The U.S. Department of Energy recently released the first in a series of follow-up studies on PAR38 lamps as part of its CALiPER (Commercially Available LED Product Evaluation and Reporting) series of reports on solid-state lighting. Under the CALiPER program, DOE and volunteers from the Illumination Engineering Society (IES), run lighting products purchased at retail through a battery of tests to evaluate their performance compared to conventional light sources and the claims of the products’ manufacturers. The latest report is one of three planned follow-up studies on PAR 38 lamps, “Report 20.1: Subjective Evaluation of Beam Quality, Shadow Quality, and Color Quality for LED PAR38 Lamps.”
For this study, evaluators looked at a selection of the products purchased and evaluated in its “Application Summary Report 20: LED PAR38 Lamps” published last year and made measurements and subjective judgments regarding the products’ performance. The lamps were divided into three groups based on their beam type – spot lamps, narrow flood lamps and flood lamps – and the judges rated each one on beam quality, shadow quality and color quality compared with conventional halogen lamps.
Among their findings, the researchers found that the spot lamps had the least acceptable beam quality, with 38% of the ratings falling in the “unacceptable” category. The narrow flood lamps satisfied the judges more. The two top-ranked products in that category used single-emitter designs and were given outstanding or acceptable ratings by all the observers. The products rated unacceptable were typically faulted for stray light outside the beam. The flood lamps that were considered unacceptable typically had problems with color consistency or brightness consistency within the beam pattern.
In its overall discussion, the researchers found patterns across the three lamp types in that single-emitter designs were almost unanimously favored, and that particularly in spot lamps, LEDs still have some development ahead before they achieve their full potential. At least two lamps in each category were rated higher than their halogen counterparts. “Given the markedly higher efficacy of LED PAR38 lamps, those with better beam quality than the halogen lamps have a multifaceted advantage for retrofit applications or new construction,” the report concluded.
DOE said subsequent reports will cover flicker, dimming and power quality characteristics; stress testing; and lumen and chromaticity maintenance.