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CIE 186:2010 01-Feb-2010

CIE 186:2010

UV-A Protection and Sunscreens

Commission Internationale de L'Eclairage / 01-Feb-2010 / 56 pages
ISBN: 9783901906800

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Description

CIE Technical Committee TC 6-24 was formed in 1992 due to the importance of the deleterious effects associated with exposure to UV-A radiation and because of a lack of existing guidance/regulations on tests for UV-A protection. The objective was to arrive at an international consensus on such tests. By 1997 the committee had identified one in vivo method worth pursuing, i.e. Persistent Pigment Darkening, and several in vitro methods that had not yet been validated. It was not possible to reach a consensus at that time, however. In the meantime the development of methods to assess UV-A protection continued and is still on-going, especially on in vitro methods. Furthermore, the computer-aided calculation of sunscreen performance - referred to as in silico - became more sophisticated and useful. Rather than trying to find a consensus on sunscreen testing the objective of the reactivated TC 6-24 has now been reduced to giving, in the form of a Technical Report, a comprehensive overview as well as an assessment and ranking of the UV-A methods currently under discussion. This report starts with the general principles of UV protection and an overview of UV-A and broad-spectrum UV filters. Then a description and assessment of in vivo, ex vivo, in vitro and in silico methods is given. 

CIE 185:2009 01-Dec-2009

CIE 185:2009

Reappraisal of Colour Matching and Grassmann's Laws

Commission Internationale de L'Eclairage / 01-Dec-2009 / 20 pages
ISBN: 9783901906787

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The laws of additivity and proportionality of colour matches, Grassmann's laws, are the basis of all colour theory, but are not axiomatically true. The extent of departure of human vision from Grassmann's laws has been periodically examined. One exploration, by W. A. Thornton, found considerable failure of transformability of primaries - a symptom of Grassmann additivity failure. In the 14 years since Thornton's finding, several groups have formed to replicate and understand Thornton's results and the limitations of Grassmann's laws. CIE TC 1-56 is the latest of these. During the ten years of this committee's existence, statistical simulations indicated that replicate matches by the same observer (not present in Thornton's data) are required to suppress random errors, and accordingly three laboratories generated intra-observer matching results in three different luminance domains. Two of the studies, respectively conducted at 300 cd*m-2 and 30 cd*m-2, confirm Grassmann additivity, but the third study shows failure of additivity at 3 cd*m-2. In addition, Maxwell and maximum-saturation colour matches have long been known to be inconsistent even at high luminance levels and with intra-observer match replication to suppress noise. A practical consequence of the failure of additivity could be problems observed in crossmedia colour matching, although cross-media studies also have other well known sources of imprecision when the colour-matching is asymmetric. Some suggestions are made for a covering theory of Grassmann's laws that might accommodate both Maxwell and maximum-saturation match data while still maintaining consistency with high-luminance success in experiments such as reported recently. Further investigations are indicated for a successor to TC 1- 56.