COMMISSION INTERNATIONALE DE L'ECLAIRAGEINTERNATIONAL COMMISSION ON ILLUMINATIONINTERNATIONALE BELEUCHTUNGSKOMMISSION

CIE Central Bureau Kegelgasse 27 A-1030 Wien Austria

COMMIS S ION INTER NAT IONA LE DE L ’EC LA IRA G E-CIE- CIE Technical Committee TC 5-23

REP ORT OF TH E CIE TC 5-23 MEE TING OF 2 SEP TEMBER 2008 IN HEL S INKI - FINL A ND

PresentPatrick Rombauts President TC (BE) Jacques Lecocq FranceKohji Kawakami Japan Tom Lemons USAPetr Zak Czech Republic Marko Bizjak (Guest) (Slovenia) ?

ExcusedJohn Rogers AustraliaMurray Cronje South-AfricaJosé Luiz Pimenta Brasil

1. Welcome

This is the third meeting of this Technical Committee TC 5-23. Every present member or guesthas been cordially welcomed and invited for active participation in the committee work. Theattendee’s list is attached.

2. Terms of Reference of this TC

The president would like to remind the participants of the modified terms of reference of thisTechnical Committee : “To write guidelines for values of horizontal; vertical; semi-cylindrical; hemispherical and spherical cap illuminances as well as of cubicillumination for practical outdoor applications”. The new title of the TC is “Guidelinesfor the use of different Illuminance parameters in Outdoor Applications”.

3. Approval of the Report of the Meeting in Beijing – China (10 July 2007)

The report of the meeting was approved without further remarks.

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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 betterthe new terms of reference.

Jacques Lecocq will send a English text “Illuminances on 3D point surfaces and visualperception” 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 alsowants to state that semi-cylindrical and cylindrical illuminances are no good characterisingparameters here. In the future we will take more and more pictures and so we ought to speakof luminances; and from there we are able to simulate the spreading of luminances, which wasnot possible up to now ! We should apply this in all lighting issues and even for the oncomingdriver in road lighting. Eventually, there could be a liaison set up with CIE TC 4-36 and takealso 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 isconsidered matt. Measurements on the contrary are eventually carried out with specularsurfaces. This represents a secondary issue. The objects are sometimes flat, but they are moving; observers are moving too as withswimming. 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 lightingin the proximity of the light source. Glare is also more important in certain directions. With visibility, luminance is the concept toapply, together with colour because of high illuminance levels. E. g. with flat objects, at 1200lux, there is need to overrating the lighting installation; one should preferably take thencurved 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 luminancegradient on the object has not yet been studied; anyway the luminance contrast is a usefulconcept. The background is considered more or less uniform and if the object luminance isequal 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 ofobjects on the ground and one should merely use two-dimensional illuminance normal to thecamera - 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 sphericalcap 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 toverify and to validate the calculations and to numerically define the concept of spherical capilluminance. Petr Zák replies that cubic illumination is concerning 6 surfaces and there isindeed lack of a concept that is able to calculate the back of an object and J. Lecocq is addingthat we should treat light as a “vector” with varying directions. Petr Zák would like to stressthe fact that illuminance concepts are not direction related of which J. Lecocq states that evenhorizontal or vertical illuminances are direction related anyway. Both agree with theluminance concept as calculation mode which is explicitly direction related. Petr Zák wishes to conclude provisionally in a sense that the way (i.e. the geometricaldistribution and the intensity) light is falling on an object is very important too; and that theshape of an object is not determined by the illuminance distribution but by the luminancedistribution and colour. We are able to take photographs with a luminance and colour sensitivefilm 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 facesand objects in sports lighting.

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Tom Lemons wants to put forward that there exists a difference between the recognition offaces and that of a tennis ball or baseball as an example; it is in fact more than pure three-dimensional appearance : is the ball spinning or not; where is the ball, as the ball can beeverywhere ? Also, the backlight is very important.Tom Lemons wants to see a range of illuminances (values) for the user presented in thisdocument. Tom Lemons would like to bring forward describing/defining the illuminance concepts that areused in Denmark and Japan and simplify this as no real guidelines are expected. He shallstudy 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 wherethe 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 “cubicillumination” could be borrowed from Kit Cuttle. Tom Lemons will prepare a text on “cubic illumination” and send the proposal to Kit Cuttle forapproval.

Petr Zák would like to mention that no further research has been carried out during the lastyear 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 andthat we should stick to the existing research and link it with the applications, including fill andbacklight and TV.

The scope and the terms of reference are expanded to the “general characterisation of thelighting field”.

