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COMMISSION INTERNATIONALE DE L'ECLAIRAGE
INTERNATIONAL COMMISSION ON ILLUMINATION
INTERNATIONALE BELEUCHTUNGSKOMMISSION
CIE Central Bureau Kegelgasse 27 A-1030 Wien Austria
C O M M I S S I O N INTERNA TIO N ALE D E L’ECLAIRAGE-CIE
- CIE Technical Committee TC 5-23
R E P O R T O F T H E CIE TC 5-23 MEE T I N G O F 2 S E P T E M B E R 2008 I N HELSINKI - FINLAND
Present
Patrick Rombauts President TC (BE) Jacques Lecocq France
Kohji Kawakami Japan Tom Lemons USA
Petr Zak Czech Republic Marko Bizjak (Guest) (Slovenia) ?
Excused
John Rogers Australia
Murray Cronje South-Africa
José Luiz Pimenta Brasil
1. Welcome
This is the third meeting of this Technical Committee TC 5-23. Every present member or guest
has been cordially welcomed and invited for active participation in the committee work. The
attendee’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 this
Technical Committee : “To write guidelines for values of horizontal; vertical; semicylindrical;
hemispherical and spherical cap illuminances as well as of cubic
illumination for practical outdoor applications”. The new title of the TC is “Guidelines
for 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 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.
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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 ?
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Further important input came from Kohji Kawakami (JP) : A Japanese Industry Standard
on sports lighting is planned for publication in 2008 (the targets are e.g. the game balls and
the human faces) described by the space illumination characteristics ECyl and ESC (work on the
Standard has been started 7 years ago).
Axel Stockmar of Germany has published in the early 1980’s some papers on threedimensional
illuminances, the lighting field and cubic illumination where the accuracy of the
concepts and of the measurements is seriously put into question (see the lighting journals
“Lichtforschung” and “Lichttechnik”). These papers have to be studied thoroughly again
for implementation in the TC 5-23 document. In here, Axel Stockmar has proven that
approximating cubic illumination by means of 4 vertical illuminance values (from the
approximation formula of cubic illumination) is introducing very important errors (during that
period huge computer capabilities were not yet available). Counting the negative term in the
formula or not was not influencing the result; even when increasing the number of planes to
11 for instance.
Axel Stockmar has stated after this TC meeting that cubic illumination can better be directly
calculated without any problem, and not be estimated by very inaccurate measurements.
Axel Stockmar is questioning the validity of application of cubic illumination in outdoor
environments because of its nature as “general field”. Petr Zák replies on this by stating that
the outdoor lighting applications are no general field issues but on the contrary restricted
fields, with formulae even simplier. Petr Zák wishes to express his agreement on the
statement 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 Meeting
of 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” by
C. 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 integral
characterisation 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 lighting
field and cubic illumination have to be studied thoroughly again for implementation in
the TC 5-23 document.
� 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.
� Eduardo Manzano (ES; AR) will be contacted for eventual input.
CIE TC 5-23 Meeting Report 2_9_2008 Helsinki - Finland 4/6

CIE TC 5-23 Short Minutes Report on behalf of the CIE Division 5 Meeting September
3rd 2008, Helsinki
This TC held a meeting in Helsinki on September 2 nd 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 on
basis of these contributions and research that has been and will be carried out in Prague (Petr
Zák) and Brussels (Patrick Rombauts, VUB).
The next meeting will be held in Budapest, Hungary between early June 2009.
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