April 01, 2022 6 min read
Headlamps are a vital component of the front of your motorized vehicle. They provide you with light to help you see in low-light conditions, and they also alert other motorists that you are approaching them.
The most common type of headlamp is the halogen lamp, which uses an incandescent filament that lights up. Increasingly popular is the LED (light emitting diode) as these bulbs are brighter, more durable with a longer lifespan, and give a better quality of light.
But if you have ever taken a closer look at your headlamps, you may be wondering about their other features.
Why do headlamps have a strobe? Keep reading to find out more.
Strobe, in the context of lights, can have several meanings.
It can refer to a device that produces single or frequent light flashes. Interestingly, the word strobe comes from the Ancient Greek word for whirling, referring to the material in the front of the light that moves. It is this material moving in front of the bulb and then away that creates the flashing effect.
Most headlamps do not have a strobe. This is because bright flashing lights would be far too dazzling and distracting to other road users. That said, it sometimes looks like some headlamps are strobing.
So, if you have noticed headlamp strobing, you may be wondering why this happens. You might have noticed that it only tends to happen with a side-mounted camera – designed to make turning a bit safer than you will be able to see more – and LED lights.
The reason for the strobing effect is twofold.
Firstly, the nature of LED lights can occasionally cause a strobe-like visual. This is because LED bulbs work using Pulse Width Modulation that pulses light on and off. This is great for efficiency and keeping the temperature of the bulb low, meaning the bulb and surrounding pieces of kit last a bit longer.
Keep in mind that the Pulse Width Modulation is always too quick for the human eye to detect – you will only ever see a single light with the human eye. So, in order to see a strobing headlamp, you will need to look at it through some sort of camera.
You will usually be able to see strobing through a camera because a camera will capture frames at a slower rate than the PWD works. Sometimes the frame rate of the camera almost lines up with the PWD rate, making the pulsing LED now visible.
If you are a bit muddled, think of a helicopter. Sometimes a helicopter's blades look like they are stationary on film, even when the helicopter is flying. This is because the frame rate matches the speed of blade rotation. This means that the frame always captures the blades in the same position. It is the same principle.
Strobe lighting has a myriad of uses. Given its broad application, you may find that you do end up using strobe lighting at some point!
In photography, it is usually true that the more light you have the better your image. Using strobe lights will let you take a photo in the middle of a burst of very bright light. Using a separate strobe light will also allow you to adjust, meaning you have greater control over your final images.
Strobe lights are fairly frequently used in aircraft and aeronautic industries to help prevent collisions. This is because a flashing light is more eye-catching and by extension more likely to be noticed, than a light that is just on.
Typically you will see strobe lighting on tall buildings that would have otherwise posed a risk to low-flying planes. You will also notice that there are flashing strobe lights on the underside of flying aircraft, again to help make sure that they are always noticeable.
Lighthouses do essentially the same thing as anti-collision aircraft lights do, just for boats and the land. Again, flashing lights are more noticeable than a flat light and are more easily detected from a distance. This is very important for boats that are not as easily maneuverable so need more warning to change course.
Unfortunate enough to come into difficulty while SCUBA diving? You will be using a strobe light to alert any rescue parties to your whereabouts. The same goes for an emergency light that is used when camping, hiking, or skiing.
Emergency services also use strobe lighting. The lights on top of a police car, firetruck, or ambulance do flash with the siren. You may notice that the siren tends to only go during the day – this is because it is brighter and so the strobe lights are less visible. Conversely, at night the siren tends to not blare but the lights do. This is principally because lights attract enough attention that the siren is unnecessary.
On the whole, strobe lights are perfectly safe for the vast majority of the population. That said, there are some rare side effects or considerations that should be taken into account to guarantee safety.
Strobe lights have been known to cause vertigo, more specifically flicker vertigo. This is a condition that can cause nausea, dizziness, disorientation, and some other problems with the eyes. You can get rid of these symptoms by ending exposure with strobe lighting – they are not permanent.
Perhaps the most well-known strobe-light side effect is epilepsy.
Epilepsy is a seizure condition that is brought on by disturbing nerve activity. Photosensitive epilepsy, therefore, is caused by intermittent lights at some frequencies – this can cover strobe lighting.
But don’t forget that photosensitive epilepsy can be triggered by all types of flickering lights. Including a television screen, emergency vehicle lights, and even shimmering or moving water can be enough to cause a seizure.
One other thing to be aware of is that strobe lights can be used in self-defense products in order to disorientate your attacker. This means that, theoretically, any strobe light could disorientate you.
Strobe lighting can flicker or flash too quickly for the brain to fully adjust, meaning that the information from your eyes will not be processed properly. In short, you will not be able to see properly or think clearly. You may also find that particularly bright strobe lights cause a momentary or temporary ‘after image’ imprint. This is usually described as a blotch in your vision. These imprints will also make it difficult to see clearly without posing any long-term damage.
In short, strobe lights are safe for the vast majority of people. Any side effects experienced by someone who does not have epilepsy will be short-lived and go away fairly quickly. However, those with epilepsy need to be more cautious, especially if you have photosensitive epilepsy. In these instances, strobe lighting can cause seizures.
While the end result is the same – flashing or intermittent bursts of light – a flashing light and a strobe light are technically different.
A flashing light intermittently turns on and off. There is a definite pause in the illumination of the bulb. Strobe light bulbs, on the other hand, are usually always on and there is a separate piece of the light that moves in front of and away from the light source. It is the movement of this additional part of the light that makes it look like it is turning on and off.
Think about a police car’s emergency lights as an example. If you look closely at the bulb or the source of the light, you will notice a piece of plastic that is moving around the bulb. Because the bulb will momentarily be covered, and then uncovered again as the plastic revolves, it looks like the light is turning on and off.
Strobe lights are not used in headlamps as they can be very distracting and disorientating – not ideal for safe driving practices!
However, it may sometimes look like car headlamps are strobing when you are looking through a camera or via your own car’s awareness computer systems. This is because the frame rate of the camera cannot match the rate of an LED bulb, found in most modern headlamps.
Strobe lights are perfectly safe, and any side effects are not permanent and are usually quite short-lived. However, if you have epilepsy you will need to exercise caution as you may be photosensitive. This means that exposure to strobe or flashing lights can induce a seizure.