Display Brightness Change Over Time after Ambient Luminance Change

Abstract

The adaptation of eyes to ambient lighting changes with the time exposed to the environment. It takes about two minutes for more than 90% of adaptation. The degree of adaptation impacts display appearance. There has been a lot of research on the way in which display appearance changes depending on the illuminance or chromaticity of the ambient lighting. Most studies have focused on display appearance perceived by a human in a sufficiently adapted state to the environment. The degree of adaptation would be changed over time of exposure to the light, thereby changing the display appearance. This study investigates the degree to which display brightness changes according to changes in illuminance of the ambient lighting. The basic research was conducted from the point of view of brightness, which is the most basic element of the color appearance. The change to brightness over time was tracked by evaluating the stimuli at regular intervals of time In the experiment, the ambient lightings were set according to the luminance ratio between the display and the ambient lighting. There were two ambient lightings were brighter than the display and one lighting in which the display is brighter than the ambient lighting. Three types of lighting different illuminants with 6500K of CCT were used in this experiment. An experiment was conducted in which the lighting was changed between a darker and brighter ambient lighting than the display. It was divided into two sessions according to the illuminance of the dark lighting. There were 4 lighting settings in each session: static dark lighting, Static bright lighting, dynamic becoming darker lighting, dynamic becoming brighter lighting. static and dynamic indicate whether there is a change in lighting. For each setting, there were two types of brightness state: static state and dynamic state. If there was an adaptation time for ambient lighting before the evaluation, it was specified as a static state. On the other hand, if the evaluation was conducted immediately after the lighting conversion, the evaluation was classified as a dynamic state. For the stimuli, seven levels of luminance were used in the experiment. The stimulus with medium luminance was designated as a reference stimulus. The participants numerically responded to the brightness of the stimuli presented by random order once every 5 seconds through the magnitude estimations. The experimental results were compared with the average of the participant's responses. The brightness evaluated for each ambient lighting had different results depending on the static or dynamic state. Besides, the change of the estimated brightness in a dynamic state was analyzed through the responses with a regular interval of time. The "Pop-up effect”, in which the display is perceived brighter immediately after the lighting conversion, was observed. The estimated time for adaptation was then found. According to the estimated time and intensity of the “Pop-up effect,” the parameters of the lighting and the display that affect the degree of the Pop-up effect were proposed. The adaptation is affected by the difference in illuminance between the lightings, the direction of lighting change, and the luminance of the display.