Abstract:Recently sky luminance distributions under fifteen ISO/CIE sky types were standardised in relative terms, i.e. all elementary sky luminance are normalised by the zenith luminance in nature. However, these standard sky luminance patterns can be characterised also in their physical units, see in CIE215:20014 which can be reduced by suitable intensity scales to simulate the very high natural sky luminance in laboratory under artificial sky domes. For the design of the electric illumination system of the artificial sky the appropriate zenith luminance for each sky type has to be derived respecting the indicatrix and gradation functions of each sky type. Thus, the sky patterns simulated in the artificial sky can be calibrated either by luminance measurements or by analysing fish-eye photos taken from the sky centre showing the smoothness and gradual changes of homogeneous sky type luminance patterns. The sky luminance images can be utilised to proceed with the adjustment or dimming of the LED electrical system to the final calibration check containing zenith luminance and exterior illuminance in the second calibration step.
References:1. Kittler, R. Slnko a svetlo v architektúre (Sun and light in architecture). Bratislava: SVTL, 1956. 2. Darula, S., Kittler, R. A methodology for designing and calibrating an artificial sky to simulate ISO/CIE Sky Types with an artificial sun// Leukos, 2015, V11, pp. 93–105. 3. Darula, S., Kittler, R. The new generation of an artificial sky: simulating various overcast sky conditions// Proc. of the European Lighting Conference Lux Europa 2017. Ljubljana: Lighting Engineering Society of Slovenia, 2017, pp. 401–405. 4. Lambert, J.H. Photometria sive de mensura et gradibus luminis, colorum et umbrae (1760) (Photomery for measuring and grading light, colour and shades). Augsburg: Detlefsen. (German translation by E. Anding: Lamberts Fotometrie. Leipzig: Klett Publ., 1892. English translation by D.L. DiLaura: Photometry, or on the measure and gradation of light, colors and shade. New York: Publ.IES Amer., 2001). 5. Commission Internationale de l´Éclairage,1955, CIE-E3.2 Official recommendation: Natural daylight. Proc. Paris: CIE, II, 3.1. 6. Commission Internationale de l´Éclairage, Technical Report 22 Standardisation of luminance distribution on clear skies, Paris, 1973, CIE Central Bureau. 7. Commission Internationale de l´Éclairage, CIE Standard Spatial distribution of daylight – CIE Standard of General Sky, 2003 CIE Standard S011/E: 2003. Vienna: CIE Central Bureau. 8. International Standard Organisation: ISO Standard 15409:2004 Spatial distribution of daylight – CIE Standard of General Sky. Geneva: ISO, 2004. 9. Kittler, R. and Darula, S. The simultaneous occurrence and relationship of sunlight and skylight under ISO/CIE standard sky types// Lighting Research Technology, 2015, V47, pp. 565–580. 10. Roy, G., Kittler, R., Darula, S. An implementation of the Method of Aperture Meridians for the ISO/CIE Standard General Sky// Lighting Research Technology, 2007, V39, #3, pp. 253–264. 11. Kittler, R., Kocifaj, M., Darula, S. Daylight Science and Daylighting Technology. New York: Springer, 2012. 12. Komar, L. Calibration of the artificial sky using fisheye images. Proc. of the VI. IEEE Lighting Conference of the Visegrad Countries LUMEN V4, 2016, pp. 242–245. 13. Baxant, P. Common digital photography and its calibration to luminance measurement. Proc. of the European Lighting Conference Lux Europa 2005, Berlin. Berlin: Deutsche Lichttechnische Gesellschaft e.V., 2005, pp. 318–321. 14. Kobav, M., B. Uporaba digitalnega fotoaparata s širokokotnim objektivom v funciji merilnika porazdeletve scetlosti neba (Using a digital camera with a wide-angle lens in the function of the sky luminance distribution meter). Proc. Conference Razsvetljava 2006, Bled. Maribor: Lighting Engineering Society of Slovenia, pp. 167–178. 15. Škoda, J. (2014). Kalibrační protokol k přístroji Nikon D80 s fisheye objektivem, č. 11/2004-SAV (Protocol of the calibration Nikon D80 with fisheye lens No. 11/2004-SAV), Laboratoř světelné techniky, Brno: VUT, 2004. 16. Tregenza, P. Subdivision pf the sky hemisphere for luminance measurements. Lighting// Research Technology, 1987, #1, pp. 13–14. 17. Darula, S., Kittler, R. New trends in daylight theory based on the new ISO/CIE Sky Standard. 1. Zenith luminance on the overcast skies// Building Research Journal, 2004, V52, #3, pp. 181–197.
Review of the Current State and Future Development in Standardizing Natural Lighting in Interiors. L&E 26 (4) 2018