Solid state lighting has made great advancements in the lighting field, but we still need to be attentive lighting quality and not get swept in by economic factors like cost & efficacy. Stroboscopic flicker has creeped back after it was eliminated from fluorescent lighting. Stroboscopic flicker what is it? How can we recognize it as designers and how do we decide where it is and is not acceptable (in architectural & automotive settings). We’ll present a few sample strobing rates for demonstration purposes. Presented by: Natalia Lesniak

2. Natalia Lesniak, Msc, LC, IES
Cooley Monato Studio

3. Credit(s) earned on completion of this course will be
reported to AIA CES for AIA members. Certificates of
Completion for both AIA members and non-AIA
members are available upon request.
This course is registered with AIA CES for
continuing professional education. As such, it does
not include content that may be deemed or
construed to be an approval or endorsement by the
AIA of any material of construction or any method or
manner of
handling, using, distributing, or dealing in any
material or product.
___________________________________________
Questions related to specific materials, methods, and services will
be addressed at the conclusion of this presentation.

4. Solid state lighting has made great advancements in the
lighting field, but we still need to be attentive lighting
quality and flicker. Stroboscopic flicker has creeped back.
How can we recognize it as designers and how do we
decide where it is and is not acceptable. How does it
impact our health and contribute to migraines?

5.  What is flicker & stroboscopic flicker
 Potential hazards from flicker
 What are the metrics used to determine flicker
 How to determine if a fixture has the potential of being
hazardous
 How light potentially contributes to/aggravates
photophobia & migraines

7. Flicker
● Modulation in light output over
time
Stroboscopic effect
● Luminous flux modulation,
perceived when objects are in
motion
Photo: Lighting Research Center

8. Visible Flicker
● Distraction
● Neurological Problems (Pokemon issus) Epileptic
seizure 1 in 4,000 have photosensitive epilepsy
(~3-~70Hz)
● Increased autistic behavior
Invisible Flicker (Stroboscopic flicker)
● Eyestrain, headache
● Migraine
● Stroboscopic effect (impacted motion perception)
● Reduced performance (reading or other visual
tasks)
● Disruption of security systems & security cameras
Photo: Lighting Research Center

9. Photo: Courtesy of the British Migraine Association
Source: Lawrence D. Goldberg, The Cost of Migraine and Its Treatment.
THE AMERICAN JOURNAL OF MANAGED CARE
Lipton RB et al Headache. 2001.
Over 28 million people afflict in the USA (age 12 & up)
21 million women
7 million men
1 in 125 sufferer from migraines
$13 billion estimated annual costs (direct & indirect)
• Emergency room visits
• Hospitalization
• Medication use
• Clinical visits
• Lost work days
• Pain of migraine sufferers

10. ● Exposure duration
● Area of retina getting stimulation
● Brightness of flash (higher contrast in
luminances
● Contrast of flash with surrounding
luminance (think brightness contrast)
so...higher contrast, intensity and longer
exposure makes it worse
Photo: Lighting Research CenterPhoto: Courtesy of the British Migraine Association

11. Photo: Gjon Mili, 1947, Stroboscopic image of ballerina Nora Kaye performing

12. Source: IES Lighting Handbook

13. Most lighting
systems operated
on AC mains
produce flicker
Source: DOE SSL TECHNOLOGY FACT SHEET: Flicker

14. Good
Bad

15. Source: DOE SSL TECHNOLOGY FACT SHEET: Flicker
Most lighting
systems operated
on AC mains
produce flicker

16. Source: Philips Lighting

17. • Driver
• Dimmer
• AC LEDs
• DC LEDs with poor drivers
• LED lamps on electronic
transformers
• Phase cut dimmers (triac)
• Pulse width modulation (PWM)
drivers
Photo: Lighting Research Center
(Excluding power issues)

18. Request waveform or flicker information
(missing from most cut sheets)
Review samples
• Move your hand or a pencil
• Flicker wheel
• Look at the source w/ a digital camera
Its more noticeable with higher contrast
(black object on white back ground)
Photo: Lighting Research Center

19. Test for product for:
•Flicker frequency in hz (must be greater than 100 hz)
•Determine % Flicker
•Multiply the frequency by 0.08 and round up to the nearest whole
number to get the max Allowable % Flicker
If % Flicker is LOWER than the Allowable Flicker, then the
product is acceptable for all but the most unusually
sensitive individuals.
If frequency is difficult to determine, % Flicker shall not
exceed 10%.
120 Hz x 0.08=9.6, thus MAX Allowed % Flicker is 10%

20. What to look for:
•Flicker Freq ≥ 100 Hz
•% Flicker ≤ Flicker Freq x 0.08 (normal populations), or
•% Flicker ≤ Flicker Freq x 0.0333 (special populations)
Recap:
120 Hz x 0.08=9.6, thus MAX Allowed % Flicker is 10%
•% Flicker shall NOT exceed 10%.

21. Acceptable
Not Acceptable

22. ● 1789-2015 IEEE Recommended Practices for Modulating Current in
High-Brightness LEDs for Mitigating Health Risks to Viewers
(available since June 2015)
● IES Lighting Handbook
● ASSIST: Application Considerations Related to Stroboscopic Effects
from Light Source Flicker
http://www.lrc.rpi.edu/programs/solidstate/assist/pdf/AR-FlickerApps.pdf

23. • Industrial spaces (rotating machinery)
• Hospitals
• Offices/classrooms
• Video conferencing/filming studios/security camera

24. • Places with limited/no motion (object/art lighting,
accent or peripheral lighting where there the main
light sources are free of stroboscopic flicker)
• Use good judgement

25. Source: H. Kolb. 2003, http://www.ledc.co.uk/oct.htm

26. Source: Dacey, 2005
Melanopsin expressing
retinal ganglion cells
(found in humans in
2001)
Vertebrate melanopsin
gene – Opn4m

27. Light-induced discomfort and pain
in migraine (Vanagaite 1997)
88% of patients experience
photophobia during
migraines
Over 50% of migraine
sufferers find that a light
stimulus have induced
migraine attacks

28. Source: Nosada, 2010; Z. Molnar 2010
ipRGCs innervate
nociceptive neurons in
posterior thalmus (Po)
Spinal trigeminal
neurons innervate Po
nociceptive neurons
Po projects to
visual cortex
Meninges

29. • Visual phenomena (various shapes, bright spots or flashes of light)
• Vision loss
• Pins and needles sensations in an arm or leg
• Speech or language problems (aphasia)
• Pain on one side or both sides of your head
• Pain that has a pulsating, throbbing quality
• Sensitivity to light, sounds and sometimes smells
• Lightheadedness, sometimes followed by fainting
• Nausea and vomiting
• Blurred vision
Source: Mayo Clinic

30. Model of how light may
contribute to the neural
mechanism in exacerbating
migraines (Noseda 2010)
Source: A neural mechanism for exacerbation of headache by light Nature Neuroscience 13, 239–245 (2010)
Electrode recordings

31. Thank You!

32. This concludes The American Institute of Architects
Continuing Education Systems Course