Characterization of Angle Dependent Color Travel of Printed Multi-Color Effect Pigment on Different Color Substrates
Color-travel pigments, which exhibit much more extensive color change as well provide angle-dependent optical effect can be used in many industrial products. In present paper the multi-color effect pigment printed on three different foils with different background color (black, silver and transparent) was investigated. The pigment was based on synthetically produced transparent silicon dioxide platelets coated with titanium dioxide. CIEL*a*b* values and reflection of prints were measured by multi-angle spectrophotometer at constant illumination at an angle of 45o and different viewing angles (-15o, 15°, 25o, 45o, 75o and 110o) were used. The measurements of printed multi-color pigment showed that CIEL*a*b* color coordinates varied to great extents, depending on detection angles as well on color of the printing substrate. The study revealed that pigmnet printed on black background obtained significant change in color. The study has also shown that when viewing angle increases, the reflection curves decreases.
Analysis of the colorimetric properties of goniochromatic colors using the MacAdam limits under different light sources.
Technological innovation in all areas has led to the appearance in recent years of new metallic and pearlescent materials, yet no exhaustive studies have been conducted to assess their colorimetric capabilities. The chromatic variability of these special-effect pigments may largely be due to the three-dimensional effect of their curved shapes and orientations when they are directionally or diffusely illuminated. Our study examines goniochromatic colors using the optimal colors (MacAdam limits) associated with normal colors (photometric scale of relative spectral reflectance from 0 to 1) under certain conventional illuminants and other light sources. From a database of 91 metallic and interference samples and using a multi-gonio-spectrophotometer, we analyzed samples with lightness values of more than 100 and others with lightness values of less than 100, but with higher chromaticities than optimal colors, which places them beyond the MacAdam limits. Our study thus demonstrates the existence of chromatic perceptions beyond the normal solid color associated with these materials and independent of the light source. The challenge for future research, therefore, is to replicate and render these color appearances in current and future color reproduction technologies for computer graphics.
Accurate Color Measurement
In this thesis studies on accurate surface color measurements are considered. Errors in a spectrophotometric measurements are discussed and correction methods introduced. The wavelength interval in a tristimulus integration is considered next. The ASTM weighting functions are tested with a large data set of non fluorescent colors and shown to be useless. The thermochromic effect is also discussed in detail and measured. This thesis shows how thermochromism is based on physical processes. Simple formulas are derived, and shown to explain the experimental data. In conclusion, this thesis shows how commercial instruments should be calibrated for precision color measurements, if one aims at achieving the highest level for measuring accuracy.