Lighting : LIGHTING Jun-July 2018
20 LIGHTING MAGAZINE | June/July 2018 ©2018 Soraa, Inc. The synthesis of perfect light and inspired design. With the introduction of Soraa ArcTM, stunning form follows remarkable function in luminaires endowed with Soraa’s signature quality of light, featuring rich colours, perfectly rendered whites, and clean, crisp beams. Proudly distributed by Lighting Options Australia. www.lightingoptionsaustralia.com.au To compare the luminance or reflectance of the different colours (Figure 4) was considered but to use a standard instrument that would have an inbuilt V(λ) filter would introduce a further problem. This obstacle was overcome by converting the images into black and white images and measuring the luminance of each of the samples. The results are shown in Table 1. Note that a correction of the values for the V(λ) measurements had to be made because the daylight illuminance was not the same for both photographs. A comparison of the luminance values shows that the ratio between the values for different colours varies from 1.42 for yellow to 2.38 for blue depending on the individual colour. This means that using the V(λ) approach distorts the measurement of a lamp’s SPD and would affect the lamp efficacy. In addition, depending and on the colour performance measurement approach, it can affect the colour appearance and colour rendering classification. WHERE NEXT? Clearly this pilot experiment has limitations and the issue needs much more consideration. We need to have a better understanding of the colour response of human sight to enable electric light sources to be developed that provide the quality of colour performance, both colour rendering and colour appearance, on the basis of accurate measurement values. Recently Mark Rea has suggested a U(λ) SPD which embraces all the SPDs for the known vision receptors contained within the human eye. Perhaps a better solution would be to use a ‘smoothed’ daylight envelope covering the human spectral range 400–700 nm (see Figure 5). It covers all of the human visual spectral range, not equally but very similar to daylight. After all it is common practice for people to use natural daylight when trying to accurately assess colour samples or colour matches. Figure 4. The array of colour samples from Figure 3 labelled. The measurements were carried out by averaging the luminance over a small patch on each sample. Figure 3. Photographs of the arrangement of coloured samples (socks): uppermost, under daylight and lower, under daylight with V(λ) filter.
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