Andrea M. Wilkerson

Human perceptions of colour rendition vary with average fidelity, average gamut, and gamut shape

An experiment was conducted to evaluate how subjective impressions of a light source’s colour quality depend upon the details of the shifts it causes in the colour appearance of illuminated objects. Twenty-eight participants each evaluated 26 lighting conditions in a 3.1 m by 3.7 m room filled with objects selected to cover a range of hue, saturation, and lightness. IES TM-30-15 Fidelity Index (Rf) values ranged from 64 to 93, IES TM-30 Gamut Index (Rg) values ranging from 79 to 117, and IES TM-30 red chroma shift (Rcs,h1) values ranging from −19% to 26%. All lighting conditions had the same nominal illuminance and chromaticity. Participants were asked to rate each condition on eight point scales for saturated–dull, normal–shifted, and like–dislike, as well as classifying the condition as one of saturated, dull, normal, or shifted. The findings suggest that gamut shape is more important than average gamut area for modeling human preference, with red playing a more important role than other hues. Average fidelity alone is a weak predictor of human perception, especially CIE Ra. Nine of the top 12 rated products had a CIE Ra value of 73 or less, which indicates that the criteria of CIE Ra ≥ 80 may be excluding many preferred light sources.

Human perceptions of colour rendition at different chromaticities

An experiment was conducted to evaluate how perceptions of a light source’s colour quality depend upon colour rendition and chromaticity. Thirty-four participants each evaluated 50 lighting scenes in a 3.7 m by 5.5 m room filled with objects. The lighting scenes included five chromaticity groups, with 10 systematically-varied colour rendition conditions repeated in each group. Participants, who chromatically adapted to each chromaticity group, were asked to rate each scene on eight point scales for saturated-dull, normal-shifted and like–dislike (preference), as well as choosing whether they found the scenes to be acceptable or unacceptable. The findings suggest that colour rendition perceptions can vary with chromaticity, with an interactive effect of correlated colour temperature and Duv. The same IES TM-30-15 measures, Fidelity Index (IES Rf), Gamut Index (IES Rg) and hue-angle bin 16 (Red) Local Chroma Shift (IES Rcs,h16), could be used to effectively model perceptions within each chromaticity group, and provided suitable performance for the overall set of 50 conditions. The differences in ratings between the chromaticity groups were substantially smaller than the range in ratings for the 10 colour rendition conditions within each group, allowing the same acceptability-based criteria of IES Rf ≥ 75, IES Rg ≥ 98 and −7% ≤ IES Rcs,h16 ≤ 15% to be applied to all chromaticity groups.

Luminaire Dirt Depreciation (LDD): Field Data from Several Exterior Lighting Projects

ABSTRACT Luminaire dirt depreciation (LDD) data were evaluated for seven luminaires from three different project sites in Philadelphia, Pennsylvania, Minneapolis, Minnesota, and Yuma, Arizona. In each case, the luminaires were removed from the installation, carefully packaged and transported to a photometric testing laboratory, and then tested in the “as-is” or dirty condition, cleaned, and retested. In terms of light output, the results showed that the IES RP-36-15 method for estimating LDD was applicable to the light emitting diode (LED) luminaires evaluated. General claims of lower levels of dirt deprecation (or higher LDD values) for LED luminaires than for luminaires using conventional light sources were not supported by the test data for the LED luminaires in these three projects. Though the overall measured lumen depreciation due to accumulated dirt closely matched IES estimates for LDD, the data indicated that the accumulated dirt on the luminaires dramatically altered the luminous intensity distribution of the luminaires, with reductions in intensity of more than 25% at peak angles. These effects on luminous intensity distribution are not accounted for in IES LDD estimates.

Tuning the light in senior care: Evaluating a trial LED lighting system at the ACC Care Center in Sacramento, CA

This report summarizes the results from a trial installation of light-emitting diode (LED) lighting systems in several spaces within the ACC Care Center in Sacramento, CA. The Sacramento Municipal Utility District (SMUD) coordinated the project and invited the U.S. Department of Energy (DOE) to document the performance of the LED lighting systems as part of a GATEWAY evaluation. DOE tasked the Pacific Northwest National Laboratory (PNNL) to conduct the investigation. SMUD and ACC staff coordinated and completed the design and installation of the LED systems, while PNNL and SMUD staff evaluated the photometric performance of the systems. ACC staff also track behavioral and health measures of the residents; some of those results are reported here, although PNNL staff were not directly involved in collecting or interpreting those data. The trial installation took place in a double resident room and a single resident room, and the corridor that connects those (and other) rooms to the central nurse station. Other spaces in the trial included the nurse station, a common room called the family room located near the nurse station, and the ACC administrator’s private office.

