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Stroboscopic Flicker


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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

Published in: Technology
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Stroboscopic Flicker

  1. 1. Natalia Lesniak, Msc, LC, IES Cooley Monato Studio
  2. 2. 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.
  3. 3. 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?
  4. 4.  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
  5. 5. Flicker ● Modulation in light output over time Stroboscopic effect ● Luminous flux modulation, perceived when objects are in motion Photo: Lighting Research Center
  6. 6. 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
  7. 7. 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
  8. 8. ● 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
  9. 9. Photo: Gjon Mili, 1947, Stroboscopic image of ballerina Nora Kaye performing
  10. 10. Source: IES Lighting Handbook
  11. 11. Most lighting systems operated on AC mains produce flicker Source: DOE SSL TECHNOLOGY FACT SHEET: Flicker
  12. 12. Good Bad
  13. 13. Source: DOE SSL TECHNOLOGY FACT SHEET: Flicker Most lighting systems operated on AC mains produce flicker
  14. 14. Source: Philips Lighting
  15. 15. • 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)
  16. 16. 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
  17. 17. 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%
  18. 18. 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%.
  19. 19. Acceptable Not Acceptable
  20. 20. ● 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
  21. 21. • Industrial spaces (rotating machinery) • Hospitals • Offices/classrooms • Video conferencing/filming studios/security camera
  22. 22. • 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
  23. 23. Source: H. Kolb. 2003,
  24. 24. Source: Dacey, 2005 Melanopsin expressing retinal ganglion cells (found in humans in 2001) Vertebrate melanopsin gene – Opn4m
  25. 25. 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
  26. 26. 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
  27. 27. • 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
  28. 28. 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
  29. 29. Thank You!
  30. 30. This concludes The American Institute of Architects Continuing Education Systems Course