How to Make Light Glow and Bloom in Kdenlive

This article provides a step-by-step guide on how to utilize the “Glow” effect in Kdenlive to create a realistic blooming light source. You will learn how to locate and apply the default Glow effect, adjust its parameters for optimal results, and implement an advanced track-layering technique to achieve a professional, highly-controlled lens bloom.

Method 1: Utilizing the Built-In Glow Effect

The fastest way to add bloom to your footage is by using Kdenlive’s native Glow filter. This filter detects the brightest areas of your clip and applies a soft, radiant blur to them.

  1. Apply the Effect: Open your project, go to the Effects tab, search for Glow, and drag the effect onto your video clip in the timeline.
  2. Adjust the Blur Factor: In the Properties panel, increase the Blur slider. This determines how far the light bleeds outward from the source. A higher value creates a softer, more diffused bloom.
  3. Set the Threshold/Intensity: Adjust the intensity settings to control which parts of the image glow. You want to set this so only the actual light sources (like lamps, sun rays, or neon signs) bloom, while keeping the darker midtones and shadows unaffected.

While the default Glow effect is quick, the best way to achieve a realistic, organic camera bloom is by duplicating your footage and using a blending mode. This method gives you complete control over the shape, color, and intensity of the light bleed without degrading the underlying image.

Step 1: Duplicate and Stack Your Footage

Place your video clip on Track V1. Copy that exact clip and paste it directly above on Track V2, ensuring they are perfectly aligned.

Step 2: Isolate the Light Sources

To make only the lights bloom, you must remove the dark areas from the top clip (V2). 1. Select the top clip (V2). 2. Go to the Effects tab and search for Levels or Lift/Gamma/Gain. 3. Adjust the black point/lift input upward. This crushes the shadows and midtones to pure black, leaving only the brightest light sources visible against a black background.

Step 3: Apply Blur to the Isolated Lights

  1. Search for the Gaussian Blur effect in the Effects panel and apply it to the top clip (V2).
  2. Increase the horizontal and vertical blur values. Because the rest of the clip is black, only the bright light sources will blur and expand outward, creating the bloom shape.

Step 4: Blend the Tracks Together

  1. Right-click the top clip (V2) in the timeline, select Add Composition, and choose Composite and Transform (or simply Screen).
  2. In the composition settings, change the Blend Mode to Screen or Addition.

The black areas of your blurred top track will become transparent, while the softly blurred light sources will seamlessly overlay onto the original video on Track V1. You can now adjust the opacity of the top track to fine-tune the intensity of the bloom.