Pillar II · Neurological Stability · IEEE 1789-2015

The Light You Can't See
Is Still Stressing Your Brain

Every LED in your home almost certainly flickers. Not visibly — at frequencies your conscious vision cannot detect. But "invisible" does not mean "without effect." The neurological research behind IEEE 1789-2015 documents measurable stress responses, photosensitive seizure risk, and headache provocation from temporal light modulation that operates entirely below the threshold of awareness. This page explains exactly what flicker is, how to measure it, what the standard actually says, and what hardware eliminates it.

IEEE 1789-2015 Standard CIE TN 006:2016 Flicker Metrology Wilkins et al. — Visual Stress Research PREA / IES RP-1-12
On This Page
Fundamentals · LED Physics · Why Every LED Flickers

What Flicker Actually Is — And Why Every LED Is Born Flickering

Flicker is not a defect in cheap LEDs. It is a physical consequence of how LEDs produce light. Understanding why it happens at the hardware level is the prerequisite for understanding why the solution requires a specific driver architecture — not a different bulb.

An LED — a Light Emitting Diode — produces light only when current flows through it in the forward direction. Its light output is directly and immediately proportional to the current flowing through it at that instant. There is essentially zero latency between current and photon output. This is fundamentally different from incandescent bulbs, whose tungsten filament stores thermal energy and therefore averages out small current fluctuations — a natural low-pass filter.

The electrical supply entering your home is 120V AC in North America (230V AC in Europe) — alternating current that reverses direction 60 times per second (50Hz in Europe). To power an LED, this AC must be converted to DC and regulated to the correct current level. Every step of that conversion process can introduce temporal current variations. If the driver does not smooth those variations to near-zero, the LED output modulates at the same frequencies — and you have flicker.

The three most common sources of residential LED flicker:

1. Mains ripple at 100/120Hz. Cheap LED drivers that do not include adequate filtering capacitance allow the 100Hz (or 120Hz in North America) ripple from the AC rectification to modulate the LED current directly. This produces 100Hz flicker — the most common form in low-cost retrofit bulbs.

2. PWM dimming. Pulse-width modulation is the dominant dimming architecture in consumer LED products because it is cheap and preserves color consistency. A PWM dimmer switches the LED fully on and fully off at a set frequency, varying the ratio of on-time to off-time to control perceived brightness. At 50% dim on a 500Hz PWM driver, the LED is off for 1ms, on for 1ms, off for 1ms — 500 times per second. This is 100% modulation depth at 500Hz. No flicker meter in existence rates this as safe.

3. Resonance and switching artifacts. Switch-mode power supply circuitry in LED drivers operates at high frequencies (typically 50–500kHz) but can produce sub-harmonic and intermodulation flicker at audible and near-audible frequencies (200Hz–2kHz) depending on the quality of the filtering design.

The Critical Insight

The waveform above shows what "50% dim" actually means in each architecture. The PWM driver switches the LED completely off and completely on 500 times per second. The light output is binary — full brightness or zero — even though it appears half-bright to a casual observer. The constant-current driver reduces the actual current through the LED, producing genuinely continuous 50% output with only minor electrical ripple. These two methods produce identical perceived brightness at normal viewing. Their neurological impact is not identical.

100Hz
Flicker frequency from cheap mains-connected LED bulbs — most common residential failure mode
IES TM-24-12 · CIE TN 006
100%
Modulation depth of a PWM-dimmed LED at any dim level — fully off to fully on, every cycle
IEEE 1789-2015 basis
~3%
Typical modulation depth of a well-designed constant-current driver at 50% output
LumeCircadian driver specification
0
LED thermal inertia — unlike incandescent, LEDs have no filament mass to average out current ripple
Fundamental LED physics
Metrology · Percent Flicker · Flicker Index · How to Measure

Percent Flicker — The Two Numbers Every Lighting Spec Must Include

There are two distinct quantitative measures of flicker. Most discussions use only one — percent flicker — and ignore the second, flicker index. Both are necessary because they capture different aspects of the waveform's potential for biological impact. Neither alone is sufficient for a complete specification.