Yuma Border Patrol Area Lighting Retrofit LED System Performance in a Trial Installation – Two Years Later

Documentation of the Yuma Sector Border Patrol Area lighting LED trial demonstration continues to provide a better understanding of LED technology performance in a high ambient temperature and high solar radiation environment. Measured data at the project site showed illuminances changing more rapidly than anticipated. As previously predicted, the causes for these observed changes are mostly if not completely explained by dirt accumulation. The laboratory measurements showed not only the effect of dirt on lumen output, but also on the distribution of light exiting the luminaire.

LED system performance in a trial installation - one year later: Yuma border patrol, Yuma, Arizona

The Yuma Sector Border Patrol Area is a high temperature and high solar radiation environment, providing an opportunity for the U.S. Department of Energy (DOE) to study thermal effects on outdoor light-emitting diode (LED) luminaires outside of the testing laboratory. Six LED luminaires were installed on three poles on the U.S.- Mexico border in February 2014 as part of a trial installation, which was detailed in a prior GATEWAY report.1 The initial trial installation was intended as a short - term test of six luminaires installed on three poles before proceeding with the complete installation of over 400 luminaires. Unexpected delays in the full installation have prevented the detailed evaluations initially planned, but the six installed LED luminaires continue to be monitored, and over the past year illuminance measurements were recorded initially in February 2014 and again in September 2014 at about 2500 hours of operation and in March 2015 at about 5000 hours of operation.

University of Maryland Wall Washer Retrofit - LED Modules Replace Halogen Lamps in a Performing Arts Center

The University of Maryland (UMD) began retrofitting halogen wall washers in the Clarice Smith Performing Arts Center (CSPAC) in April 2014. The U.S. Department of Energy (DOE) Solid-State Lighting (SSL) GATEWAY program documented this process through the final installation in March 2015, summarized in this report. The wall washers illuminate hallways lining the atrium, providing task illuminance for transitioning between spaces and visual interest to the atrium boundaries. The main goals of the retrofit were to maintain the visual appearance of the space while reducing maintenance costs – energy savings was considered an additional benefit by UMD Facilities Management. UMD Facilities Management is pleased with the results of this retrofit, and continues to initiate LED retrofit projects across the UMD campus.

LED Lighting in a Performing Arts Building at the University of Florida

The U.S. DOE GATEWAY Demonstration Program supports demonstrations of high-performance solid-state lighting (SSL) products in order to develop empirical data and experience with the in-the-field applications of this advanced lighting technology. This report describes the process and results of the 2013 - 2014 GATEWAY demonstration of SSL technology in the Nadine McGuire Theatre and Dance Pavilion at the University of Florida, Gainesville, FL. The LED solutions combined with dimming controls utilized in four interior spaces - the Acting Studio, Dance Studio, Scene Shop, and Dressing Room - received high marks from instructors, students/performers, and reduced energy use in all cases. The report discusses in depth and detail of each project area including specifications, energy savings, and user observations. The report concludes with lessons learned during the demonstration.

DOE CALiPER Program, Report 21.2: Linear (T8) LED Lamp Performance in Five Types of Recessed Troffers

Although lensed troffers are numerous, there are many other types of optical systems as well. This report looked at the performance of three linear (T8) LED lamps chosen primarily based on their luminous intensity distributions (narrow, medium, and wide beam angles) as well as a benchmark fluorescent lamp in five different troffer types. Also included are the results of a subjective evaluation. Results show that linear (T8) LED lamps can improve luminaire efficiency in K12-lensed and parabolic-louvered troffers, effect little change in volumetric and high-performance diffuse-lensed type luminaires, but reduce efficiency in recessed indirect troffers. These changes can be accompanied by visual appearance and visual comfort consequences, especially when LED lamps with clear lenses and narrow distributions are installed. Linear (T8) LED lamps with diffuse apertures exhibited wider beam angles, performed more similarly to fluorescent lamps, and received better ratings from observers. Guidance is provided on which luminaires are the best candidates for retrofitting with linear (T8) LED lamps.