1. Cheng Li Supervisor : Prof. M. Ronnier Luo Colour and Imaging Group Department of Colour Science Evaluation of Visual Colour Fidelity

2. Aim A reliable experimental method for evaluating the colour rendering property between test and reference illuminants Focus on ‘colour fidelity’

3. Light Sources L (cd/m²) xyCCT (K)CRI( DE ) Reference lamp44.70.30890.32470.0002675796B(0.50) Simulator 142.70.30750.32060.0016688399A(0.21) Simulator 245.70.30640.31960.0015696581D(1.07) Simulator 344.10.30880.32070.0023680380E (3.16) Simulator 446.50.31080.31950.0040670252E (4.82) mean44.70.30850.32100.0019682282 standard deviation1.50.00170.00210.001414019

4. 15 Test Samples

5. Viewing Cabinets 9 observers and each repeated twice

6. Experimental Procedure Task: To scale the visual colour difference of test samples viewed under one of the test simulators and then under the reference lamp Steps: 1.Observers were first asked to adapt to the test source for 15 seconds and remember the colour of a randomly selected sample; 2.Observers were adapted under the reference lamp for another 15 seconds; 3.After re-adaptation under the reference source, the test sample was shown again, and the observers were asked to estimate the colour difference between the colour seen under the reference lamp and that memorised colour by using the grey scale method Note:If observers could not memorise the colour previously seen under the test simulator, they were allowed to see the test sample again, but 15 seconds adaptation time under both test source and reference lamp had to be applied.

7. Results CVs for Observer RepeatabilityCVs for Observer Accuracy Test Simulator Observers12341234 1111213248262524 21324223210151820 31820284119161723 420 183015 22 5182217912221627 62425314214192447 7192927291221 26 8614713 1413 91635143812181326 Ave. 162220291318 25 Max. 2435314219262547

8. Effect of colour difference equations Colour difference formulae Chromatic adaptation transformation Test simulators 1234mean CIE 1964 U*V*W* von Kries4851534148 CAT025051524148 CIELAB von Kries3430392331 CAT023130392331 CIEDE2000 von Kries3931362332 CAT023830362232 CIECAM023430432533 CAM02-UCS3623422231 CV values for different colour difference calculation methods for each simulator

9. Results Colour Difference Formulae Chromatic adaptation transformations CVs CIEU*V*W* von Kries57 CAT0257 CIELAB von Kries43 CAT0242 CIEDE2000 von Kries44 CAT0243 CIECAM0245 CAM02-UCS41 CV values for different colour difference calculation methods for all simulators

10. Results: r=0.8641 r=0.9203 Less scatter for CAM02-UCS than current CRI

11. CRI-CAM02UCS Colour differences of 14 reflective samples are calculated in the CAM02-UCS uniform colour space CRI-CAM02UCS The CRI-CAM02UCS is re-scaled to keep consistence with the original CIE CRI

12. CRI-CAM02UCS CIE CRICRI-CAM02UCS Reference lamp96 Simulator 199 Simulator 28183 Simulator 38084 Simulator 45261

13. Colour and Imaging Group Department of Colour Science Thank you