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Table 6 Test results of the model-based and projection-based algorithms when applying the sensor responses generated by 80-nm FWHM evenly spread sensors

From: Analysis of colour constancy algorithms using the knowledge of variation of correlated colour temperature of daylight with solar elevation

 

Phase of day

Solar elevation

Projection-based algorithm

Model-based algorithm

Without solar elevation and phase of day

With solar elevation and phase of day

Improvement (%)

Without solar elevation and phase of day

With solar elevation and phase of day

Improvement (%)

Quarter 1

Morning

−10 to 20

13.5

10.8

−20.0

12.5

8.2

−34.4

Midday

20 to 90

11.6

26.4

+128

9.3

25.8

+177

Evening

−10 to 20

9.0

8.2

−8.9

8.2

7.3

−10.9

Quarter 2

Morning

−10 to 20

13.8

13.3

−3.6

12.7

12.9

+1.6

Midday

20 to 90

9.0

26.5

+194

7.5

26.6

+255

Evening

−10 to 20

7.6

13.4

+76.3

6.1

13.0

+113

Quarter 3

Morning

−10 to 20

8.1

8.3

+2.5

7.2

7.5

+4.2

Midday

20 to 90

8.9

26.1

+193

7.2

26.1

+263

Evening

−10 to 20

9.8

13.3

+35.7

7.6

11.5

+51.3

Quarter 4

Morning

−10 to 20

10.4

10.8

+3.8

9.1

9.8

+7.7

Midday

20 to 90

7.2

23.4

+225

5.8

23.2

+300

Evening

−10 to 20

7.1

9.0

+26.8

5.6

7.9

+41.0

  1. In this test, Munsell samples separated by 1-CIELab units and measured daylight spectra were applied. Each sensor response was multiplied by normally distributed hundred random numbers with a mean value of 1 and standard deviation 1% and the resulting linear responses were quantised to 10 bits. The Mahalanobis distance boundary settings were applied in three phases of the day (morning, midday and evening) with elevation threshold of 20°.