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Table 1 Comparison of chromatic coordinates measured experimentally and calculated from image analysis for clean and tarnished copper and silver coupons from Fig. 5.

From: Design and validation of tailored colour reference charts for monitoring cultural heritage degradation

  Clean Tarnished
Measured Calculated (raw) Linear calibration Spatial calibration Measured Calculated (raw) Linear calibration Spatial calibration
Copper
 L* (10°/D65) 79.66 73.44 74.01 76.71 64.92 70.22 63.36 64.91
 a* (10°/D65) 14.30 12.83 19.87 14.09 24.83 25.10 28.00 25.68
 b* (10°/D65) 15.10 17.47 13.69 15.34 42.03 48.74 36.50 45.40
Silver
 L* (10°/D65) 91.87 79.60 80.87 81.06 72.44 74.92 66.87 68.45
 a* (10°/D65) 0.10 0.20 2.35 −2.11 5.00 4.34 0.65 4.64
 b* (10°/D65) 3.63 1.82 −0.63 0.91 26.82 31.19 26.81 26.55
  1. Raw, linear calibrated and spatial calibration calculated values are presented