A study published Oct. 13 in Optics Express reports that a custom-mixed LED spectrum rated at just 80 CRI helped people in their 70s and 80s distinguish colors more accurately than a simulated daylight reference rated at 97. The low score was not the point. The spectrum was tuned for aging eyes.
The research comes from Fudan University in Shanghai, with two Opple Lighting employees among its eight authors. It starts from a well-known biological problem: the eye’s lens yellows with age and filters out more short-wavelength light. A spectrum that looks deficient by a conventional color metric can therefore be designed to compensate for the light older viewers actually receive. The study’s design tests whether a deliberately age-tuned spectrum can improve performance even when its nominal CRI is lower.
Ra and TM-30, the color metrics specifiers actually use, are calculated with a fixed standard observer that makes no allowance for lens aging. The CIE’s own 2006 physiological model includes an age parameter, but the common specification metrics do not.
The team modeled the color response of aging eyes and created two metrics. One estimates how much lost color discrimination a spectrum recovers for an older viewer. The other measures color fidelity against a 32-year-old’s perception. They screened 11,541 candidate spectra from a 16-channel LED luminaire, all at 5000 K and all with Ra of at least 80. The screen was broad enough to search for spectra that met both the color-temperature constraint and the minimum Ra threshold.
Two candidates were tested against a simulated D50 daylight reference with Ra of 97. P1 prioritized discrimination at Ra 80. P2 balanced discrimination and fidelity at Ra 90. Holding color temperature and the Ra floor constant narrowed the comparison to spectral shape within that design space.
When the authors re-ranked every candidate using the conventional standard observer, P1 lost its top position. The result does not invalidate Ra, but it shows that a ranking built on a fixed observer can point to a different winner when age is included. The spec-sheet favorite and the aging eye’s favorite can be different lights. That mismatch is central to the paper’s argument about specification.
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.
Color discrimination improved for 26 of 34 participants, or 76.5%, under P1 and for 22 of 34, or 64.7%, under P2. The gap between the two optimized spectra was not statistically significant, so the test does not establish a clear advantage for either tuned spectrum over the other. Both tuned spectra improved average scores, but the sample size limits subgroup conclusions.
Asked whether fruits and vegetables looked natural, 28 participants said yes under P1, compared with 26 under both the reference and P2. A two-person difference proves little, but it suggests that the lower Ra cost P1 nothing in perceived naturalness in this test.
The sample was small. People with advanced cataracts, glaucoma or macular degeneration were excluded, which removes many residents a memory-care designer lights for. That matters because the residents most likely to need help with color tasks may also be among those left out of the sample. Chromaticity between the reference and test lights was not perfectly matched, and the naturalness question was a simple yes or no. The authors also warn against reading 300 lux as a recommendation. That caution is important because the test illuminance was a laboratory condition, not a design target.
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. That makes this early product development as much as academic research.
The underlying data is available only on request, so independent replication matters. The paper names no commercial product, and the data are not openly posted. The method also requires at least four independently controlled LED channels.
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 of the study’s hardware requirement, not a claim in the paper.
For lighting people in senior living and healthcare, the study raises a pointed question. The industry’s color metrics make no allowance for aging eyes, and a growing share of building occupants are well past middle age. If a tuned spectrum can help residents read a medication label or judge whether food has spoiled, the debate shifts to how quickly that evidence reaches specifications and product lines, and whose products get there first. That is a supply-chain and standards question as much as a research question.