Affective judgment of viewing an illuminated in-product space in relation to the surrounding lighting

This study deals with the appropriate lighting conditions within in-product spaces, focusing on two parameters: illuminance and correlated color temperature (CCT), in relation to the surrounding light conditions. The study was structured around two main experiments. The first experiment investigated how the perceived illuminance inside these in-product spaces correlates with the intensity of surrounding light, demonstrating that preferred interior lighting levels are directly influenced by surrounding lighting conditions and the color of the interior surfaces. The optimal illuminance was predicted using a regression model: Best Illuminance = 18.20 × L value of product +.70 × Surrounding illuminance - 514.30 ( R 2 = .75), indicating that preferred in-product illuminance increases with higher surrounding illuminance. The second experiment examined the perception of ’whiteness’ and preference for in-product space lighting CCT under varying CCT of surrounding light. The results showed that higher surrounding CCT significantly increased the perceived white point of in-product. The perceived white point was predicted using a model: 10 6 ∕Correlated Color Temperature of Whitest Light = 3.13 × 10 5 × Surrounding Correlated Color Temperature +150.69 ( R 2 = .57), indicating that the perceived white point shifts toward higher CCT under cooler surroundings. Additionally, participants preferred a higher CCT than the perceptual white point as the lighting within the in-product space. These experiments provide concrete guidelines for designing lighting within in-product spaces, offering predictive models for both illuminance and CCT to support more effective and user-preferred lighting solutions across various product settings. • Study explores optimal lighting conditions of in-product spaces under surrounding illuminance. • Preferred in-product illuminance increases with higher surrounding illuminance. • Both perceived and preferred in-product CCT align with surrounding CCT. • The preferred CCT for in-product space lighting was higher than the perceived white point.