PubMed · 10123936
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D K Gardner. 1990. Diagnostic imaging centers.. https://pubmed.ncbi.nlm.nih.gov/10123936/
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Borders defined by small changes in brightness (luminance contrast) or by differences in colour (chromatic contrast) appear to move more slowly than those defined by strong luminance contrast. As spatial coding is influenced by motion, if placed in close proximity, the different types of moving border might appear to drift apart. Using this configuration, we show here that observers instead report a clear illusory spatial jitter of the low-luminance-contrast boundary. This visible interaction between motion and spatial-position coding occurred at a characteristic rate (approximately 22.3 Hz), although the stimulus motion was continuous and invariant. The jitter rate did not vary with the speed of movement. The jitter was not due to small involuntary movements of the eyes, because it only occurred at a specific point within the stimulus, the low-luminance-contrast boundary. These findings show that the human visual system contains a neural mechanism that periodically resolves the spatial conflict created by adjacent moving borders that have the same physical but different perceptual speeds.
The objective of this study was to evaluate the influence of the illuminating/viewing aperture diameter of 11 mm/8 mm and 3 mm/3 mm and measuring geometry on the color and polymerization color changes of dental resin composites. Color of resin composites of 12 mm in diameter was measured on a reflection spectrophotometer with SCE and SCI geometry under D65 illumination. Before polymerization, difference in the three-color coordinates by the material was prominent in spite of the fact that the shade designation of all materials was the same. After polymerization, L* value decreased in hybrid composites but not in packable composites, and changes in a* value were small. When the same aperture size was used, polymerization color change with the SCE was generally higher than those with the SCI. Measured color was different by the aperture size, and the color difference was 16.82-27.05 before polymerization and 20.09-28.51 after polymerization. General trends of polymerization color change were similar in both aperture sizes. Polymerization color changes with 3-mm aperture size were higher than those with 8-mm aperture size in hybrid resin composites in both geometries (p < 0.05); however, the color change was material dependent in the case of packable resin composites.