Flicker is any change in the brightness of the light. It is a loose term that originates from a light defined as a modulation intensity.
Depending on the frequency, people might consider it as a full-on/off solution.
There has lately been a lighting revolution with light-emitting diodes or LEDs replacing incandescent, fluorescent and Compact Fluorescent Lights (CFLs), both indoors and outdoors. LED is an energy-efficient, semiconductor lighting technology. When electricity is passed through it, then the light emits. Nick Holonyak Jr. invented it in 1962. LEDs are energy efficient and have a long life. They are a popular source of light compared to conventional light sources such as incandescent bulbs and CFLs. They are used in home lighting for television, laptop, phone screens, refrigerators, and outdoors in street lights and parking garage lighting. LEDs have several advantages over the conventional lighting system. Much more economical as they use about 25% to 80% less energy; More than 25 times longer lasting than conventional counterparts; Use energy more efficiently and unlike incandescent lamps, which emit 90% of their energy as heat. Cause LEDs emit very less heat; Do not contain mercury, so they are eco-friendly; emit less carbon dioxide. However, a major concern affecting the LED lighting industry is flicker or temporal light modulation. Several investigations reveal that some LED products demonstrate high flicker rate, especially during dimming conditions.
WHAT IS FLICKER? Wilkins AJ et al. in their publication, LED lighting flicker and potential health concerns: IEEE standard PAR1789 update (2010), defined flicker as a rapid and repeated change in the brightness of light over time. The Lighting Handbook (10th ed, 2011), published by the Illuminating Engineering Society of North America (IESNA), defines flicker as a change in the luminous flux of a lamp illuminant in the voltage of the power supply due to fluctuations.
Types of Flicker:
Flicker can be categorized into two types.
Visible: Visible flicker is consciously perceived and is considered unpleasant. It has biological and health effects on humans.
Invisible: Invisible flicker is not consciously perceived; nevertheless, it may still have biological and health effects on humans. Maximum humans are unable to perceive flicker in light above 60-90 Hz. Importantly, flicker is not always harmful. Visible flicker may be used intentionally in discotheques or music concerts for stroboscopic effect (deceptive stopping or slowing motion). Additionally, cyclists and runners use visible flicker as a flashing rear light for safety.
However, in certain environments such as classrooms, offices, hospitals, industrial spaces, and even homes where children/adults are exposed to light for several hours every day, it can cause health issues. Some of the health-related adverse effects of flicker include Headaches, eye strain, blurred vision, and migraines. Aggravation of autism symptoms in children. Photo epilepsy Moreover, children, significantly below three years of age, are more vulnerable to flicker-induced effects than adults. Blue lights are very sensitive for children, and the blue LEDs used in toys produce photochemical damage to the eye. Flicker in specific industrial settings can cause performance issues by causing distraction. It may also lead to accidents because of its stroboscopic effect by changing the perception of rotating or moving machine parts.
How Do Humans Perceive Flicker?
Depending on their sensitivity, humans can detect flicker. The ranges are given below.
- Visible Flicker – Science this will appear as visible flashing or blinking, the naked eye from 3-50 Hz will easily perceive the flicker.
- Critical Flicker Fusion – Humans might Barely perceive it from 50-90 Hz. However, many others will experience an occurrence called critical flicker fusion. The brain will start to see a continuous light source within this range. However, this range can create health hazards.
- Invisible Flicker – Humans might still experience “stroboscopic effects within 90-3000 Hz, that Means the flicker is imperceptible. With a strobe-light type of interference, our interpretation of moving objects, reading, driving, delicate tasks, or sports will be affected.
The effects of flicker depending on the type and magnitude of the hazard. Like most invisible health risks such as toxins, nnEMF, and air pollution, flicker affects everyone differently. A person’s sensitivity to the hazard also affects flickers. Example: asthmatic patients will react differently to a polluted air than an average healthy person. So as like that, a preexisting photosensitive person will respond differently than a healthy person. A healthy person cannot feel the flicker immediately. That is why it is a very subjective topic.
Flicker effect research is not a new thing now. Various health organizations conducted this research, and now it is a well-defined phenomenon.
In the industry, currently, there are no enforced standards on flicker quality, and there are debates on how to address flicker properly.
So, we can already see when it comes to bringing it into the forefront of health topics, but flicker has taken a back-seat:
- It highly depends on the spectator.
- The effects are not always sure about humans.
- Different flicker properties in all lighting sources have other flicker properties.
- For flicker, lighting is not required or enforced standards for flicker in lighting.
- Lack of education on this topic.
The light of hope is that now there is lots of research about flickers. Before knowing the effects of flicker, we should be clear about flicker.
The effect can cause persons who are sensitive to flicker vertigo to experience symptoms like:
- Become disoriented or nauseated
- Rapid blinking
- Behind closed eyelids, experience rapid eye movements
- Control of fine motor functions can be lost.
- Muscle rigidity might be experienced.
These effects are typically not very serious and will most often subside within seconds once exposure.
In extremely rare cases, severe reactions can happen, including:
- Total persistent loss of bodily functions can experience.
- Muscle/motor response loss.
- Aircraft or other moving vehicles’s control loss.
How Does Flicker Affect Us?
The eyes are the primary pathway of flicker. We depend on our eyes for nearly all activities like reading, writing, coordination, work environments, sports, and operating cars and equipment.
In a party or concert to make it cool and pleasant, strobe lights are used. But who are sensitive to the light, they may feel distressed. Your eyes and brain will feel disturbed because of it. A student who is sensitive to flicker light she/he might face problems during reading. Children can more affect things like worsening mood, irritation, etc. It could be a serious cause of neurological damage.
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