Why you need both numbers: Percent flicker tells you the depth of modulation — how much the light swings between its maximum and minimum output. Flicker Index tells you the shape of that swing. A source that spends most of its time at low output and briefly spikes to high output has a high flicker index even if its percent flicker appears moderate. Both waveform characteristics contribute to biological impact.

The most commonly misunderstood flicker scenario is a PWM-dimmed LED at a low dim level — say, 10% output. The light appears very dim and comfortable. Percent flicker is still 100% (the LED is still switching fully on and fully off). But the flicker index is now approximately 0.90 — the LED is off for 90% of every cycle and on for only 10%. The brief intense flash at 10% duty cycle is, per-flash, at full LED brightness. This is a more neurologically provocative waveform than 50% PWM dimming at the same frequency, not less.

This is the reason smart home "dim warm" settings that reduce brightness via PWM do not reduce flicker risk. Dimming a PWM source makes its flicker index worse, not better. The only way to reduce flicker is to change the driver architecture or to use a driver operating at a high enough frequency that the biological response systems cannot track it.

The Dimming Trap — What Most Guides Get Wrong

Telling someone to "dim their lights to reduce flicker" is one of the most common pieces of incorrect lighting advice in circulation. For PWM-driven sources — which describes the majority of consumer LED dimmers and smart bulbs — dimming maintains 100% modulation depth and worsens flicker index. The correct advice is: identify whether your dimmer uses PWM or current reduction, and if PWM, replace the driver rather than adjusting the dim level.

IEEE 1789-2015 · Risk Zone Definitions · Field Application

IEEE 1789-2015 — The Three Risk Zones Decoded

IEEE 1789-2015 is the only widely cited engineering standard for LED flicker health risk. Most references mention it without explaining how it works. The standard defines three risk zones that are functions of both frequency and modulation depth simultaneously — not frequency alone or modulation depth alone.

✓ Low Risk
No Observable Effects
M% ≤ 0.08 × f (Hz)
At this combination of frequency and modulation, the IEEE working group found no documented neurological or visual adverse effects in the surveyed literature. This is the target zone for health-sensitive environments.
At 1000Hz: M% must be ≤ 8% ✓
At 400Hz: M% must be ≤ 3.2% ✓
At 100Hz: M% must be ≤ 0.8% — very hard to achieve
⚠ Caution
Acceptable with Caution
0.08×f < M% ≤ 0.16×f
The caution zone represents a range where adverse effects become possible for sensitive subpopulations. Photosensitive individuals, migraine sufferers, and those with certain neurological conditions may be affected even when the general population is not.
At 1000Hz: M% between 8–16% → Caution
At 400Hz: M% between 3.2–6.4% → Caution
At 100Hz: M% between 0.8–1.6% → Caution
✕ High Risk
Observable Effects Possible
M% > 0.16 × f (Hz)
Above this threshold, the working group identified documented cases of adverse neurological effects in the general population including headache, eyestrain, and in the most severe cases photosensitive seizure provocation for susceptible individuals.
At 1000Hz: M% > 16% → High Risk
At 400Hz: M% > 6.4% → High Risk
At 100Hz: M% > 1.6% → High Risk
PWM at any frequency: M% = 100% → Always High Risk
How to Read the Risk Zone Chart

Every LED driver in every product can be plotted as a single point on this chart. Find the driver's PWM frequency on the horizontal axis and its modulation percentage on the vertical axis. Points below the green line are Low Risk. Points between the green and red lines are Caution. Points above the red line — which includes every standard PWM-dimmed LED at frequencies below approximately 600Hz — are High Risk. The chart makes visible what years of "just use warm light" advice obscures: the majority of residential dimmers, smart bulbs, and nightlights plot in the top-left High Risk quadrant regardless of their color temperature.

