CIE x018-1999

The 1999 Symposium of the CIE was held at the Hungarian Academy of Sciences, Budapest, between 30 September and 2 October 1999, celebrating the 75th anniversary of the CIE photometric system. Papers dealt with the present photometric system, and discussed its shortcomings and possible extensions.

The presented papers and discussions made it clear that the 75 year old photometric system is still the internationally accepted basis for all visually significant light measurements. It defines one of the base units of the SI system, the candela, and as such it should have a permanent status also in the future. Contributions pointed out, however, that since 1924 great progress has been achieved that found only partly its way into CIE recommendations and standards. By now it is clear that one has to differentiate between foveal vision photometry, to be used when it is important to see and recognise small details, and a photometry that can help illuminating engineers to describe parafoveal vision, brightness perception in the lit environment and mesopic vision.

An introduction was presented by Dr. Hengstberger, at the time of starting the organization of the meeting Director of CIE Division 2 and now Vice President for Publications. Highlights of the meeting were: Professor Valberg, one of the leading scientists in vision research, described underlying vision research that makes the difference between flicker photometry based V(lambda) and opponent colour channel influenced brightness perception understandable. Dr. McGowan’s paper discussed the application of photometry in lamp industry. Prof. Rea dealt with the applicability of V(lambda) based photometry for foveal recognition of tasks, also in the mesopic range, and possible extensions for parafoveal vision, where at mesopic levels a photometry based on a 10 degree observer with rod participation seems to be necessary. Photometry is important in interior design, this question and some of the necessary extensions of the present photometric system to cope with the requests interior designers have were dealt with by Prof. Loe. Papers by Dr. Blevin and Dr. Wallard explained the interaction between CIE and the Meter Convention and how new scientific results could find their way into the system of international units and measures. Dr. Walraven reported on the progress CIE TC 1-36 made to recommend a fundamental chromaticity diagram, and to provide data for the extension of the V(lambda) function into the infrared. Dr. Sagawa, Director of CIE Division 1 showed in his closing paper the vision of a future photometer, which is an image photometer, where you can switch among a number of evaluation functions, depending on the actual task to be checked.