Figure 2 show the printable color gamut of three commercial printers and Table 1 show the gamut volumes of them. Results represent the gamut achievable with the given printer. Therefore the achievable or reproducible color gamut for Konica Minolta CF3102 is significantly larger than two other printers especially in yellow region for paper A as commercially available paper. In the case of the Konica Minolta Bizhub C450 and Konica Minolta bizhub C451, the Konica Minolta bizhub C451 has larger gamut volume although Konica Minolta bizhub C450 has larger color gamut in blue and magenta area. Figure 2 show printers produce relatively different color gamut shape. As mentioned before comparing the results in terms of gamut volume show, Konica Minolta CF3102 printer has larger gamut volume for the selected paper A. Therefore this printer chooses for investigation the effect of paper characteristics in printable color gamut and reproducibility.
Effect of paper characteristics on color gamut
Figure 3 illustrate reproducible color gamut comparison in CIELAB space for six diffrented papers printed via Konica Minolta CF3102. All papers have relatively same gamut shape but different in gamut volumes. Color gamut volumes of different papers calculated from figure 3 are shown in Table 2. The lowest gamut volume related to paper B and C which specialized from other papers with their lowest paper whiteness. Whiteness is the measured reflectance across all wavelengths in the visible-light spectrum (380-780 nm) and provides information about the color reproduction capability of paper.
The CIE whiteness formula is the most accepted and frequently-used for paper whiteness. Paper whiteness is calculated using equation 1:
W=Y10+800(xn10-x10) +1700(yn10-y10) (1)
where Y10 is the Y-value, x10 and y10 are the chromaticity coordinates of the samples, and xn10 and yn10 are the chromaticity coordinates of the D65 illuminant.
Whiteness measurements for papers are shown in table 3. Papers B and C have lowest whiteness values; while papers A, D and F have higher whiteness values. Figure 4 represents reflectance spectra for all papers. As shown in Figure 4, papers A, D and F tend to have higher reflectance values in the blue region (420-470 nm), resulting in blue white appearance, and most likely due to the presence of optical brighteners. Those papers also have higher negative b* value which confirmed the blue shade of papers (table 4) and lower gamut volume in blue region (figure 3). As mentioned before papers with lower whiteness show lower color gamut volume and also gamut shapes of them show relatively lower lightness value compared to other papers.
Between paper B and C relatively higher roughness of paper C causes to lower gamut volume of it. Roughness is one of the most important factors affecting print quality. A smoother surface can result in a good ink transfer, and vice versa. The...