Neuroscience · Biological Mechanisms · Why It Matters Below Awareness

How Flicker Stresses the Nervous System — Four Distinct Pathways

"You can't see it so it can't affect you" is the most persistent myth in flicker science. There are at least four documented neurological pathways through which sub-perceptual temporal light modulation produces measurable biological responses — none of which require conscious flicker perception.

◈
Cortical Entrainment (Visual Cortex Driving)
The primary visual cortex responds to temporal modulation in light through a phenomenon called steady-state visual evoked potentials (SSVEP). When a flickering light stimulus is presented — even below conscious perception — the visual cortex generates neural oscillations at the same frequency. These entrained oscillations have been measured by EEG at modulation frequencies up to 80–100Hz. At certain frequencies that coincide with natural cortical rhythms (particularly the alpha band at 8–12Hz and beta band at 15–25Hz), cortical driving can be particularly pronounced. Critically, the visual cortex responds to temporal light modulation whether or not the person consciously detects it.
Measurable SSVEP: up to ~100Hz · Most pronounced: 8–25Hz
◈
Stroboscopic Effect on Moving Objects
Even when flicker is not visible in a steady scene, it becomes apparent when objects move across the field of view — a phenomenon called the stroboscopic effect or phantom array effect. At 100Hz mains-frequency flicker, a moving hand or rotating machinery appears to occupy multiple positions simultaneously. In industrial settings, this creates genuine safety hazards — rotating machinery can appear stationary under 100Hz lighting at certain speeds. In residential settings, the effect contributes to visual fatigue from the continuous unconscious processing of motion-discontinuity signals that the visual system must resolve.
Relevant range: 80–300Hz · Industrial safety concern from ~50Hz upward
◈
Photosensitive Seizure Threshold
Photosensitive epilepsy affects approximately 1 in 4,000 people in the general population — with seizure threshold highest for flash rates between 15–25Hz. This range is the most dangerous, corresponding to the gamma-frequency threshold of cortical excitability. IEEE 1789-2015 cites this as a primary justification for its risk zones. The standard does not claim that residential LEDs typically flicker at 15–25Hz — most flicker at 100Hz or higher — but the conservative risk framework accounts for partial harmonics, power line frequency interactions, and the fact that sensitive individuals can respond to a broader frequency range than the general population.
Peak risk: 15–25Hz · IEC 60601 / Harding standard for photosensitive epilepsy
◈
Cumulative Visual Fatigue and Headache
The most common and practically significant effect documented in the IEEE working group literature is increased visual fatigue, eye strain, and headache prevalence among populations exposed to high-modulation light sources for extended durations. The mechanism is not fully resolved but involves sustained high-frequency processing demand on the magnocellular visual pathway, which is highly sensitive to temporal luminance changes. Research by Wilkins et al. at the University of Essex documented statistically significant increases in headache and visual discomfort under fluorescent lighting with high flicker — findings that translate directly to modern PWM-dimmed LEDs operating at comparable modulation profiles.
Documented: extended exposure to M% > 25% at 100–200Hz · Migraine sufferers: lower threshold
The Migraine Population — A Quantified Sensitivity Gap

Migraine affects approximately 12% of the general population and is characterized in part by cortical hyperexcitability — an abnormally amplified response to sensory stimuli including light. Research by Wilkins, Marcus, and others documents that migraine sufferers show measurable discomfort responses to temporal light modulation at modulation depths and frequencies that produce no measurable response in non-migraineurs. The IEEE 1789 Low Risk boundary provides a reasonable general population threshold. For a household with a migraine sufferer, the correct specification is not the general Low Risk limit but the most conservative achievable — which is constant-current drive with sub-1% ripple. This distinction has practical hardware consequences for the 1 in 8 households where migraine is present.

Driver Architecture · PWM vs. CC · The Engineering Decision

PWM vs. Constant-Current — Why the Architecture Matters More Than the Frequency

The LED driver is the component that determines flicker — not the LED emitter, not the fixture housing, and not the bulb. Every PWM driver produces flicker by design. Every constant-current driver with adequate ripple filtering produces negligible flicker by design. The choice between these architectures is the single most consequential decision in a flicker-safe lighting installation.

