Modern industrial color measuring instruments are grouped into three levels according to their performance (in terms of accuracy, reproducibility and repeatability) and technical specifications: top-of-the-line, mid-range and entry-level. Due to advances in the design, manufacturing and control of the instruments, top-of-the-line specificatins are no longer achievable only for bench-top instruments: portable and on-line spectrophotometers are also available at this level. Recent advances made special features such as spectrogoniometry and double-monochromator, spectrofluorimetry - formerly encountered only in research laboratories - available in industrial instruments. Entry-level instruments have become more rugged and affordable than ever. The authors tested over 30 color measuring spectrophotometers in laboratory and industry, and found that the performance of well-maintained and well-operated instruments is within the original specficiations provided by the manufacturers.
253 visual observers, at the average level of between 'unselected' (inexperienced) and 'in-plant applicants' have been tested under controlled industrial conditions using the Ishihara or T.M.C. (Murakami) pseudoisochromatic plates, the Farnworth-Munsell 100 Hue Test (FM), the HVC Color Vision Skill Test (HVC) and the Japanese Color Aptitude Test (JCAT). There is only loose correlation between the FM and the HVC tests. The FM scores do not improve significantly by retesting, while the HVC scores can be improved through training, e.g. by using the JCAT. We found practically no correlation between the performance in visual pass/fail decisions and the FM or the HVC scores. Three different editions (3 copies from 1991, 3 from 1997 and two from 1998) of the HVC test were measured and analyzed. They showed good, in the latest edition very good, intra-edition repeatability and good inter-edition reproducibility.
The approach and findings during the application of instrumental color quality control in industry are described, where the best tolerance formulae and tolerance limits were determined by correlating visual and instrumental evaluations. A panel of previously tested observers evaluated a collection of samples taken from production and color measurements are then compared to these assessments, according to different color difference formulae. T he formula and the limit giving the best agreement with visual evaluations were determined with two different methods. For a large variety of textile substrates, processes and market situations the CMC(2:1) formula was always the best or one of the bests, but the limits varied widely, according to the individual application. Additional shade sorting, based on the tolerance limit, was also applied in several companies. The ideal box size was also determined by comparing visual and instrumental evaluations. The application as logistical tools was established according to individual necessities.
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