Minutes of the meeting

1. Opening of the meeting

Liisa Halonen opened the meeting and welcomed all to the 5 th meeting of TC1-58.

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2. Noting the TC members and introducing the participants

A list of the current TC members was reviewed. The participants introduced themselves.

3. Apologies for absence

Apologies for absence had been received from: Colette Knight Netherlands, Larry Leetzow USA, Ian Lewin USA, Peter Bodrogi HU, Bill Simpson CAN, Gunther Heidel Germany, Gunilla Derefeldt Sweden, Edward Yandek USA, Malcolm Nicholson UK, Amy Wang China, Chen Dahua China.

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4. Approval of the Agenda

The Agenda was approved.

5. TC working programme and schedule

Liisa Halonen reminded of the TC terms of reference, these are: ‘ To define mesopic visual performance and related terms. To investigate performance based photometry in the luminance region below approximately 10 cd/m 2 . To propose a model for the basis of performance based mesopic photometry.'

Liisa Halonen reviewed the outcomes of the previous TC1-58 meetings. In the 1 st meeting (Tokyo June 10, 2004) the new terms of reference were agreed. In the 2 nd meeting (León May 17, 2005) the TC working programme (tasks and schedule) was defined. In the 3 rd meeting (Ottawa May 18, 2006) the TC work (outcomes of expert surveys, model comparisons) was introduced and decision was made on generation of further data for model comparisons and analysis. In the 4 th meeting (Beijing July 9, 2007) analysis of MOVE-, X- and Y-models based on three new independent data-sets were presented, the contents of the TC report were agreed and the required future actions needed to accomplish the TC work were discussed.

After the Beijing meeting the first draft of the TC report (Chapters 3 and 4) was sent to members for their comments on October 3, 2007 and comments were asked by October 19, 2007. The second draft of the TC report (Chapters 5 and 6) were sent to members on November 5, 2007. The aim of the 5 th meeting is to agree on the Chapters 3 and 4 of the report, to agree on deadline for further data-sets to be used in model comparison and to agree on the criteria to be used in proposing the mesopic model. After the 5 th meeting the TC report will again be circulated to members for their comments. The aim is to have the 6 th and final meeting of the TC in June 2008 along the Div 1 meeting (possibly in Stockholm Sweden ). The aim of the final meeting is to agree on the TC report to be rendered to Div 1.

The chairman presented the TC working programme which is divided into three main tasks according to the terms of reference. In the working programme generation of new data, analysis of new data and modeling of mesopic data are still in progress. After these are completed the TC can propose a model for the basis of performance based mesopic photometry. The aim is to finalise the TC work within four years from its start, this is by June 2008.

It was agreed that the deadline for receiving any new data sets for model comparisons is January 31, 2008. It was also agreed that the deadline for modeling and model analysis to be carried out within the TC is February 28, 2008.

6. Presentation of recent mesopic research work

Two presentations were given of recent research work done in the mesopic field.

• "Brightness based mesopic photometry" by Ken Sagawa, AIST Japan
  (Attachment 1)
• "Testing visual performance based mesopic models" by Marjukka Eloholma, TKK Lighting Laboratory Finland
  (Attachment 2)

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6. TC report

Marjukka Eloholma presented the draft of the TC report. The general layout (sub-Chapters and their main contents) of Chapters 3 and 4 were agreed. Comments to the Chapters 3 and 4 were jointly collected in the meeting and notes on these were written below each sub-Chapter and presented on the video-screen. The following was discussed and agreed:

• avoid repetition of boundaries for mesopic region (exclude from Ch. 3.1 and remain in Ch. 3.2.1
• mention in Ch. 3.2.1 that there are also other applications besides driving, and that the visual tasks concerned are relevant also there
• In Ch. 3.2.2 inlude links between different parameters of applications (luminance, contrasts, spectra..) and the experimental conditions underlying the X- and MOVE-models
• description of X-model to be checked by the authors of the X-model (within the 2 weeks time for commenting the 3 rd draft of the TC report)
• include short description of road lighting classes (vocabulary definitions)
• the naming of the Y-model and modified MOVE-model is confusing, as both are similar to MOVE-model, but with different upper limits. Use ‘Intermediate models' instead.
• add light source S/P-ratio ranges to the tables presenting the ‘x' and L mes values of the models

Concerning the Chapters 5 and 6 the following was discussed and agreed:

• in Ch. 5.1 include the LRC driver decision data, the CT and RT data from TKK (achromatic targets, presented in Attachment 2) and the new data to be received from UP
• two criteria for testing and comparing the models will be considered and included in the report:
• the spread of mesopic contrasts for equal visual performance in 5.2.1 (as in the 2 nd draft given under 5.1) and
• ‘trend analysis' in 5.2.2 (to evaluate the predictions of the models by presenting visual performance as a function of mesopic luminance)
• the final proposal of a model will be based on these two criteria and the models ability to describe various visual and lighting conditions
• include uncertainty evaluations of the data used for testing and comparison
• the report shall mention restrictions of the data-sets and conditions behind the data-sets used for testing and comparison

Other parts of the report:

• include in Introduction (Chapter 1) safety aspects in night-time driving and the relevance of lighting and viewing conditions for safety
• include in Introduction reference to the brightness-matching models
• in Summary and Conclusions (Chapter 7) include examples of how to use the proposed model: lighting class, light source etc…

It was agreed, that the TC report will be modified accordingly. It was agree that TKK will send the next draft of Chapters 3 and 4 to the members within one week from the meeting, and the members are asked to give their comments within two weeks from that. In case of no comments from a member within the two weeks, it is taken that this member will have no further comments to Chapters 3 and 4.

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7. Future actions

These were discussed and agreed under item 6.

8. Next meeting

The next meeting will be along the Div 1 meeting in June (possibly in Stockholm ).

9. Closure of the meeting

The chairman closed the meeting at 1 p.m. and thanked everyone for a very successful meeting.

• Attachment 1: Presentation by Ken Sagawa
• Attachment 2: Presentation by Marjukka Eloholma