Architecture A — Flicker Risk
Pulse-Width Modulation (PWM)

PWM dimming works by switching the LED completely on and completely off at a fixed frequency. The ratio of on-time to total cycle time — the duty cycle — determines perceived brightness. At 50% dim, the LED is on for half of every cycle and off for the other half.

Why manufacturers choose it: PWM is electrically simple, cheap to implement, and preserves LED color consistency across dim levels because the LED always operates at full drive current when on — the color point of an LED shifts with drive current, so always running at full current avoids color shift during dimming.

Why it fails the health standard: Modulation depth is always 100% regardless of dim level or frequency. At any PWM frequency below approximately 1250Hz, modulation depth of 100% places the source in the High Risk zone of IEEE 1789-2015. At typical residential PWM frequencies of 200–500Hz, the operating point is well inside the High Risk zone.

Modulation depth: always 100% (Lmin = 0) IEEE 1789 compliance at ≤500Hz: impossible IEEE 1789 Low Risk requires: f ≥ 1250Hz for 100% modulation Typical residential PWM: 200–500Hz → High Risk at all dim levels
Architecture B — Flicker Safe
Constant-Current (CC) Drive

Constant-current dimming adjusts brightness by changing the magnitude of the continuous DC current flowing through the LED. At 50% dim, the driver outputs half the rated current continuously. There are no switching events, no on/off cycles, and no PWM modulation at audible or near-audible frequencies.

The residual ripple question: No real power supply outputs perfectly smooth DC. Switch-mode CC drivers operate their power conversion stage at high frequencies (typically 50–500kHz) and produce a residual AC component — ripple — superimposed on the DC output. Well-designed CC drivers achieve ripple below 2–5%, which at their operating frequencies (above 50kHz) places them comfortably in the IEEE 1789 Low Risk zone.

The color shift tradeoff: The one legitimate disadvantage of CC dimming is that LED color point shifts as drive current decreases — a warm-shift in phosphor-converted LEDs at low currents. For circadian amber emitters this is inconsequential. For white LED systems, the color shift must be managed in the driver specification or accepted as a design characteristic.

Modulation depth: typically 1–5% at output ripple frequencies Operating frequency of residual ripple: 50kHz–500kHz IEEE 1789 compliance: achieved at standard ripple levels LumeCircadian target: <3% modulation at all dim levels
Hybrid Architecture: High-Frequency PWM

A third architecture deserves mention: high-frequency PWM, operating above approximately 2–4kHz. At these frequencies, even 100% modulation depth can meet the IEEE 1789 Low Risk threshold (at 4000Hz: Low Risk requires M% ≤ 32%, which 100% exceeds — but at 4kHz the biological response systems are significantly attenuated). Some high-quality LED drivers use PWM at 4kHz or above to preserve color consistency while reducing flicker risk. This is a valid approach but requires careful verification — many products marketed as "high-frequency PWM" operate at 1–2kHz, which still does not meet the Low Risk limit at 100% modulation depth. For infant environments and migraine-sensitive households, constant-current remains the preferred specification regardless of PWM frequency.

Real-World Data · Product Categories · What You Actually Have at Home

Real-World Flicker in Common Products — The Numbers Behind the Marketing Claims

Published flicker measurement studies and independent testing reveal a consistent pattern: the most heavily marketed "smart" and "circadian-friendly" residential lighting products are among the worst performers on flicker metrics. Here is the landscape organized by product category.

