The stroboscopic effect, characterized by a perceptible flickering of LED lights when captured on a camera, has puzzled many photographers and enthusiasts. While these lights appear normal to the naked eye, they often create an unwanted flickering effect when viewed through a camera lens. This phenomenon can be attributed to various factors, including the nature of the power supply, pulse width modulation, and the camera’s frame rate and shutter speed. In this article, we will delve deeper into the stroboscopic effect and explore its causes and potential solutions.
The Persistence of Vision:
To understand the stroboscopic effect, we first need to explore the concept of persistence of vision. Our brains have the ability to retain visual information even after the object being observed is no longer in sight. This allows us to perceive a continuous image rather than a series of discrete static pictures. This principle is also relevant to video playback, where a rapid succession of frames creates the illusion of fluid motion.
Causes of the Stroboscopic Effect:
- DC Power Supply: When an LED light is powered by a direct current (DC) source, such as a battery, the light remains continuously on until the circuit is disconnected. However, when a camera captures an LED light powered by DC, the screen may display a noticeable flickering effect due to the continuous release of light energy.
- AC Power Supply: Alternating current (AC) power from sources like wall sockets cycles on and off. Since the excited electrons in an LED consume energy in the form of light during each cycle, the light appears to flicker when connected directly to AC power. To mitigate this, LED lights are typically connected to a driver that converts AC to DC, resulting in reduced flickering.
- Pulse Width Modulation: Pulse width modulation (PWM) is a technique used to control power consumption by providing discrete pulse currents instead of continuous power. LED lights powered by a driver employing PWM may exhibit flickering. Adjusting the switching period of the driver can help eliminate the stroboscopic effect by surpassing the camera’s frame rate.
Reducing the Stroboscopic Effect:
While completely eliminating the stroboscopic effect is challenging, it can be reduced by adjusting camera parameters, including frame rate and shutter speed. By aligning these settings with the frequency of the power supply, the flickering effect can be minimized.
Additionally, LED lights designed with adjustable flickering frequencies can be controlled by the driver. By setting the flickering rate higher than the camera’s frame rate, it is possible to effectively eliminate the stroboscopic effect.
Comparison with Incandescent Light Bulbs:
Unlike LED lights, incandescent bulbs are powered by AC current. However, their filaments cool down sufficiently during the off state, resulting in a less noticeable effect when captured on a camera. Therefore, incandescent bulbs generally do not exhibit significant flickering when viewed through a mobile phone camera.
Understanding why LED lights flicker on cameras provides valuable insights for photographers and videographers. The stroboscopic effect can be attributed to factors such as the power supply, pulse width modulation, and camera settings. By adjusting frame rates, shutter speeds, and utilizing LED lights with adjustable flickering frequencies, the undesirable flickering effect can be mitigated. As technology advances, further improvements in LED lighting systems will likely reduce the occurrence of the stroboscopic effect, enhancing the visual experience for both photographers and viewers.
