In the daylight reflectance test, the specular daylight reflectance is calculated as:
Specular daylight reflectance = Total daylight reflectance – Diffuse daylight reflectance
Due to the rounding operations, the reported specular specular daylight reflectance could be:
Specular daylight reflectance = Total daylight reflectance – Diffuse daylight reflectance ± 0.001
Shown below is an example result set, with this ± 0.001 discrepancy:
- Total daylight reflectance = 0.216 (21.6%)
- Diffuse daylight reflectance = 0.200 (20.0%)
- Specular daylight reflectance = 0.015 (1.5%)
Some customers expect that the specular daylight reflectance should be 0.216 – 0.200 = 0.016 (1.6%) and suspect that there is a typo in the test report.
Our daylight reflectance test reports are generated by in-house software automatically. The ±0.001 discrepancy is not due to a calculation mistake or a typo, but due to the rounding operations, as illustrated in the table below:
| Before rounding | After rounding | |
|---|---|---|
| Total daylight reflectance | 0.2156 | 0.216 (21.6%) |
| Diffuse daylight reflectance | 0.2004 | 0.200 (20.0%) |
| Specular daylight reflectance | 0.0152 | 0.015 (1.5%) |