Optical Society of San Diego

OSSD First Place Award

Senior Division
(High Schools; 9th - 12th Grades)

"Quantifying the Effect of Tungsten Illumination on Color Rendering of Low-Pressure Sodium Lights"

(Photo: Julie Rucker)

Jessica Rucker
10th Grade
Torrey Pines High School

Senior Sweepstakes Winner
Greater San Diego Science and Engineering Fair

Greater San Diego Science and Engineering Fair
Special Award: Taiwanese American Foundation - Trip to Taiwan

Greater San Diego Science and Engineering Fair
Professional Society Awards:

General Atomics Fusion Program
Mt. Laguna Observatory Association
Optical Society of San Diego
San Diego County Optometric Society
Society of Women Engineers
U.S. Air Force
Villanova University

3rd Place Award in Physics and Astronomy
California State Science Fair 2004
in Los Angeles, CA

Certificate of Award: International Society for Optical Engineering (SPIE)

California State Science Fair 2004
Category Winners in Physics & Astronomy
Senior Division

From left to right are: Andre Maranhao (Honorable Mention), Jessica J. Rucker (Third Place),
Anthony T. Nguyen (Second Place), and Peiran Gao (First Place).
(Photo from CSSF Web Site)

Advisor: Victoria Coordt
2004 Greater San Diego Science and Engineering Fair
Science Teacher of the Year Award: Senior Division

The following was taken from the San Diego Union-Tribune,

Science fair winners investigate variety of topics

By Bruce Lieberman
STAFF WRITER
March 27, 2004

Astronomers have long complained that outdoor lights obscure the night sky, limiting research, but police and other public safety workers say they need them bright enough to illuminate colors. Jessica Rucker, a junior at Torrey Pines High School in Encinitas, thinks she may have one answer.

In a project for the 50th annual Greater San Diego Science and Engineering Fair, Rucker, 16, took low-pressure sodium lamps – the kind astronomers want cities to use – and augmented them with tungsten lamps to see which power combination might illuminate colors but keep lighting low as possible.

The result? Low-pressure sodium lights augmented by about 25 percent tungsten lights rendered colors nearly normal. "Anything with a broader spectrum, with more light colors represented, is a problem for astronomers," Jessica, a poised and articulate teenager, said yesterday.

Rucker's project, one of four top winners in the fair's senior division, highlighted the impressive talent displayed at the Balboa Park Activity Center. Nearly 730 students from San Diego and Imperial counties entered projects in this year's fair.

Effect of Tungsten Illumination on Color Rendering of Low-Pressure Sodium

Jessica Rucker
2004 California State Science Fair

Introduction: Light pollution from urban centers is a major threat to astronomical observations around the world and especially to San Diego, home to both the Palomar and Mt. Laguna Observatories. To help preserve the night sky, low-pressure sodium (LPS) lighting is recommended for applications near observatories, but widespread use of this efficient lighting is hindered because cities object to the poor color rendering provided by LPS for reasons of safety and aesthetics. Can a compromise be achieved by combining LPS with small amounts of other types of lighting in order to improve color rendering while benefiting from the efficiency and environmental aspects of LPS?

Abstract

Objective: Low-pressure sodium vapor (LPS) is efficient and astronomer-friendly lighting, but its narrow band of emissions results in poor color rendering of illuminated objects. This experiment determines whether a model can be developed to predict the amount of broader-spectrum incandescent illumination required to supplement LPS in order to render near normal color perception.

Methods/Materials: Using a digital camera, I took over 1600 images of six Newtonian color targets illuminated by 4300 lux from an 18-watt LPS lamp and variable lux from a 100-watt tungsten lamp, ranging from 0 to 3080 lux regulated by a dimmer and measured photometrically. I developed a C++ computer program to convert RGB pixel data of each CCD image into CIE L*a*b values and to calculate delta E color differences against a 100% tungsten color reference. I established a "Color Rendering Value (CRV)" from 0-100 for each sample, based on a weighted average of the delta Es of the Newtonian spectrum. CRVs of samples were averaged and graphed to determine a best-fit mathematical correlation to CRV as a function of tungsten percentage.

Results: The CRV for illumination with 2.5% tungsten was 2.3, 3.4 with 15.0%, 13.7 with 26.0%, 30.1 with 35.9%, and 41.2 with 42.7% tungsten illumination. A model correlating tungsten percentage, "W", to color perception as indexed by CRV was derived: CRV = 38 arctan(.07 W - 3.2) + 49.5, with acceptable color rendition at CRV > 13.

Conclusions: The results of this experiment indicate that LPS lighting augmented by approximately 26% tungsten illumination may render near normal color perception, with higher standards achievable with higher amounts of tungsten illumination. Applications of LPS combined with broader-spectrum illumination may present an alternative for outdoor lighting that is both color-acceptable as well as cost-efficient and environmentally responsible.

Thank You Melles Griot

The OSSD would like to recognize and thank Melles Griot for their past and ongoing support of our Educational Outreach efforts. They have provide HeNe Lasers for both the Senior and Junior division OSSD First Place Winners at the Greater San Diego Science and Engineering Fair for over five years and continue to assist the OSSD with encouraging optic and photonic projects at the SD Science and Engineering Fair.