The New Method To Calibrate Iso/cie General Skies modelled In Artificial Skies

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.