# Effects of Illuminance Level of Light Source on White Appearance of a Tablet Display
###### Abstract  
The appearance of white significantly impacts display image quality, requiring a neutral white point for optimal performance. This study explores how perceived whiteness changes under ambient illumination levels (150, 300, 600, and 1200 k) and correlated color temperatures (3500 K and 6500 K). As a result, the adapted white points of light sources with different correlated color temperatures are similar at lower ambient illuminance levels. In comparison, their adaptation trends exhibit significant differences at higher illuminance levels. At 150 lx, adapted white points for 3500 K and 6500 K light sources shift toward higher color temperatures and converge. With increased illumination, the 3500 K white point shifts toward its light source, while the 6500 K white point shifts to a higher correlated color temperature. The neural network-based prediction model developed in this study accurately forecasts perceived whiteness across conditions, offering valuable design guidance for the display and lighting industries. white appearance; adapted white; tablet display; illuminance; ambient lightings 2020 IEEEexample: accepted: 10.115.1288.12.  
in which human observers adjusted the color of a self-luminous display stimulus to appear as white as possible under varying adapting luminance and CCT conditions. The results showed that the adjusted chromaticities closely aligned with the adapting chromaticities at higher adapting luminance levels [2]. They reported that adapting luminance and CCT influenced the degree of chromatic adaptation, with adapting luminance having a stronger effect under lower CCT conditions. Since the study found incomplete chromatic adaptation under low CCT adapting conditions, the team subsequently increased the adapting luminance to clarify whether complete color adaptation cannot occur under low adapting color temperatures. The follow-up experiment tested chromatic adaptation under 12 adapting conditions, including four CCT values (2700, 3200, 4000, and 6500 K) and three white luminance levels (1200, 2100, and 3000 cd/m\({}^{2}\)). The results confirmed that, despite significantly increasing luminance, incomplete chromatic adaptation still occurred under 2700 K and 3200 K adapting conditions. However, increasing adapting luminance was found to enhance the degree of adaptation more effectively [3]. [PERSON] et al. conducted a psychophysical experiment to investigate the white appearance of tablet displays under various ambient lighting conditions, including complete darkness, chromaticity on the Planckian locus, and chromaticity deviations from the Planckian locus, to understand human perception of white stimuli and chromatic adaptation [4]. This study found that the chromaticity coordinates of the whiteset stimuli and the boundaries of white appearance varied across lighting conditions. At lower ambient color temperatures, the whiteset chromaticity shifted off the Planckian locus, while at higher temperatures, it aligned with it. Under conditions with the same color temperature but different \(D_{\text{uv}}\) values, the chromaticity of the whiteset stimuli shifted perpendicularly to the Planckian locus. Additionally, the team investigated how the combination of tablet display luminance, text background lightness, and display white points affected visual comfort. They found that the whiteset display color was not rated as the most comfortable for e-reading, whereas the second whiteset color was preferred under 3500 K ambient light [5]. These findings highlight that ambient lighting affects visual comfort and influences white perception. [PERSON] et al. studied how ambient illuminance affects the perceivable white luminance of displays, suggesting that automatic luminance adjustment should depend on each display's maximum white luminance. They recommended a white luminance range of 200-500 cd/m\({}^{2}\) for indoor use to balance visibility and power consumption [6]. [PERSON] et al.