![]() ![]() The visual comparison of color cards with printing inks, coloring or colored coatings is, however, faulty, since it is often impossible to check it objectively under the same conditions. Based on these catalogs, visual inspections can be carried out during the production process and quality control. Many comparative measurements take the color values from standard color systems or color catalogs into account. Ideally, both parties use identical measuring devices from one manufacturer. It is particularly important to achieve an agreement about measurement parameters (color space, measurement geometry, measuring aperture, light type, SCI, SCE, Spin, Spex) otherwise the comparability of the measurement values is not possible. Does it go about company's internal measurements, during which the process reliability and quality are to be checked based on specially defined color values? Or should the external requirements of customers or suppliers be taken into account? If external requirements are decisive, a preliminary clarification between the parties, concerning which measuring instruments are to be used, is required. Internal inspection or external requirements?Īn important point, which must be clarified before the purchase of a color measuring device, refers to the present reference values. Particularly in case of spectrometers, a spectral resolution of the measuring devices must also be taken into account. When selecting the accuracy requirements, attention should be paid to the reproducibility of the measurement results as well as the comparability of different measuring instruments of one series. Therefore, it makes sense to use the 45 / 0 geometry, when the visual impression an object has on humans should be adjusted. In contrast, the 45 / 0 measurement geometry produces a directed reflection which corresponds more to human perception. Partially, measuring instruments with this geometry also have optical shines (SCI) (SCI) in order to allow the gloss effect influence the measurement or not. With this geometry, one can, so to say, look inside the color. The d / 8 measurement geometry produces diffuse light, thereby the effect of the surface texture in terms of gloss and roughness is reduced. Since the measurement geometry cannot be changed or adjusted afterwards, clarity should be provided before the purchase. The choice of the correct or incorrect measurement geometry can have a considerable effect on the measurement results and lead to interpretational errors during the information exchange between customers and / or suppliers. The measurement geometry describes the alignment between the emitting light source of the measuring device and the surface of the object to be measured as well as the alignment of the sensor to the reflecting surface of the object to be measured. For the use in the production process, the goods receipt and output control, as well as in quality control, the color comparison measurements with the simple representation of color differences and deltaE values by means of color meters are generally sufficient. The reason for this is that usually different spectral reflection properties of the surfaces are caused by the use of different pigments.įor this reason, spectrometers are preferably used in research and development as well as in cases when colors and color spectra have to be determined very precisely. In case of this phenomenon, for example, two different objects under a certain light source appear to be of the same color, but under a different light source a distinct color difference is visible and evident. Thus, not only color coordinates can be determined, but also the spectral distribution and intensity can be determined and represented much more precisely. Depending on the quality of the device, spectrometers are equipped with significantly more sensors so that the devices have a wavelength-specific sensitivity in a single-digit nanometer range. Though spectrometer works according to the identical basic principle, the significant difference to color meter is sensitivity and the number of sensors. The color values determined in this way are represented as X, Y and Z values on the display by the measuring devices, the conversion into common color spaces such as CIELab or RGB is carried out by most devices automatically. In the human eye the three basic colors red, green and blue are recorded over three different cone types, color meter imitates this color perception by means of 3 color sensors with almost identical spectral sensitivity in the areas of red, green and blue. Color meter works according to the tristimulus absorption and imitates human vision. ![]()
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