With the aim of proposing environmental conditions suitable for persons of all ages to thread a sewing needle, an investigation was conducted on the effects of illumination on the visibility in such conditions.Experiments were carried out using CIE standard illuminant D65 and A as a light source to investigate illuminant color effects on the work. Five colors, green, blue, white, gray and black, were chosen as thread colors and background for sewing, and visibility was assessed for various combinations of these colors. The results showed that the assessment scores for the two light sources were highly correlated, but there was almost no difference in the score among the illuminant colors. Then, effects of illuminance on threading work were assessed at 4 intensities, 50, 200, 500 and 1000 lux. The assessment was made for the sewing thread colors and background, blue, yellow, white and black. Under each condition, the time required to thread a needle was measured, and the sewers were asked about the visibility. Both young and older women answered that the visibility was poor when the color of thread was the same as that of the background. The visibility improved by elevating the light intensity. The correlation was significant at any illuminance. On the other hand, the threading time was shortened by elevating the light intensity. Among the young women, a significant correlation between the visibility and the threading time was found at a low intensity, whereas in the mature women, a significant correlation was observed at all intensities tested. The color difference was highly correlated with delta E*(ab) at all intensities and the effects of differences in lightness on visibility were greatest among those three attributes. From the present results, it was concluded that the illuminance required for threading a sewing needle was 200 lux or more for younger women and 1000 lux or more for older women.
