Zenith luminance and sky luminance distributions for daylighting calculations

Detection of changes in luminance distributions.

How well can observers detect the presence of a change in luminance distributions? Performance was measured in three experiments. Observers viewed pairs of grayscale images on a calibrated CRT display. Each image was a checkerboard. All luminances in one image of each pair consisted of random draws from a single probability distribution. For the other image, some patch luminances consisted of r...

Color and luminance asymmetries in the clear sky.

A long-standing assumption about the clear sky is that its colors and luminances are distributed symmetrically about the principal plane. As useful as this approximation is, our digital-image analyses show that clear-sky color and luminance routinely depart perceptibly from exact symmetry. These analyses reconfirm our earlier measurements with narrow field-of-view spectroradiometers [J. Opt. So...

Luminance Metrics for Roadway Lighting

Automatic spatial association for luminance.

In the present study, we investigated whether luminance and the side of response execution are associated, showing a SNARC-like effect (faster responses with the left hand for dark stimuli, and vice versa for light stimuli). A total of 30 participants were tested in two experiments. In Experiment 1, the association between space and the luminance of chromatic stimuli was directly tested (bright...

Luminance Requirements for Lighted Signage

Light-emitting diode (LED) technology is presently targeted to displace traditional light sources in backlighted signage. The literature shows that brightness and contrast are perhaps the two most important elements of a sign that determine its attention-getting capabilities and its legibility. Presently, there are no luminance standards for signage, and the practice of developing brighter sign...