An Objective-Subjective Analytical Approach to Evaluate Lighting Quality A Critical Analysis of the King s College Antechapel, Cambridge

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1 An Objective-Subjective Analytical Approach to Evaluate Lighting Quality A Critical Analysis of the King s College Antechapel, Cambridge Villian W.L. Lo Supervisor: Professor Koen Steemers InSitu Graduate Colloquium 2013

2 OUTLINE Project background Research objectives Methodologies Current stage of research

3 PROJECT BACKGROUND October King s College Antechapel Lighting Project To offer advice on lighting appraisal and lighting quality created by a new optic system as a replacement for the existing light setting Existing: low luminous intensity, uneven luminous distribution and visual distraction

4 KING S COLLEGE ANTECHAPEL LIGHTING PROJECT Comparative Analysis of four artificial lighting scenarios 1) All Lighting 2) Rig Lighting 3) Interim Lighting 4) Proposed Lighting

5 RESEARCH OBJECTIVES To develop a theoretical model that correlates objective measures with subjective attributes in lighting research Developed originally by acoustic researchers between 1960s and 1980s A mathematical procedure that evaluates subjective responses with objective parameters To develop a technique through experimenting with methods: To analyse the nature of problems in lighting research To define lighting parameters

6 RESEARCH METHODOLOGIES Lighting modelling and HDR imaging as analytical tools Mathematical definitions Field experiments and screen experiments Subjective descriptors

7 Distance from North Elevation (m) LIGHTING MODELLING Work-in-Progress Radiance model: Luminance/Illuminance data extraction 13.6 Illuminance Distribution (Lux) at Workplane Level of 1200mm Interim Lighting Distance from Screen (m) Lux

8 Current Lighting Research LIGHTING MODELLING Visual Analysis: Light Patterns

9 LIGHTING MODELLING Visual Analysis: Shadow Radiance Simulation: Shadow study

10 LUMINANCE FIELD OF THE ANTECHAPEL: Sampling working illumination and visual field of the occupants

11 Musicians Conductor Audience members

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15 HIGH DYNAMIC RANGE (HDR) IMAGING 43 RAW images captured with shutter speed varies from 1/1000s to 15s, i.e. a dynamic range of 14000:1 Superimpose histological details of retina on an HDR image Correlate facts about visual acuity with visual field mathematically Binocular Field Monocular Crescent Revised perimeter chart: Indicates corresponding position of the fovea, parafovea and perifovea Visual degree from foveala and visual angle subtended at the eye are plotted on the macular region

16 HIGH DYNAMIC RANGE (HDR) IMAGING Translate luminance data into false colour images For example, at Spot DEF: Rig Lighting Interim Lighting All Lighting

17 Luminance (cdm -2 ) HIGH DYNAMIC RANGE (HDR) IMAGING Translate luminance and pixel data into graphs For example, at Spot DEF:

18 OBJECTIVE ATTRIBUTES: MATHEMATICAL FUNCTIONS Possible Objective Attribute Relative Visual Acuity Uniformity Ratio (I) Mathematical Function derived from HDR images Sum of Relative Luminance (RLV sum ) = (LV avg x /y ) Relative Visual angle subtended at the eye Ratio of the average luminance seen within the left and right monocular crescent: (LLM avg + LRM avg )/2 :Lb avg Uniformity Ratio (II) Ratio of the average luminance seen within the left monocular crescent to that within the right monocular crescent: LLM avg : LRM avg Uniformity Ratio (III): variation Variance/ Standard Deviation of Luminance between between x and y from the foveala: Pixel Intensity Brightness = Average pixel intensity (IM) Contrast = Standard Deviation of pixel intensity (ISD) Overall Impression Semantic Differential Scale 1 to 7

19 POSSIBLE SUBJECTIVE ATTRIBUTES Possible Subjective Attributes Visual Clarity Uniformity Brightness Intimacy Task performance Comfort Overall Assessment of the Antechapel s Lighting Quality

20 FIRST TRIAL RUN 22 nd April 8.30pm with 6 subjects

21 30 x dummies (musicians) 10 x dummies (audience members)

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23 THE END Villian W.L. Lo InSitu Graduate Colloquium 2013