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4. Discussion of the Draft Report version 3 This document is an intermediate document in view of a new core document that covers better the new terms of reference. Jacques Lecocq will send a English text “Illuminances on 3D point surfaces and visual perception” to be incorporated in the CIE document §4.7. J. Lecocq is working on the model of visibility of Werner Adrian for road lighting. He also wants to state that semi-cylindrical and cylindrical illuminances are no good characterising parameters here. In the future we will take more and more pictures and so we ought to speak of luminances; and from there we are able to simulate the spreading of luminances, which was not possible up to now ! We should apply this in all lighting issues and even for the oncoming driver in road lighting. Eventually, there could be a liaison set up with CIE TC 4-36 and take also into account glare, the road surface and the oncoming driver with his/her headlights. We never take into account specular surfaces in the calculation for a ping-pong ball f.i. as it is considered matt. Measurements on the contrary are eventually carried out with specular surfaces. This represents a secondary issue. The objects are sometimes flat, but they are moving; observers are moving too as with swimming. Vertical illuminance is neither a good parameter, it has no capacity with illumination. Eventually simplifying the issue by considering flat objects is associated with too much lighting in the proximity of the light source. Glare is also more important in certain directions. With visibility, luminance is the concept to apply, together with colour because of high illuminance levels. E. g. with flat objects, at 1200 lux, there is need to overrating the lighting installation; one should preferably take then curved objects and the concept of illuminance on spherical cap. J. Lecocq wants to mention that the global uniformity is around 0,6 and that the luminance gradient on the object has not yet been studied; anyway the luminance contrast is a useful concept. The background is considered more or less uniform and if the object luminance is equal to the background luminance then the object is invisible as in road lighting. J. Lecocq is seriously questioning the concept of hemispherical illuminance for the detection of objects on the ground and one should merely use two-dimensional illuminance normal to the camera - or according to another well-defined direction - as the concept (and not purely “vertical” illuminance). J. Lecocq has created a “real lux meter” that is able to measure hemispherical and spherical cap illuminances depending on the viewing direction (notwithstanding Axel Stockmar's thesis – see the paragraph at the end of this report); as measurements are needed in any case to verify and to validate the calculations and to numerically define the concept of spherical cap illuminance. Petr Zák replies that cubic illumination is concerning 6 surfaces and there is indeed lack of a concept that is able to calculate the back of an object and J. Lecocq is adding that we should treat light as a “vector” with varying directions. Petr Zák would like to stress the fact that illuminance concepts are not direction related of which J. Lecocq states that even horizontal or vertical illuminances are direction related anyway. Both agree with the luminance concept as calculation mode which is explicitly direction related. Petr Zák wishes to conclude provisionally in a sense that the way (i.e. the geometrical distribution and the intensity) light is falling on an object is very important too; and that the shape of an object is not determined by the illuminance distribution but by the luminance distribution and colour. We are able to take photographs with a luminance and colour sensitive film but we can not calculate the proper visibility yet today. Kohji Kawakami will send by spring 2009 another text “Recommendation for Sports Lighting _JIS Draft 1” evenly to be implemented in the document on the subject of recognition of faces and objects in sports lighting. CIE TC 5-23 Meeting Report 2_9_2008 Helsinki - Finland 2/6
Tom Lemons wants to put forward that there exists a difference between the recognition of faces and that of a tennis ball or baseball as an example; it is in fact more than pure threedimensional appearance : is the ball spinning or not; where is the ball, as the ball can be everywhere ? Also, the backlight is very important. Tom Lemons wants to see a range of illuminances (values) for the user presented in this document. Tom Lemons would like to bring forward describing/defining the illuminance concepts that are used in Denmark and Japan and simplify this as no real guidelines are expected. He shall study the CIE Vocabulary and copy the definitions. The DIN-norm is a reference too. P. Rombauts replies that we shall rely upon existing research and take these references where the calculations have been done or can be done. He wants to add cubic illumination apart from the already defined concepts of semi-cylindrical, cylindrical, hemispherical and spherical cap illuminances. The extra content of “cubic illumination” could be borrowed from Kit Cuttle. Tom Lemons will prepare a text on “cubic illumination” and send the proposal to Kit Cuttle for approval. Petr Zák would like to mention that no further research has been carried out during the last year and he wants to propose an explicit linking of the illuminance values with matching, corresponding lighting applications. Tom Lemons replies that no new research is needed and that we should stick to the existing research and link it with the applications, including fill and backlight and TV. The scope and the terms of reference are expanded to the “general characterisation of the lighting field”. Members and guests are asked by the chairman for input, i.e. theoretical and experimental work where can be referred to or that has been carried out for all types of illuminances, in particular cubic illumination. Major input came from Petr Zák (Czech Republic) with a paper (in Czech) on calculations and measurements of cubic illumination and the light vector; further cooperation is planned between Petr Zák and P. Rombauts (VUB) for research and master thesis work. Cubic illumination has been calculated and measured in a general field, compared to all other types of illuminances, like the E4p (spherical illuminance in a control point). Petr Zák’s research has finished at this point for now. Measurements are carried out via a 6 sided standard illuminance meter (cubic illumination and spherical illuminance); a 5 sided standard illuminance meter (hemispherical illuminance); a 4 sided standard illuminance meter (semi-cylindrical illuminance). Petr Zák states that with outdoor lighting applications, the field can be restricted and the relation will be simplier. Petr Zák has done some measurements to compare spherical with semi-cylindrical illuminances and he will look for this application to send the corresponding details to the TC chairman. Students of the Czech Praha University could carry out this work together with and under the responsability of Petr Zák. P. Rombauts asked himself if measurement comparison campaigns have been carried out between vertical, horizontal, semi-cylindrical, hemispherical and spherical cap illuminances and cubic illumination. Jacques Lecocq (FR) must have done so for sports lighting ? P. Rombauts refers to the work of Kohji Kawakami (JP) where a correlation between the face’s luminance and the face’s (vertical and semi-cylindrical) illuminance is showed. A Work Scheme will be established by P. Rombauts to meet the new terms of reference and to solve the issue of people face’s brightness, characterised by illuminance parameters, by setting up a student’s Master thesis project. The project will cover both calculations and experiments. Kohji Kawakami’s work will be of great help here. P. Rombauts is asking himself what types of outdoor lighting applications should be covered (sports, urban, pedestrian, …) ? And, with all the types of illuminances ? CIE TC 5-23 Meeting Report 2_9_2008 Helsinki - Finland 3/6
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