Colour quality evaluation based on memory colours

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Colour quality evaluation based on memory colours KaHo Sint-Lieven – K.U.Leuven Light & Lighting Laboratory – ESAT/ELECTA Gebroeders Desmetstraat 1, 9000 Gent (Belgium) Tel: +32 92 65 87 13 [email protected] ; [email protected] TC1-69 meeting Princeton, june 17th 2010

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Colour quality evaluation based on memory colours. TC1-69 meeting Princeton, june 17th 2010. KaHo Sint-Lieven – K.U.Leuven Light & Lighting Laboratory – ESAT/ELECTA Gebroeders Desmetstraat 1, 9000 Gent (Belgium) Tel: +32 92 65 87 13 [email protected] ; [email protected]. - PowerPoint PPT Presentation

Transcript of Colour quality evaluation based on memory colours

Page 1: Colour quality evaluation based on memory colours

Colour quality evaluation based on memory colours

KaHo Sint-Lieven – K.U.LeuvenLight & Lighting Laboratory – ESAT/ELECTA

Gebroeders Desmetstraat 1, 9000 Gent (Belgium)Tel: +32 92 65 87 13

[email protected]; [email protected]

TC1-69 meetingPrinceton, june 17th 2010

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Basic Idea:

• The more similar a light source renders the object colours to their memory colours, the better the colour rendering (perceived colour quality).

• (*) Smet K, Ryckaert WR, Pointer MR, Deconinck G, Hanselaer P. Colour Appearance Rating of Familiar Real Objects. Colour Research and Application. Accepted for publication 2010.

Referencing is done to memory colours of familiar objects*,

NOT to a reference illuminant!

Kevin Smet & Peter Hanselaer – A colour rendering metric based on memory colours

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Similarity distributions as special CR indicator functions

• CR&A paper: “Colour appearance rating of familiar real objects”

• Similarity of object chromaticity Xi to memory colour (ai,3,ai,4):

• Si values: hue specific measures for colour rendering/quality

• Summarizing Sa value: Sa = geomean(Si)

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Validation experiments at Light & Lighting Lab• Six 2700K light sources: classic & modern

– Fluo. F4, Fortimo with green filter, Nd Inc., LC (WW/G/R/B led cluster), Halogen, RGB

• 92 observers

• Familiar object set spans entire hue circle

• Scheffé paired comparison experiment

• Five quality descriptors rated on 7 point scale:

– Preference,

– Fidelity

– Vivideness

– Naturalness

– Attractiveness

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Validation experiments at Light & Lighting Lab

• Using the method of Meng, Rosenthal and Rubin3 for comparing correlated correlation coefficients significant differences were found between the MCRI and all other metrics at the p < 0.1 level.

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Kevin Smet & Peter Hanselaer – A colour rendering metric based on memory colours

Spearman ρ preference fidelity vividness naturalness attractivenessCIE CRI 0.49 0.49 0.14 0.60 0.49CQS 0.49 0.49 0.14 0.60 0.49Philips CRI 0.43 0.43 0.09 0.66 0.43MCRI 0.94 0.94 0.77 0.60 0.94

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Validation: Jost-Boissard et al1,2.

-Recap of results presented at CIE conference in Vienna, march 2010

• Using the method of Meng, Rosenthal and Rubin3 for comparing correlated correlation coefficients significant differences were found between the MCRI and all other metrics at the p <0.05 level.

1. Jost-Boissard S, Fontoynont M, Blanc-Gonnet J. Colour Rendering of LED Sources: Visual Experiment on Difference, Fidelity and Preference. CIE Light and Lighting Conference with Special Emphasis on LEDs and Solid State Lighting Budapest; 2009.

2. Jost-Boissard S, Fontoynont M, Blanc-Gonnet J. Thurstone scalings for attractiveness of fruit and vegetables under nine 3000K and eight 4000K light sources. (personal communication). 2009.3. Meng XL, Rosenthal R, Rubin DB. Comparing correlated correlation coefficients. Psychological Bulletin 1992;111:172-175.

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RYG region of hue circle CRI CQS Philips CRI MCRI3000K Pearson ρ 0.18 0.58 0.29 0.96

Spearman ρ 0.03 0.38 0.23 0.88

4000K Pearson ρ 0.30 0.54 0.26 0.97Spearman ρ 0.21 0.29 0.17 0.90

Special indices used in recalculation: MCRI (all but smurf & lavender were omitted); CIE CRI (1-4, 9-11 & 13-14); CQS (7-15); Philips CRI (-20°-150°).

Kevin Smet & Peter Hanselaer – A colour rendering metric based on memory colours

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Validation: Jost-Boissard et al.

3000K light sources:

4000K light sources:

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Conclusion

An evaluation of the quality of lighting using a metric based on memory colours correlated well with the visual results for preference, fidelity and attractiveness. It was also found to be significantly (p < 0.1) better at predicting the visual ranking of light sources for those quality descriptors.

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