The U.S. Department of Energy (DOE) has published the first in a series of four special investigations intended to extend the findings of CALiPER Application Summary Report 20: LED PAR38 Lamps, which was published late last year. The new report, CALiPER Report 20.1: Subjective Evaluation of Beam Quality, Shadow Quality, and Color Quality for LED PAR38 Lamps, focuses on a subset of the lamps from Report 20, which were separately assessed by members of the Illuminating Engineering Society of North America.
The results suggest that many of the LED products compared favorably to halogen benchmarks in all attributes considered. LED lamps using a single-emitter design were generally preferred for their beam quality and shadow quality, and the ranking of color quality did not always match the rank-order according to the product’s color rendering index (CRI).
Other key findings:
* Poor color consistency within the beam, and stray light outside the main beam pattern, were the attributes most likely to be noted by the observers as negative features.
* LED lamps with narrow-spot distributions were generally viewed as having less-acceptable beam quality than their narrow-flood or flood counterparts, although there was substantial variation in perceived quality within any of the groups.
* For color quality, the observers generally preferred 3000K LED lamps over 2700K LED lamps.
Although many of the LED PAR38 lamps were ranked higher than the halogen benchmarks, there is room for improvement for even the best-performing lamps. Furthermore, there remains substantial variability among LED PAR38 lamps—as was also seen among halogen lamps—which will require buyers to make careful purchases.
The report is available online here.
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