invite you to download our PDF on the true color measurement: What is the difference between the “true” color of an item and its “perceived” color (by the human eye)?
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