The effect of veiling luminance on the disability glare of car headlamps designed in Iran

Objectives. One of the main risk factors involved in increasing driving accidents at night is due to the veiling luminance of the car's headlights reducing the contrast of images in the retina and, thus, reducing the visual performance of drivers. The aim of this study is to investigate the veiling luminance caused by the headlights of the best-selling vehicles in Iran. Methods. Using the Stiles-Holiday disability glare equation, the veiling luminance of headlights of common vehicles at distances of 10-100 m for both high-beam and low-beam modes of oncoming vehicles was measured on a road for healthy (young, middle-aged and older) drivers. Results. Under high-beam illumination, as the cars approached each other, the average illuminance of the car headlights gradually increased. Moreover, age had a significant impact on the veiling luminance. This study also showed that, in same-age groups, the Samand Souren and Peugeot Pars cars had the highest and lowest mean veiling luminance, respectively. Conclusion. The findings showed that the illuminance (at large distances between two cars) and the angle between the source of glare and the eyes of drivers (as two cars approach to each other) have a dominant influence on the disability glare.

Perception of a Black Room Seen Through a Veiling Luminance

When a black room (a room painted black and filled with objects painted black) is viewed through a veiling luminance, how does it appear? Prior work on black rooms and white rooms suggests the room will appear white because mutual illumination in the high-reflectance white room lowers image contrast, and the veil also lowers image contrast. Other work reporting high lightness constancy for three-dimensional scenes viewed through a veil suggests the veil will not make the room appear lighter. Because mutual illumination also modifies the pattern of luminance gradients across the room while the veil does not, we were able to tease apart local luminance gradients from overall luminance contrast by presenting observers with a black room viewed through a veiling luminance. The room appeared white, and no veil was perceived. This suggests that lightness judgments in a room of one reflectance depend on overall luminance contrast only.