Large Hemispherical SurfaceA large (diameter 1.98 m) uniformly illuminated hemispherical surface is used for various visibility experiments. The interior is painted white and illuminated with daylight fluorescent lamps (correlated colour temperature 5400 K). The hemisphere surface luminance can be adjusted in the mesopic to photopic luminance regions. Different coloured LEDs are used as visual targets. The intensity of the targets is adjustable. Visual targets can be located in foveal (on-axis) vision and at various eccentricities (10°, 20°, 30°, 45° and 60°) on the horizontal line aside the on-axis location. The large hemispherical surface can be used for e.g. contrast threshold and reaction time experiments in varied lighting and viewing conditions. Reaction times are recorded with a System flash meter.