Paper published in LEUKOS

Spectrally and spatially resolved information on daylight is critically important when planning for non-image forming (NIF) responses. Nevertheless, the availability of such data is scarce given the high initial costs and complex on-site maintenance of high-end spectral measurement devices. The CIE (Commission Internationale de l’Éclairage) reconstruction procedure allows for the derivation of the daylight spectral power distribution (SPD) from the chromaticity coordinates or the correlated color temperature.
 
Our open access paper published in LEUKOS studies the reconstruction accuracy of the SPD of daylight, and contextualizes the findings in relation to NIF effects.
 
The results indicated that a localized procedure, adjusting both the daylight locus and the PCA components of daylight, outperformed the CIE reconstruction method. However, improvement in the reconstruction accuracy had no effect on NIF assessment. The RSMPE for α-opic quantities did not exceed 4% for any
procedure. In practical terms, this implies that cost-effective sensors and the representation of spectral properties in sky models with a single value – the correlated color temperature – can be used for NIF purposes.
 
Highlights
• Using a localized procedure to define spectral power distribution (SPD) based on correlated color temperature (CCT) outperforms the CIE method.
• Accuracy depends on the computation procedure rather than the daylight locus location.
• Higher accuracy does not affect the α-opic responses used in defining non-image forming (NIF) effects.
• Findings confirm the applicability of simplified measuring and representation methods for daylight SPDs.
• CCT can be used to represent daylight SPD in planning software to assess NIF effects.

You can find our paper here

co-authored with: Martine Knoop-Velds and Nils Weber 

This research was supported by the Velux Stiftung