Flicker Compliance Summary by Product Category — IEEE 1789-2015 Assessment
Product Category Typical Architecture PWM Frequency Modulation % IEEE 1789 Zone Health-Sensitive Use
Cheap A19 retrofit (no dimmer) Capacitor-drop / mains ripple 100–120Hz 60–85% High Risk Disqualified
Smart bulbs (Philips Hue, LIFX etc.) on dim PWM dimming 200–500Hz 100% High Risk Disqualified
LED strip + consumer PWM controller PWM dimming 200–1000Hz 100% High Risk Disqualified
TRIAC dimmer + compatible LED TRIAC phase-cut → PWM 100–120Hz 70–95% High Risk Disqualified
LED driver, PWM at 4kHz+ High-freq PWM 4000Hz+ 100% Caution General pop. only
Quality CC driver, properly specified Constant-current N/A (DC ripple) 2–5% Low Risk ✓ All populations
LumeCircadian CC specification Constant-current N/A (<3% ripple) <3% Low Risk ✓ All — incl. infant
The Smart Bulb Problem — What the Marketing Doesn't Say

Premium smart bulbs marketed as "circadian" or "sleep-friendly" — including widely sold products in the Philips Hue, LIFX, and similar ecosystems — use PWM dimming architectures operating at frequencies between 200–500Hz. When dimmed, they produce 100% modulation depth at those frequencies, placing them firmly in the IEEE 1789-2015 High Risk zone. The "warm amber" color mode reduces melanopic stimulation — a genuine benefit on the circadian axis. It does nothing whatsoever for flicker. A warm-amber PWM-dimmed smart bulb at 10pm is a circadian improvement over a cool-white version but a neurological problem at the same time. Circadian compliance and flicker compliance are independent axes. Both must be checked.

Clinical Application · Migraine · Photosensitivity Protocol

Migraine-Safe Lighting Protocol — A Step-by-Step Implementation Guide

Migraine-safe lighting requires meeting two independent specifications simultaneously: zero blue-light stimulation during night hours (the circadian axis) and zero meaningful flicker at all hours (the neurological axis). Both must be implemented. Neither alone is sufficient for a migraine-sensitive household.

Day — Flicker Standard
< 3%
At all dim levels, all day. CC driver. No PWM below 4kHz.
Night — Spectral Target
590nm+
M/P ≤ 0.02. Verified narrow-band amber. Not filtered white.
Night — Flicker Target
< 1%
More conservative than general Low Risk. CC driver, quality grade.
Transition Timing
2hr pre-sleep
Switch to amber at least 2 hours before target sleep time, not just at bedtime.
Screen Blue-Block
Required
All screens must use hardware amber filter or software blue-block (f.lux/Night Shift) during amber period.
Emergency Lighting
Red LED
Torch, nightlight fallback: deep red emitter (625nm+) only. No white light under any circumstances during migraine episode.
01
Audit Every Dimmer and Driver in the Home

Before purchasing anything, identify the dimming architecture of every fixture. Check whether your current dimmers are TRIAC (phase-cut) types — which produce 100–120Hz heavy flicker on most LED loads — or whether your smart bulbs use PWM. For every product, find the driver datasheet or contact the manufacturer to determine PWM frequency. If the answer is not publicly documented, assume PWM and treat as non-compliant.

Tool: smartphone camera slow-motion video (see §8) can reveal 100–200Hz flicker without specialist equipment
02
Replace Dimmers First, Fixtures Second

The most common and cost-effective upgrade path is replacing PWM-based dimmers with constant-current LED drivers at the fixture level. This matters more than replacing the LED emitter itself — a good emitter on a bad driver will still flicker. A mediocre emitter on a quality CC driver will not. Prioritize the rooms where the migraine-affected person spends the most time at low light levels: bedrooms, living areas used in the evening, and bathrooms used for night routines.

Priority order: bedroom (8+ hours/night) → living area (evening use) → bathroom → other
03
Install Dedicated Amber Night Circuit — Fully Separate from Day Circuit

The night-time amber circuit must be electrically and physically separate from the daytime white-light circuit. This is not a dimmed version of the daytime fixture — it is a different emitter, different driver, and ideally different fixture position (lower mounting height, task-oriented placement rather than overhead flood). Integrating both functions into a single "tunable white" fixture with CCT-shift capability introduces reliability and spectral verification complexity. Separate circuits eliminate the risk of the daytime channel accidentally activating during the amber window.

