Apparatus for providing ultra-accelerated natural sunlight exposure testing of samples under controlled weathering without introducing unrealistic degradation mechanisms in exposed materials and without breaking reciprocity relationships between flux exposure levels and cumulative dose that includes single or multiple concurrent levels of temperature and/or relative humidity at high levels of natural sunlight comprising: a) means for concentrating solar flux uniformly as concentrated uniform reflected or refracted light; b) means for achieving spectral splitting prior to directing the UV/VIS portion of the spectrum into the sample exposure chamber; and c) means for directing said controlled uniform reflected or refracted light onto sample materials in a chamber enclosure having single or multiple concurrent levels of temperature and/or relative humidity to allow the sample materials to be subjected to accelerated irradiance exposure factors for a sufficient period of time in days to provide a corresponding time of about at least a years worth of representative weathering of said sample materials.
