Understanding and Eliminating Screen Flicker in Recorded Footage

Have you ever noticed a captivating recording with a TV screen or monitor, only to be dismayed by its flickering and lack of clarity? This issue often arises due to a mismatch in the refresh rate of the monitor and the frame rate of the footage. Let's dive into the details and provide solutions to eliminate this unwanted effect.

What Causes Screen Flicker?

Screen flicker occurs when the refresh rate of the monitor and the frame rate of the footage do not align. The refresh rate of a monitor refers to the number of times the screen is refreshed per second, typically measured in Hertz (Hz). The frame rate of the footage (frames per second, or fps) is the number of still pictures that are played back to create a motion picture.

For the screen to display the recording without flickering, both the refresh rate and the frame rate should be synchronized. This means the refresh rate of the monitor should be a submultiple of the frame rate of the footage. For instance, if the monitor has a refresh rate of 60 Hz, the frame rate of the footage can be 30 fps (a submultiple of 60).

How to Eliminate Flicker

To eliminate flicker, it is essential to ensure that the frame rate and shutter speed of the footage are adjusted to match the screen's refresh rate. This can be achieved by:

Setting the frame rate to a submultiple of the screen's refresh rate. For example, if you are shooting in Europe, where the power frequency is 50 Hz, you can shoot at 25 fps, which is a submultiple of 50. Adjusting the shutter speed to a multiple of the screen's refresh rate. For instance, if you are shooting at 24 fps, you can set the shutter speed to 1/50 or 1/100 of a second.

In regions with a 60 Hz power frequency, the frame rate can be set to 30 fps, and the shutter speed can be adjusted to a multiple of 60, such as 1/60 or 1/120 of a second.

Why It Appears When Watching Footage

Your eyes do not perceive this flicker in real life, but the camera captures images during the flicker, leading to a stroboscopic effect.

Stroboscopic Effect

The stroboscopic effect is a phenomenon where an object is captured in a sequence of non-continuous frames, creating a flickering or paused appearance. This effect can be particularly prominent when shooting at frequencies that are not synchronized with the monitor's refresh rate.

It is essential to understand that different screens have different refresh rates and phases, leading to synchronized flickering. Although it is technically feasible to synchronize screenings for specific purposes (like 'NCIS'), this is usually not necessary for standard viewing conditions.

Practical Advice

To avoid flicker, closely monitor your monitor while shooting. If you notice flickering, adjust your shooting parameters regarding frame rate and/or shutter speed until you achieve a satisfactory result.

By understanding and implementing these principles, you can significantly improve the quality of your recorded footage, ensuring that TV screens and monitors look clear and crisp, free from unwanted flicker.