Flicker Fusion Frequency And Its Impact On Flock Welfare And Performance

I have been reading articles and seeing websites from lighting companies that are rich with speculation, assumption and marketing agenda but absent of facts. So, lets debunk all the fake news and propaganda once and for all.

So yes, to interact with its environment, a chicken needs to perceive objects in both space and time. Temporal resolution as assessed by Flicker Fusion Frequency (FFF) which is the frequency at which a flickering light can no longer be resolved and appears continuous, or Critical Fusion Frequency (CFF) which is the highest flicker fusion frequency at any light intensity.

Look into my eyes Gallus Domisticus

Behavioural experiments using LED-based stimulus show the average CFF in chicken to be 87Hz with a maximum of 100Hz. Please visit this website for a detailed study on the subject: https://www.sciencedirect.com/science/article/pii/S0042698911001519)

Flicker fusion frequency is therefore only important if you are using fluorescent lighting or another lighting technology with a CFF below 100Hz. Fluorescent lights that are dying or been dimmed have a slower flicker rate which is enough to become apparent and annoying. This is also true for poor quality LED products.

Why do LEDs flicker?

LED flicker used to be a common problem. This was because, unlike incandescents, halogens and fluorescents – LEDs have no persistence. When the power supply to an LED is switched off, the light output stops instantly. So, if connected directly to an AC mains-electricity supply, an LED will switch on/off 50 times each second – enough to be visible to the human eye. That’s why some people think LEDs flicker more than older light sources. In the past, that used to be true. But it’s not true today.

LED flicker isn’t a problem for modern LED installation projects. This is because we don’t connect the LEDs directly to the mains supply anymore. Instead, we power our LEDs using an LED driver especially designed for the purpose. LED lighting requires a direct current (DC) rather than an AC power supply. This is good news because the key to eliminating LED flicker is the kind of power-supply you use to drive your lights.

Although the lighting industry generally knows its power supplies (drivers’) simply as ‘LED transformers’, they’re actually more than that. An LED driver doesn’t just step down (transform) voltage. It also converts current from mains AC to DC. Choose a high-quality LED power supply, and it will also supply a constant current to your LEDs. So, you’ll get light with no visible flicker.

A lower-quality, no-frills LED driver doesn’t provide a constant current though. Instead, it simply converts current from AC to DC. This most basic kind of power-supply conversion produces an oscillating current, albeit one that typically doubles the input-voltage frequency. In countries with 50Hz AC supply, that will result in a frequency of 100 potential flickers a second.

Do you see what I see, is it the future?

When it comes to LED lighting, there are two commonly used ways to dim LEDs, either by choking the voltage or by pulse width modulation (PWM).

110/230V AC LEDs with built-in drivers and low voltage luminaires using external, dimmable drivers are dimmed by choking the voltage to the LED chips- less power = less light output. This can allow for a zero flicker which is irrelevant if you are above 100Hz. This form of dimming offers limited range on low dimming contrary to what some spec sheets claim. This makes true Dusk to Dawn functionality impossible. The dimming curve is also non-linear which makes it difficult to programme lights controlled by a PLC.

Dimming LED’s can only effectively be done using PWM (pulse width modulation) technology which is only possible if using an external driver as the dimmer. The PWM frequency [stated in Hz] determines the amount of times the light is being switched on an off within a second. A higher PWM frequency means a higher dimming resolution which leads to incredibly smooth dimming at very low levels. Too high a frequency and it causes electromagnetic interference or EMI. The trick is to hit the sweet spot. The eye of an animal will work out the average between the on and off times and then perceive a certain dim level. Standard lux meters work the same way. The human eye is very insensitive [slow] and can only pick up the flicker at 50Hz and below where a chicken’s sensitivity barrier as described above is 100Hz.

The SUNBIRD Dimmer is set at above 700Hz, so well above the sensitivity level (CFF) of man and bird.

Is it my camera or yours?

While we are on the topic, a camera's video function works in a similar way. A video is a group of pictures shown consecutively at a certain speed called Frame Rate, so while the camera records it is taking multiple photos’ consecutively and grouping them to form a video.

If recording a light and the PWM frequency matches the frame rate of that specific camera then the frequency will not be detected on the screen, if however the frame rate is slower than the PWM frequency then the camera will take pictures of some of the off periods producing the visible disturbance on the screen.

From the farmers mouth

Nobody knows what is better for his birds than the farmer. SUNBIRD lights have been extensively researched and field tested over many years to ensure that our customers get the best possible product available to promote animal welfare and performance and to safe maintenance and operating costs.

Cobb’s Broiler research facility in Brazil has been using SUNBIRD lights as the benchmark for testing various other products and for conducting lighting studies. These lights have been running at this facility since February 2016.

Cobb is using SUNBIRD lighting on its Pedigree Farms with great success and the SUNBIRD product is approved by Cobb’s technical team

“Sunbird lighting has exceeded all expectations, from great technical support to results on the farm.

I highly recommend this great product” Lance Simpson, Pedigree Farm Manager, Cobb- Vantress USA

“Price competitive, long durability, working with the best LED manufacturer in the world and made for our demanding poultry houses” Winfridus Bakker, World Technical Services, Cobb-Vantress

Many Ross and Arbor Acre GP and Breeder farms are running on SUNBIRD lighting with excellent results over many years

“We have installed numerous Sunbird systems in our Hatcheries, Broiler and Breeder operations. All are working perfectly with excellent results and no maintenance required. The service from Sunbird has been exemplary” Raymond Laing, Technical Manager, Ross Breeders Africa (Pty) Ltd


Don’t be fooled by lighting companies using marketing tactics to confuse a simple thing. A chicken cannot see a flicker frequency of greater than 100Hz. Make sure that the LED driver is constant current and constant voltage and, if the system is using PWM dimming, make sure it is over 100Hz.