The relationship between the surface profile and the image clearness of paint coatings was studied. The relation between the image clearness and the standard deviation σ of the local slopes on the painted surface could be represented in a simple equation, based on the assumption that the distribution function of the local slopes was the normal distribution. σ values were calculated by the equation with the image clearness values which measured by two different types of apparatus, and compared with σ which was directly measured by schlieren method. The good agreement between these σ values was observed, which proved the propriety of the equation.
In addition, the conversion formulas for image clearness values measured in different systems were obtained, and their propriety was also demonstrated.
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