The Journal of the Illuminating Engineering Society of North America    Volume 6     Number 2     October 2009

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GREAT BRITAIN HAS LIGHTED THE WAY

LEARNING FROM THE LAST 100 YEARS OF ILLUMINATION HISTORY

DAVID LOE AND ROSEMARY MCINTOSH

This article considers historical aspects of the Illumination industry in general and the British Illuminating Engineering Society in particular, and from them discusses aspect of lighting’s future. In particular, the past and future of professional lighting institutions, illumination science, lighting design, and lighting energy efficiency are assessed.

REFLECTIONS ON THE LAST ONE HUNDRED YEARS OF LIGHTING IN GREAT BRITAIN

BOOK REVIEW BY DAVID L. DILAURA

A TEST OF THE S/P RATIO AS A CORRELATE FOR BRIGHTNESS PERCEPTION USING RAPID-SEQUENTIAL AND SIDE-BY-SIDE EXPERIMENTAL PROTOCOL

KEVIN W. HOUSER, STEVE A. FOTIOS, AND MICHAEL P. ROYER

An experiment was performed to: 1) Test the hypothesis that the ratio P*(S/P)0.5 can be used to predict the perception of spatial brightness, and 2) directly compare the rapid-sequential and side-by-side evaluation modes for assessing spatial brightness. The two evaluation modes produced comparable results. Though the side-by-side method has in the past been questioned by others, the data herein illustrates that it is neither faulty nor invalid. Red, green, and blue LEDs were employed to create four light settings that were permutations of two S/P ratios (1.7 and 2.6) and two luminance levels (24 and 30 cd/m2). The S/P ratios corresponded to the practical extremities of CCT (2900 and 7200 K) and were structured to have their chromaticity on the blackbody locus. At equal luminance there was no difference in the perception of brightness, irrespective of CCT. At unequal luminance, but when the ratio of P*(S/P)0.5 was set to 1:1, brightness perception was predicted by luminance. These data suggest that spatial brightness perceptions at photopic light levels are unrelated to the S/P ratio of the illumination. These results are consistent with the “prime color” theory of vision that is rooted in the trichromatic nature of human vision.

A METHODOLOGY FOR LOCATING THE MAXIMUM VERTICAL ILLUMINANCE IN STREET LIGHTING

RIAD SARAIJI

Current IESNA recommended practice refers to pedestrian illumination on roadways as a function of the minimum vertical illuminance Ev(min). In this paper, a method is developed to find the location of the maximum Ev(min) along streets. Calculation grids are set on the side walk, along the streets and, along the median. It was found that while the vertical illuminance at one point along the street may be greater than 1 FC, at other points along the longitudinal and lateral axes, the vertical illuminance can be zero even on streets that meet the recommended horizontal illuminance targets.

VERTICAL ILLUMINANCE BASED CROSSWALK ILLUMINATION

RIAD SARAIJI

Current IESNA standards refer to pedestrian lighting in terms of minimum vertical illuminance 1.5 meter above pavement level. Analysis is made to find the vertical illuminance 1.5m above pavement level facing oncoming traffic for typical street lighting configurations. Three types of calculation grids were used to simulate pedestrians on the side walk, on the street and on the median. Streets with and without median are studied with various street lighting layouts such as staggered, and along both sides of the street. It was found that in most cases the vertical illuminance on a two way street peaks on one side of the street while, it is minimal on the other side of the street at the same lateral axis. Plan diagrams of streets showing the locations of vertical illuminance greater than 1 foot-candle and less than 0.2 footcandle are presented.

RESEARCH ON FACIAL RECOGNITION AND COLOR IDENTIFICATION UNDER CMH AND HPS FOR ROAD LIGHTING

QI YAO, YAOJIE SUN, AND YANDAN LIN

Two experiments involving facial recognition and color identification have been done to evaluate the performance of road lighting with HPS and CMH. 48 subjects took part in the facial recognition experiment, and 43 in the color identification experiment, aged 20 to 40. In the facial recognition experiment we used 8 cards with different head portraits for subjects to identify. Three distances were recorded to compare the discriminability: when the subjects could just recognize the gender, guess the identity of the person, and make sure of the identity. In the color identification experiment, participants were asked to identify 8 color cards under HPS and CMH. Results showed that it is easier to recognize faces under CMH. The identification of yellow, green and blue color under CMH is significantly better, while identification of yellow-green under HPS is significantly better.