Fixing Flickering Lights in 360 Camera Footage

Understanding the Causes of Flickering

Before diving into solutions, it’s essential to understand why flickering occurs. The primary culprit is often the mismatch between the camera’s frame rate and the frequency of the alternating current (AC) power that drives most artificial lights.

• AC Power Frequency: In many countries, AC power operates at 50 Hz or 60 Hz. This means the light source is essentially turning on and off 50 or 60 times per second, although this is usually imperceptible to the human eye.
• Frame Rate Mismatch: When a camera’s frame rate isn’t synchronized with the AC power frequency, it captures these on/off cycles unevenly, resulting in a visible flicker. For example, if your camera records at 30fps and the lights are flickering at 60Hz, you may capture some frames with the light fully on, some with it partially on, and some with it off.
• Electronic Ballasts: Some fluorescent and LED lights use electronic ballasts, which can sometimes produce inconsistent or rapidly fluctuating light output, exacerbating the flickering issue.
• Shutter Speed: A fast shutter speed can worsen the effect because it captures a smaller portion of each AC cycle, making the on/off fluctuations more apparent.

Understanding these causes is crucial for selecting the appropriate strategies to combat flickering.

Prevention Techniques During Filming

The best way to address flickering is to prevent it from happening in the first place. Employing specific filming techniques can significantly reduce or eliminate flickering issues.

Choosing the Right Frame Rate

Selecting a frame rate that’s a multiple or a fraction of the AC power frequency is a key preventative measure. Here’s how to approach it:

• 60 Hz Environments: If you’re filming in a region with 60 Hz power (e.g., North America), use frame rates like 30fps or 60fps. These rates are synchronized with the AC frequency, minimizing flicker.
• 50 Hz Environments: In regions with 50 Hz power (e.g., Europe), use frame rates like 25fps or 50fps.
• Avoid Problematic Frame Rates: Frame rates like 24fps or 48fps can be problematic in either 50Hz or 60Hz environments, as they are not directly synchronized with the AC power frequency.

Adjusting Shutter Speed

Shutter speed plays a significant role in capturing flickering. A slower shutter speed allows the camera to capture more of each AC cycle, averaging out the on/off fluctuations.

• Rule of Thumb: A general guideline is to use a shutter speed that is no faster than 1/ (2 x frame rate). For example, if you’re shooting at 30fps, aim for a shutter speed of 1/60th of a second or slower.
• Experimentation: Experiment with different shutter speeds to find the optimal setting that minimizes flicker without introducing excessive motion blur.

Using DC Lighting

Direct current (DC) lighting, such as battery-powered LED panels, doesn’t have the same flickering issues as AC-powered lights. If possible, use DC lighting sources to eliminate flickering entirely.

Controlling Ambient Light

Sometimes, flickering is more noticeable because of the contrast between artificial and natural light. Try to control the amount of ambient light in your scene to create a more consistent lighting environment.

Testing Before Filming

Always test your camera settings and lighting setup before starting the actual filming. Record a short test clip and review it on a larger screen to check for any signs of flickering. This allows you to make adjustments before committing to a longer shoot.

Post-Processing Techniques for Deflickering

Even with careful planning, flickering can sometimes still appear in your 360 camera footage. Fortunately, several post-processing techniques can help mitigate or eliminate flickering during editing.

Deflickering Plugins

Many video editing software packages offer dedicated deflickering plugins. These plugins analyze the luminance fluctuations in your footage and apply smoothing algorithms to reduce or eliminate the visible flicker.

• ReelSteady GO: While primarily a stabilization tool, ReelSteady GO can also effectively reduce flicker.
• Digital Anarchy Flicker Free: This is a dedicated deflickering plugin that works with various editing software.
• Boris FX Sapphire FlickerRemove: Part of the Sapphire suite, this plugin offers advanced deflickering capabilities.

These plugins often provide adjustable parameters, allowing you to fine-tune the deflickering effect to achieve the best results for your specific footage.

Manual Deflickering Techniques

If you don’t have access to a dedicated deflickering plugin, you can try manual deflickering techniques using your video editing software’s built-in tools.

• Frame-by-Frame Adjustment: This involves manually adjusting the brightness or exposure of individual frames to smooth out the luminance fluctuations. This is a time-consuming process but can be effective for subtle flickering.
• Temporal Smoothing: Applying temporal smoothing can help blend adjacent frames together, reducing the impact of flickering. However, be careful not to overdo it, as this can soften the image and introduce motion blur.
• Luma Keying: Use luma keying to isolate the flickering areas and apply adjustments specifically to those regions.

Using Video Editing Software

Popular video editing software like Adobe Premiere Pro, Final Cut Pro, and DaVinci Resolve offer various tools and effects that can be used for deflickering.

• Adobe Premiere Pro: Utilize the “Reduce Flicker” effect or experiment with adjusting brightness and contrast on a frame-by-frame basis.
• Final Cut Pro: Explore the “Optical Flow” feature for temporal smoothing or use third-party deflickering plugins.
• DaVinci Resolve: Leverage the powerful color grading tools and temporal noise reduction features to minimize flicker.

Workflow Tips for Deflickering

Here are some workflow tips to optimize your deflickering process:

• Apply Deflickering Early: Apply deflickering as one of the first steps in your post-processing workflow. This ensures that the rest of your edits are based on a stable, flicker-free image.
• Render in High Quality: When rendering your final video, use a high-quality codec and bitrate to minimize compression artifacts that can exacerbate flickering.
• Test on Different Devices: After rendering, test your video on different devices and screens to ensure that the deflickering is effective across various viewing conditions.

Advanced Techniques

For particularly stubborn flickering issues, more advanced techniques might be necessary.

Frequency Analysis

Some advanced deflickering tools allow you to analyze the frequency of the flicker and apply targeted filters to remove it. This can be more effective than generic deflickering algorithms.

Motion Estimation

Motion estimation algorithms can track the movement of objects in the scene and compensate for flickering that is synchronized with that movement. This is particularly useful for scenes with a lot of camera or object motion.

Combining Techniques

Often, the best results are achieved by combining multiple deflickering techniques. For example, you might use a deflickering plugin to reduce the overall flicker and then manually adjust individual frames to address any remaining issues.