A study published October 13 in Optics Express reports that a custom-mixed LED spectrum rated only 80 CRI helped participants in their 70s and 80s sort colors more accurately than a simulated D50 daylight reference rated Ra 97. The result, from a Fudan University team in Shanghai, rests on an argument about how color metrics are calculated rather than on the 80 figure itself: the spectrum was tuned for eyes that have yellowed with age.
The eye's lens yellows over time and filters short-wavelength light. Ra and TM-30, the metrics specifiers actually use, are computed with a fixed standard observer that makes no allowance for lens aging, even though the CIE's 2006 physiological model includes an age parameter. The paper's eight authors, two of them Opple Lighting employees, modeled the color response of the aging eye and derived two metrics: one estimates how much of the color discrimination an older viewer has lost a given spectrum recovers, and the other measures color fidelity against the perception of a 32-year-old.
From 11,541 candidates to two spectra
The team screened 11,541 candidate spectra from a 16-channel LED luminaire, all at 5000 K with Ra of at least 80. Two were carried forward for testing against a D50 daylight reference with Ra 97. P1 prioritized color discrimination at Ra 80; P2 balanced discrimination and fidelity at Ra 90. When the authors re-ranked every candidate using the conventional standard observer, P1 lost its top position, showing that the spec-sheet favorite and the aging eye's favorite can be different lights.
Test results at 300 lux
Thirty-four participants aged 70 and older, with a mean age of 81.7, sorted colored caps from the Farnsworth-Munsell 100 Hue test in a viewing booth at 300 lux. Mean error scores fell from 79.2 under the reference to 62.4 under P1 and 65.0 under P2; both drops were statistically significant, while the difference between the two optimized spectra was not. Color discrimination improved for 26 of 34 participants (76.5%) under P1 and 22 of 34 (64.7%) under P2.
Asked whether fruits and vegetables looked natural, 28 participants said yes under P1, against 26 under both the reference and P2. A two-person difference proves little, but it suggests the lower Ra cost P1 nothing in perceived naturalness.
Caveats and commercial context
- The sample was small, and people with advanced cataracts, glaucoma or macular degeneration were excluded, removing many of the residents a memory care designer lights for.
- Chromaticity between the reference and test lights was not perfectly matched, and the naturalness question was a simple yes or no.
- The authors warn against reading 300 lux as a recommendation.
- Opple financially supported the study, according to the paper's disclosures. The paper names no product, but a news release distributed through Optica, the journal's publisher, says Opple is working to translate the findings into lighting products. The underlying data is available only on request, so independent replication matters.
Deployment is a separate constraint. The method requires at least four independently controlled LED channels, and multichannel color-mixing fixtures rarely appear in a care facility bid. Most products sold as tunable in healthcare and senior living adjust color temperature across two channels, which would not reproduce these spectra. That gap is an interpretation rather than a claim in the paper.
For lighting people in senior living and healthcare, the pointed question is whose eyes the metric represents: the industry's color measures make no allowance for aging, while a growing share of building occupants are well past middle age. If a tuned spectrum can help a resident read a medication label or judge whether food has spoiled, the debate shifts to how quickly the evidence reaches specifications and product lines, and whose products get there first.