Visual characteristics influencing visual hardness of wood

Abstract

Visual characteristics of wood which influence visual hardness of it were studied. Thirty-four photographs of H-shaped wooden backs of chairs were prepared as specimens. Questionnaires regarding visual hardness and "deluxe" image of specimens were distributed to 32 subjects using the repeated equal-division method. Color values (Y, x and y) of specimens were measured by the colorimeter. Local-area gloss G and spatial ratio of contrasts C were calculated using digital image analyses. G was the index of the local-area glossiness (highlight), and C was the index of the noticeability of wood grain figures. Calculation procedures for both indices were newly developed in this paper. The single correlation coefficient between a visual "hard" image and Y (lightness of specimen) was -0.91, and that between G was 0.83. Using visual "hardness" as a criterion variable and Y and G as predictor variables, a multiple regression analysis was performed. The multiple correlation coefficient was 0.931, the ratio of contribution was 86.7% (significant level 1%). Furthermore C was added to the regression model, above values were 0.942 and 88.8%, respectively (significant level 1%).