does not stop at 380 nm though, and all radiation (UV, visible, IR) has the potential to damage art. Thus, calculating a simple average of all wavelengths between 300 nm and 380 nm does not account for the fact that different wavelengths have different artwork damage potential. At least two other methods exist, which provide a more holistic measurement of radiation damage, from both the UV and visible portions of the spectrum: Krochmann Damage Function (KDF) is used to rate a glazing's ability to limit fading potential. It expresses the percentage of both UV and of that portion of the visible spectrum from 300 nm to 600 nm that passes through the window and weights each wavelength in relation to the potential damage it can cause to typical materials. Lower numbers are better. ISO-CIE Damage-Weighted Transmission (ISO) uses a weighting function recommended by the International Commission on Illumination (CIE). Its spectral range is also weighted and extends from 300 nm to 700 nm. For picture framing purposes, it is not appropriate to use these methods for absolute ratings, since "Better" ratings are obtained with lower visible light transmission, which is not aesthetically desirable in a framing glazing. However, by including more art damaging factors than UV radiation between 300 nm and 380 nm, these methods provide a more holistic relative ranking tool. For example, comparing a 99% and 92% UV Blocking glazing, would translate to 44% and 41%, respectively, under the KDF. How much UV filtering should a glazing have The discussion on how much UV filtering is necessary in art framing is complex and controversial, driven by conflicting corporate interests. There have so far been no independent organizations, not tied to corporate sponsors, which have presented scientifically verifiable and conclusive evidence to the amount of UV filtering necessary for a glazing to both display and at the same time protect an artwork. On one hand, the issue is complicated by the varying amount of damaging light actually present in an indoor environment (from low level indirect sources to direct daylight). On the other, by the fact that not only UV, but also visible light damages an artwork. According to the National Fenestration Rating Council, only 40% of artwork fading is caused by UV radiation. The remaining damage comes from the visible light, heat, humidity and material chemistry. This means that increasing visible light transmission by an anti-reflective coating actually