Reflectance Testing

Solar Light’s Materials Testing Lab offers a variety of Reflectance Tests.

With our Visible Light Reflectance Test service, we may use any number of color coordinate systems, the primary being the CIE L*a*b* system.
The L * value indicates the Level of Light- Dark.  (0  – 100)
the a* value Redness or Greenness   (-100 = Green; +1-00 = Red)
the b* value Yellowness or Blueness (-100) = Blue; +100 = Yellow)

The two measures calculated are:

1) DELTA E which is obtained by the formula
√((L*-L*)² + (a*-a*0)² +(b*-b*0)²)           (1)
The Delta E value merges the overall color change into a parameter that provides a single overall value of change from the baseline.

Where L*, a* and b* are the CIE colorimetric parameters such that the L * value indicates the Level of Light- Dark, the a* value Redness or Greenness, and the b* value Yellowness or Blueness.

The delta E is always positive (or zero) and a value less than 2.0 is generally considered as a change of color that is less than what the human eye can distinguish.

2)  The Yellowness Index    YE313 (per ASTM E313)
The Yellowness Index (ASTM E313) characterizes the amount of “Yellowing” on a scale of -100 (saturated blue to +100 saturated yellow).

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  • Visible Light Reflectance Test

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    Solar Light Company, Inc. provides Visible Spectral Reflectance Testing Services, covering the 400-700nm range with 10nm intervals. As a means of assessing the changes of a material under the action of accelerated light exposure, we employ our Hunter spectrophotometer to measure the Spectral Reflectance, or color changes.


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