The shape of image luminance histograms is related to material perception. We investigated how the luminance histogram contributed to improvements in the perceived quality of wood images by examining various natural wood and adhesive vinyl sheets with printed wood grain. In the first experiment, we visually evaluated the perceived quality of wood samples. In addition, we measured the colorimetric parameters of the wood samples and calculated statistics of image luminance. The relationship between visual evaluation scores and image statistics suggested that skewness and kurtosis affected the perceived quality of wood. In the second experiment, we evaluated the perceived quality of wood images with altered luminance skewness and kurtosis using a paired comparison method. Our result suggests that wood images are more realistic if the skewness of the luminance histogram is slightly negative.

:Recently, the demand for printed wood grain has been growing. The elements of wood grain of natural wood and printed wood grain are different. These differences result in the differences in characteristics of their corresponding spatial frequencies, and would influence the identification of natural and printed wood grain. In our study, we analyzed the spatial frequency of wood samples. Results showed that a more noticeable the difference in the samples was seen in the high spatial frequency region. We also visually evaluated the discriminability between natural and printed wood grain for various viewing distances. The results demonstrated that it was difficult to distinguish between natural and printed wood grain at long distances, whereas, it was easy at short distances. This suggests that the differences in the high spatial frequency and the presence or absence of half tone has an effect on the distinguishability in natural and printed wood grain samples.