In senior living projects, an 80 CRI luminaire can invite questions. A study published Oct 13 in Optics Express offers a counterpoint: a custom-mixed LED spectrum rated at 80 CRI helped people in their 70s and 80s sort colors more accurately than a daylight reference rated at 97. The low CRI score was not the objective; the spectrum was adjusted for aging eyes.
The research comes from Fudan University in Shanghai. Two Opple Lighting employees are among its eight authors. It begins with a known physiological problem: the eye’s lens yellows with age and filters short-wavelength light. Ra and TM-30, the color metrics commonly used by specifiers, are calculated with a fixed standard observer that does not account for lens aging. The CIE’s 2006 physiological model does include an age parameter, but conventional specification practice does not.
Two metrics, two optimized spectra
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 the perception of a 32-year-old. The researchers screened 11,541 candidate spectra from a 16-channel LED luminaire, all at 5000 K and with Ra of at least 80.
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. When the authors re-ranked all candidates using the conventional standard observer, P1 lost its top position. That result is central: the spectrum favored by a spec sheet and the spectrum favored by an aging eye can be different.
What the participant test showed
The test involved participants aged 70 and older, with a mean age of 81.7. They 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 reductions were statistically significant. Color discrimination improved for 26 of 34 participants under P1, or 76.5%, and for 22 of 34 under P2, or 64.7%. The difference between the two optimized spectra was not statistically significant.
On perceived naturalness, 28 participants said fruits and vegetables looked natural under P1, compared with 26 under both the reference and P2. The authors note that a two-person difference proves little, but the result suggests that P1’s lower Ra did not cost it in perceived naturalness in this test.
The limits are part of the finding
The study has clear limits. The sample was small. People with advanced cataracts, glaucoma, or macular degeneration were excluded, removing many residents for whom memory care designers light spaces. Chromaticity between the reference and test lights was not perfectly matched. The naturalness question was a simple yes or no. The authors also warn against treating 300 lux as a recommendation.
Funding and replication also matter. The paper’s disclosures say Opple financially supported the study. 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 the work early product development as well as academic research. The underlying data is available only on request, so independent replication is important.
From laboratory spectrum to specification
The method 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. The publication explicitly identifies that gap as its own reading, not a claim in the paper. Even so, the hardware requirement is a practical barrier between a demonstrated spectrum and a commonly specified luminaire.
Why the metric gap matters
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, while 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.
The study does not establish a new standard, and it does not show that every senior living project should move to multichannel color mixing. It does show that an 80 CRI rating is not a complete description of visual performance for older viewers. A specifier reading only Ra could reject a spectrum that performed better in the tested task, while accepting a high-Ra reference that performed worse for the same group.
That is an uncomfortable result for a specification culture built around fixed observers and single-number ratings. The next step is not to treat P1 or P2 as catalog products. It is to ask which color metrics should be reported for aging populations, how those metrics are validated, and whether the hardware needed to deliver optimized spectra can fit care-facility bidding practices. The paper opens those questions; it does not close them.