Members and guests are asked by the chairman for input, i.e. theoretical and experimentalwork where can be referred to or that has been carried out for all types of illuminances, inparticular cubic illumination.

Major input came from Petr Zák (Czech Republic) with a paper (in Czech) on calculations andmeasurements of cubic illumination and the light vector; further cooperation is plannedbetween Petr Zák and P. Rombauts (VUB) for research and master thesis work. Cubicillumination has been calculated and measured in a general field, compared to all other typesof illuminances, like the E4p (spherical illuminance in a control point). Petr Zák’s research hasfinished at this point for now. Measurements are carried out via a 6 sided standard illuminance meter (cubic illumination andspherical illuminance); a 5 sided standard illuminance meter (hemispherical illuminance); a 4sided standard illuminance meter (semi-cylindrical illuminance). Petr Zák states that withoutdoor lighting applications, the field can be restricted and the relation will be simplier. Petr Zák has done some measurements to compare spherical with semi-cylindricalilluminances and he will look for this application to send the corresponding details to the TCchairman. Students of the Czech Praha University could carry out this work together with andunder the responsability of Petr Zák.

P. Rombauts asked himself if measurement comparison campaigns have been carried outbetween vertical, horizontal, semi-cylindrical, hemispherical and spherical cap illuminancesand 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 theface’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 tosolve the issue of people face’s brightness, characterised by illuminance parameters, bysetting up a student’s Master thesis project. The project will cover both calculations andexperiments. 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 ?

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Further important input came from Kohji Kawakami (JP) : A Japanese Industry Standardon sports lighting is planned for publication in 2008 (the targets are e.g. the game balls andthe human faces) described by the space illumination characteristics ECyl and ESC (work on theStandard has been started 7 years ago).

Axel Stockmar of Germany has published in the early 1980’s some papers on three-dimensional illuminances, the lighting field and cubic illumination where the accuracy of theconcepts and of the measurements is seriously put into question (see the lighting journals“Lichtforschung” and “Lichttechnik”). These papers have to be studied thoroughly againfor implementation in the TC 5-23 document. In here, Axel Stockmar has proven thatapproximating cubic illumination by means of 4 vertical illuminance values (from theapproximation formula of cubic illumination) is introducing very important errors (during thatperiod huge computer capabilities were not yet available). Counting the negative term in theformula or not was not influencing the result; even when increasing the number of planes to11 for instance. Axel Stockmar has stated after this TC meeting that cubic illumination can better be directlycalculated without any problem, and not be estimated by very inaccurate measurements.

Axel Stockmar is questioning the validity of application of cubic illumination in outdoorenvironments because of its nature as “general field”. Petr Zák replies on this by stating thatthe outdoor lighting applications are no general field issues but on the contrary restrictedfields, with formulae even simplier. Petr Zák wishes to express his agreement on thestatement of poor accuracy of the cubic illumination measurements.

5. Next meeting

The next meeting will be held in Budapest_Hungary on the occasion of the Midterm Meetingof the CIE Divisions 4 & 5 between 1 and 3 June 2009.

6. Activities to be carried out

C. Cuttle could be invited for the next meeting.

Tom Lemons will send a photocopy of the chapter of the book “Cubic Illumination” byC. Cuttle to P. Rombauts. Tom Lemons will also prepare a text on “Cubic Illumination”and send the proposal to Kit Cuttle for approval.

Petr Zák (Czech Republic) will translate his paper of 1999 on the integralcharacterisation of the lighting field from Czech to English.

The papers that Axel Stockmar of Germany has published in the early 1980’s in“Lichtforschung” and “Lichttechnik” on three-dimensional illuminances, the lightingfield and cubic illumination have to be studied thoroughly again for implementation inthe TC 5-23 document.

A Work Scheme will be established by P. Rombauts to meet the new terms of referenceand to solve the issue of people face’s brightness, characterised by illuminanceparameters, by setting up a student’s Master thesis project.

Eduardo Manzano (ES; AR) will be contacted for eventual input.

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CIE TC 5-23 Short Minutes Report on behalf of the CIE Division 5 Meeting September3rd 2008, Helsinki

This TC held a meeting in Helsinki on September 2nd 2008.

Six people, among five members, attended the meeting and took part in the discussion.

Interesting and substantial contributions came from Jacques Lecocq (FR), Tom Lemons (USA),Petr Zák (Czech Republic) and Kohji Kawakami (Japan).

Because of the modified terms of reference, the third draft will be completely rewritten onbasis of these contributions and research that has been and will be carried out in Prague (PetrZák) and Brussels (Patrick Rombauts, VUB).

The next meeting will be held in Budapest, Hungary between early June 2009.

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