While a color keyer is the most common method for removing the background of a video, you may occasionally choose to use a blend mode to create a similar effect. This is particularly useful with elements such as highlights, fire, flares, and similar objects. The sample show attached to this recipe shows how a fire is composited onto a background image using an additive blend mode.
Video of a fire, shot against a black background.
The blend mode of the video changed to Lighten.
To try this out for yourself, download the attached “AdditiveBlendModes.zip” file, unzip it, and open it in WATCHOUT. The first video cue runs the video as is, shot against a black background. This is followed by three cues using various additive blend modes. The fire in the example appears to work best with the Lighten blend mode. You may need to experiment to find the blend mode that works best for the images at hand.
To specify the blend mode, double-click the cue, select the Advanced tab, and choose the desired blend mode.
The second example used in this show overlays three images of clouds where the background color has been changed from blue to black in Photoshop. A black background is generally a prerequisite to use an additive blend mode. In this example, the Screen blend mode seems to work best. You can add some transparency to the image as well (using an Opacity tween track), in order to thin out the cloud.