What the accuracy numbers actually measure
When researchers talk about accuracy in circadian lighting, they are usually measuring how well a simulation or a sensor predicts the light that actually reaches the eye or skin. In one calibrated office simulation, the simulated and measured light spectra were highly correlated, and the error in the melanopic-to-photopic ratio—a key metric for circadian effectiveness—was under 4%, with a residual deviation within 7% [1]. Corneal illuminance and circadian stimulus had larger errors, within 10% and 20% respectively [1].
A separate measurement framework for spatially resolved light assessment reported relative errors of about 3–6% when compared with standard spectral radiometry [2]. An adaptive lighting design study reported simulation accuracy within a 10% error margin [5]. These numbers describe how closely a model or device reproduces a physical light measurement. They say nothing about whether a worker feels more productive or actually makes fewer errors on a task.
Perceived productivity is a different question from lighting accuracy
Perceived productivity is a subjective judgment—how alert, comfortable, or effective a person feels. One office lighting survey used questionnaires and rating scales to assess alertness, comfort, satisfaction, and performance alongside objective measurements of illuminance and color temperature [3]. That study found that natural light availability and higher color temperature were associated with better alertness, visual comfort, and satisfaction [3]. But it did not specifically test circadian-friendly lighting, and it did not compare subjective productivity ratings with any objective error or accuracy measure.
None of the accuracy-focused studies asked workers how productive they felt [1][2][5]. Conversely, the survey study did not report objective task accuracy or error rates that could be lined up against the subjective ratings [3]. So the two sides of the question—perceived gains and objective accuracy—have been studied in separate contexts, not head-to-head.
Why the gap matters for judging circadian-friendly lighting
A lighting system can be technically accurate—delivering the intended circadian stimulus within a few percent—without necessarily making people feel more productive or actually reducing their errors. The accuracy studies show that engineers can predict and control circadian-effective light with reasonable precision [1][2][5]. But precision in light delivery is not the same as a productivity benefit.
The one study that links lighting to alertness and satisfaction used subjective ratings and did not isolate circadian-friendly design from other lighting factors like natural light and color temperature [3]. That means we cannot say from these studies whether a perceived productivity gain would track with, exceed, or fall short of the objective accuracy of the lighting system. The comparison the question asks for has not been made in the evidence available.
Sources used in this answer
Improving the accuracy of circadian lighting simulation with field measurement
A calibrated circadian lighting simulation achieved high spectral correlation and errors under 4% for the melanopic/photopic ratio, with corneal illuminance and circadian stimulus errors within 10% and 20%, respectively.
Measurement of Circadian Effectiveness in Lighting for Office Applications
A spatially resolved light measurement framework for office lighting reported relative errors of about 3–6% compared with standard spectral radiometry.
Subjective and objective survey of office lighting: effects on alertness, comfort, satisfaction, and safety
An office lighting survey found that natural light availability and higher color temperature were associated with improved alertness, visual comfort, satisfaction, and worker preference, based on subjective ratings.
Evaluation of wearable light dosimeters for circadian lighting: spectral, spatial, photometric, melanopic, and thermal performance
Among three wearable light dosimeters tested against a calibrated spectroradiometer, the Blue Iris Speck had the highest photometric and data-logging accuracy, while the Actiwatch had the poorest photometric performance.
Intelligent Lighting Space Design with 3D Modeling and Adaptive Control for Optimizing Circadian Rhythm Based on WELL Standards
An adaptive circadian lighting design study reported simulation accuracy within a 10% error margin for maintaining target illuminance and equivalent melanopic lux.