Flicker & Flicker Index Explained

The lighting flicker index (LFI) is a measurement that quantifies the degree of flicker that is present in a lighting system. Flicker is the rapid fluctuation of light output, which can be caused by a variety of factors, such as fluctuations in the power supply or the design of the lighting system.

Flicker can cause a range of negative effects, including eyestrain, headaches, and even seizures in people with certain medical conditions. It can also make objects appear to be in constant motion, which can be distracting or disorienting.

The lighting flicker index is a measure of the percentage of time that the light output is below a certain threshold. The threshold is typically set at 3 Hz or 100 Hz, which are the frequencies at which flicker is most likely to be perceptible to the human eye. The LFI is expressed as a percentage, with a lower percentage indicating less flicker and a higher percentage indicating more flicker.

The lighting flicker index is an important consideration when selecting lighting systems, particularly for applications such as offices, schools, and healthcare facilities where people spend significant amounts of time. Lighting systems with a low LFI are less likely to cause negative effects and are generally considered to be more comfortable and visually appealing.

It is worth noting that the LFI is just one of many factors to consider when selecting lighting systems, and it should be evaluated in conjunction with other factors such as color rendering index (CRI), correlated color temperature (CCT), and energy efficiency.

The acceptable level of flicker in a lighting system depends on the specific application and the preferences of the people using the space. In general, flicker should be kept to a minimum to avoid negative effects such as eyestrain and headaches.

For general lighting applications, the Institute of Electrical and Electronics Engineers (IEEE) recommends that the flicker index should be less than 30%. The IEEE also recommends that the flicker frequency should be less than 100 Hz for general lighting applications.

For applications where people are engaged in tasks that require a high degree of visual precision, such as in laboratories or manufacturing facilities, the acceptable level of flicker is lower. The Illuminating Engineering Society (IES) recommends that the flicker index should be less than 5% for these types of applications.

It is worth noting that some people are more sensitive to flicker than others, and some medical conditions can make people more susceptible to the negative effects of flicker. For example, people with epilepsy may experience seizures when exposed to certain frequencies of flicker.

What is Flicker-free lighting?

"Flicker-free" is a term used to describe lighting systems that produce minimal or no flicker. In general, a lighting system can be considered flicker-free if it has a flicker index of less than 5% and a flicker frequency of less than 100 Hz.

Flicker-free lighting is important because flicker can cause discomfort, eyestrain, and headaches for some people. In addition, flicker can interfere with the operation of electronic devices such as cameras, video cameras, and computer monitors, which can be a concern in some applications.

Many modern LED lighting systems are designed to be flicker-free, and manufacturers may include information on the flicker index and frequency in the product specifications. It is important to select lighting systems that are appropriate for the specific application and to ensure that the lighting system has been tested for flicker to ensure that it meets the desired performance criteria.