For both uniform and non-uniform lighting, we investigated user's preferences for wall surface illuminance compared with table surface illuminance, in order to obtain guidelines for comfortable use.
In an interior space, the wall surface in the user's visual direction is an important surface that sometimes stops visual direction. In this case, the user tends to excessively observe the floor surfacebetween the walls in front of the user.
For example, wall surface illuminance is influenced not only by table surface illuminance, but also by the brightness around the table.
Then, for both uniform and non-uniform lighting, the desirable wall surface illuminance to the table surface illuminance was clarified in this research.
It became clear that the relationship between the table surface illuminance and the wall surface illuminance is exponential, so it shows little difference between uniform and non-uniform lighting. And, it can be understood that the exponent of a non-uniform lighting is smaller than uniform lighting.
In a non-uniform lighting, the maximum or optimum value of the exponent is in the range from 0 to 0.1 and it can be seen that this value tends to produce stable illuminance, independent of the table surface illuminance.
Otherwise, in a non-uniform lighting, the preferable wall surface illuminance isslightly, influenced by table surface illuminance. For non-uniform lighting in which the area around the table is dark, it can be considered that the wall surface illuminance is influenced more by the darkness of the table area than by the brightness of the table surface.
Furthermore, as a reference for lighting design, recommended values of preferable wall surface illuminance are shown in the full paper for 400, 700, and 1000 lx of table surface illuminance.
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