Brightness function across varying adapting luminance in head-mounted displays.

Brightness functions describe the relationship between perceived brightness and stimulus luminance under various viewing conditions. Previous studies have highlighted the effects of adapting luminance and ambient conditions on perceived brightness. Brightness functions are essential for ensuring accurate tone reproduction across different media and viewing conditions. Most prior research on this topic has been conducted in real environments using either simple or complex stimuli. With the development of head-mounted displays (HMDs), the need for accurate tone reproduction in 3D virtual scenes has emerged, requiring accurate brightness functions for different adapting luminance levels. However, brightness perception in HMDs has been scarcely investigated, and it remains unclear whether traditional brightness functions are applicable to HMDs. To address this gap, this study employed a magnitude estimation method to collect brightness ratings for stimuli in complex images under varying adapting luminance levels. The results revealed a systematic deviation between the observed brightness ratings and the model predictions, with stimuli appearing brighter in HMDs, particularly under low adapting luminance levels. This finding suggests that viewing conditions in HMDs-likely influenced by their limited field of view-affect brightness perception compared to real-world scenes.