Special effect coatings have been increasingly used in many industries (e.g. automotive, plastics industry) over
the past two decades. The measurement of perceived color differences on such coatings cannot be done by means
of traditional color-difference formulas (e.g. CMC(l:c), CIEDE2000, AUDI2000) as they lack to consider distinct
optical properties such as coarseness, glint and goniochromatism. However, there is a need to ensure quality
and colorimetric accuracy when designing and processing special effect coatings. In this paper, we present a
psychophysical experiment intended to serve as a basis for future work on a new generation of color-difference
formula(s) for multiple viewing geometries (viewing and illumination angle). We are especially interested in
assessing whether judging under a single geometry can lead to different results as judging under several (two)
geometries, i.e. whether the sum is more than its part.
Academic results depend strongly on the individual circumstances of students: background, motivation and aptitude. We think that academic activities conducted to increase motivation must be tuned to the special situation of the students. Main goal of this work is analyze the students in the first year of the Degree in Optics and Optometry in the University of Granada and the suitability of an activity designed for those students. Initial data were obtained from a survey inquiring about the reasons to choose this degree, their knowledge of it, and previous academic backgrounds. Results show that: 1) the group is quite heterogeneous, since students have very different background. 2) Reasons to choose the Degree in Optics and Optometry are also very different, and in many cases were selected as a second option. 3) Knowledge and motivations about the Degree are in general quite low. Trying to increase the motivation of the students we designed an academic activity in which we show different topics studied in the Degree. Results show that students that have been involved in this activity are the most motivated and most satisfied with their election of the degree.
The grey scale method is commonly used for investigating differences in material appearance. Specifically, for testing
color difference equations, perceived color differences between sample pairs are obtained by visually comparing to
differences in a series of achromatic sample pairs. Two types of grey scales are known: linear and geometric. Their
instrumental color differences vary linearly or geometrically (i.e., exponentially), respectively. Geometric grey scales are
used in ISO standards and standard procedures of the textile industries.
We compared both types of grey scale in a psychophysical study. Color patches were shown on a color-calibrated
display. Ten observers assessed color differences in sample pairs, with color differences between ΔEab = 0.13 and 2.50.
Assessments were scored by comparison to either a linear or a geometric grey scale, both consisting of six achromatic
pairs. For the linear scale we used color differences ΔEab = 0.0, 0.6, 1.2,..., 3.0. For the geometric scale this was
ΔEab=0.0, 0.4, 0.8, 1.6, 3.2, 6.4. Our results show that for the geometric scale, data from visual scores clutter at the low
end of the scale and do not match the ΔEab range of the grey scale pairs. We explain why this happens, and why this is
mathematically inevitable when studying small color differences with geometric grey scales. Our analysis explains why
previous studies showed larger observer variability for geometric than for linear scales.
Scattered colorimetry, i.e., multi-angle and multi-wavelength absorption spectroscopy performed in the visible spectral range, was used to map three kinds of liquids: extra virgin olive oils, frying oils, and detergents in water. By multivariate processing of the spectral data, the liquids could be classified according to their intrinisic characteristics: geographic area of extra virgin olive oils, degradation of frying oils, and surfactant types and mixtures in water.
Spectral transmittances of three new photochromatic lenses have been measured at different activation states produced by the four luminous sources of a VeriVide CAC 120 cabinet. The greatest transmittance changes were found for the UV and D65 sources. These transmittances changes lead to average CIELAB color differences lower than 6 CIELAB units for the 24 chips of a GretagMacbeth color chart.
We have performed spectroradiometric color measurements at different positions on the floor of two lights booths under two light sources. Uniformity provided by these light booths is enough acceptable for most practical color applications involving relative measurements (e.g. CIELAB coordinates), but not for absolute measurements (e.g. tristimulus values or illuminance). Averge color inconstancy indices are lower than 0.6 CIE94 (1.0 CIELAB) color-difference units.
After each laboratory session, students must answer individually three random multiple choice questions. The corresponding software has been developed by us. This self-evaluation test motivates students before and during sessions performance, and provides objective information to the teacher. The estimated students’ mean satisfaction with this system is 8.1/10.
Random errors were propagated form tristimulus values to CIELAB and CIELUV color coordinates, using the instrumental color measurements of 28 Munsell samples illuminated by 3 light sources and performed by 3 different procedures. The errors found for the CIELAB and CIELUV color coordinates are considerably different for the 3 procedures. These errors are highest for the F source, and similar for TL84 and D65. Under our experimental conditions, we obtain that the instrumental errors for the a and b coordinates are lower than the visual subthresholds predicted by the CIE94 model.