Specification: 590nm+ emitter · CC driver · 5–15 lux task plane · Separate switch from day circuit
04
Extend the Amber Window — Start Earlier Than You Think

Most guidance on evening light transition focuses on bedtime. For migraine-sensitive individuals, the amber transition should begin at least two hours before target sleep time, and ideally at sunset or local dusk. The rationale is twofold: melatonin onset requires sustained low-melanopic-EDI conditions over time, not just immediately before sleep; and migraine triggers are cumulative — a full evening of moderate blue-light and flicker exposure before a late amber switch may have already initiated a cortical sensitization cascade that the ambient switch cannot reverse.

Minimum: amber on 2hr before target sleep · Preferred: amber on at sunset · All screens covered
05
Verify with Measurement — Not by Appearance

A light source that appears amber can still fail the M/P specification if it is a filtered white source with residual blue output. A driver that appears to run smoothly can still produce high-frequency flicker invisible to any photographic method. The only way to confirm compliance is with spectral measurement (spectroradiometer or M/P-validated meter) for the circadian axis and a dedicated flicker meter or oscilloscope-based measurement for the neurological axis. For migraine-sensitive environments, visual confirmation is not sufficient.

Tools: spectroradiometer for M/P · Flicker meter or oscilloscope for IEEE 1789 compliance verification
Field Testing · DIY Methods · What Each Tool Can and Cannot Tell You

How to Test Your Own Lights — Three Methods, Honest Limitations

You can screen for LED flicker without any specialist equipment using your smartphone. But understanding what each method can and cannot detect is as important as knowing how to perform it — each technique has a specific frequency range within which it is useful and a range within which it is blind.

Method 1 — Smartphone camera slow-motion video. Film the light source in slow-motion mode (240fps or higher if available). Play back at normal speed. If you see the light visibly pulsing or darkening rhythmically, the flicker frequency is below approximately 120Hz (half the slow-motion frame rate). Most 100Hz mains-ripple flicker in cheap LED bulbs is clearly visible using this method.

Limitation: This method only detects flicker below roughly half the camera's frame rate. At 240fps, you can detect flicker below 120Hz. PWM at 500Hz will not be visible. Most smart bulb and dimmer PWM flicker (200–500Hz) is invisible to this method. A bulb that passes the slow-motion test may still be a PWM High Risk source.

Method 2 — Pencil/hand wave test. Wave your hand rapidly in front of the light. Under a high-flicker source, your hand will appear to leave multiple distinct shadow images — a stroboscopic trail. Under a low-flicker source, the hand motion appears smooth and continuous. This method is sensitive to flicker at frequencies roughly in the 60–300Hz range.

Limitation: Very subjective and sensitivity varies between individuals. Cannot distinguish 100Hz from 200Hz. Cannot detect flicker above approximately 300Hz. Should be used only as a rough screen, not a compliance test.

Method 3 — Dedicated flicker meter. Instruments such as the Gigahertz-Optik MSC15, UPRtek MK350S+, or similar spectroradiometers with flicker measurement capability provide quantitative percent flicker and flicker index measurements traceable to IES TM-24-12 and CIE TN 006. This is the only method that provides data sufficient for IEEE 1789-2015 compliance assessment.

Cost range: Entry-level dedicated flicker meters start around $150–300. Research-grade instruments with full spectral data cost $3,000–15,000. For most residential applications, a mid-range instrument at $300–600 provides sufficient precision for driver qualification and compliance screening.

Field Test Method Capability Comparison
Method Detectable Range Quantitative? Cost IEEE 1789 Valid?
Slow-motion video (240fps) <120Hz only No — visual only $0 (smartphone) No
Hand/pencil wave test ~60–300Hz No — subjective $0 No
Smartphone flicker apps <camera fps ÷ 2 Approximate only $0–15 No
Entry flicker meter 0–10kHz Yes — % flicker $150–300 Partial
Spectroradiometer + flicker 0–50kHz+ Yes — full metrics $600–15,000 ✓ Full
The One Test That Cannot Be Faked

The most reliable non-instrument test for driver architecture is to check the driver datasheet, not test the light output. A manufacturer that publishes driver specifications including PWM frequency, modulation depth, and ripple current percentage has provided the data needed for IEEE 1789 assessment without any measurement required. A manufacturer that provides no driver specification data should be assumed to use low-frequency PWM. The absence of specification data is itself a specification failure for health-sensitive applications.

Flicker & Neuro · Full Article Index

Flicker & Neuro — Deep-Dive Articles

Each article provides complete technical depth on a specific aspect of flicker science, driver selection, or field measurement.

IEEE 1789 · Full Implementation
IEEE 1789-2015: Field Implementation Guide
Complete worked examples for plotting any driver on the IEEE 1789 risk map, with frequency and modulation data from 30 common products.
Read Article →
Driver Architecture · Deep Dive
PWM vs. Constant-Current Dimming
Circuit-level explanation of both architectures, ripple current measurement, color shift tradeoffs, and a buyer's guide for CC driver selection.
Read Article →
Field Measurement · Protocol
Flicker Measurement Methods
Full protocol for measuring percent flicker, flicker index, and frequency using smartphone, entry meter, and spectroradiometer — with worked examples and interpretation guide.
Read Article →
Clinical Application · Migraine
Migraine-Safe Lighting Protocol
Full room-by-room implementation guide for migraine-sensitive households, including product vetting checklist, transition timing, and emergency lighting specification.
Read Article →
Related Pillars
Pillar I Foundation · Circadian Science
The Circadian Axis — Spectral Biology
The independent second hazard axis: melanopsin, M/P ratio, and why both flicker and spectrum must be specified together for complete neurological safety.
Circadian Science Hub →
Pillar I · Pediatric Shield
Flicker in the Infant Environment
Why the developing nervous system cannot rely on adult cortical filtering mechanisms — and why infant environments require the most conservative driver specifications.
Pediatric Shield →
Pillar III · HCL Retrofit
Specifying Drivers in Legacy Hardware
How to select and install CC drivers inside legacy Portfolio and other metal-housed fixtures — combining flicker safety with thermal longevity engineering.
HCL Retrofit →
Key References — This Page
  • IEEE Std 1789-2015. IEEE Recommended Practices for Modulating Current in High-Brightness LEDs for Mitigating Health Risks to Viewers. IEEE, New York, 2015.
  • CIE TN 006:2016. Visual Aspects of Time-Modulated Lighting Systems — Definitions and Measurement Models. Commission Internationale de l'Éclairage, 2016.
  • IES TM-24-12. Temporal Light Artifacts: Test Methods and Guidance for Acceptance Criteria. Illuminating Engineering Society, 2012.
  • Wilkins AJ, Veitch J, Lehman B. LED lighting flicker and potential health concerns: IEEE standard PAR1789 update. Proc. IEEE Energy Conversion Congress and Exposition. 2010:171–178.
  • Wilkins AJ. Visual Stress. Oxford University Press, 1995. (Foundational text on pattern/flicker-induced visual discomfort.)
  • Harding GFA, Jeavons PM. Photosensitive Epilepsy. Mac Keith Press, 1994.
  • Veitch JA, Martinsons C. Lighting Flicker, IEEE 1789, and the Practice of Lighting Design. Leukos. 2019;15(2-3):163–181. doi:10.1080/15502724.2018.1518715
  • Perz M, Vogels IMLC, Sekulovski D, Wang L, Tu Y, Heynderickx IEJ. Modeling the visibility of the stroboscopic effect occurring in temporally modulated light systems. Lighting Res. Technol. 2015;47(3):281–300.
  • Poplawski ME, Miller NE. Flicker in Solid-State Lighting: Measurement Techniques, and Proposed Reporting and Application Criteria. US DOE, 2013. DOE/EE-0868.