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Filed under: Editing •Motion Graphics •

Composite Modes in Final Cut Pro

Multiply

Multiply is sometimes compared to stacking two slides together and projecting the result. With this mode, the color values of the normal clip (V1) are scaled down by the color values of the accent layer on top (V2), resulting in a darkened image that clips at full black. If one of the pixels in the two clips is black, the resulting pixel will be black (since you will be scaling the other pixel by a color value of 0%); if one of the pixels is white, the result will be no change (since you will be scaling the other pixel by a color value of 100%).

Multiply is particularly useful for compositing high-contrast black-and-white clips over background footage: the black areas go to black, and the white areas show the clip underneath - sort of like a track matte. What makes Multiply different from a matte is that the alpha channel is not changed, and the color (not just the luminance) of the clip on top influences the final outcome. A more subtle application is to use the accent clip as a way of adding animated shadows to a normal clip underneath.

Add

With this mode, the color values of the accent clip on top are added to the values of the normal clip underneath, resulting in a brightened, overexposed-looking image, clipping at full white. Each color channel clips individually, often creating color shifts in bright areas as one channel clips while another is still going through its useful range. Note that if a pixel in either clip is black, no change will take place in the corresponding pixel in the other clip (as you would just be adding zero to it); if it is white, the result is white (as you would be adding 100%).

Screen

Screen mode is often compared to the result of projecting two slides from different projectors onto the same screen. It is the opposite of Multiply: The color values of the normal clip are scaled above (not below) their original values based on the color values of the accent clip, resulting in a brightened image that clips at full white. (Technically, the inverse brightness values of one clip are multiplied by the inverse brightness values of the other, then the result is inverted. Sorry - the aspirin’s on me.) If one of the pixels in one of the images is black, no change takes place in the corresponding pixel (the other pixel is not scaled up to be any brighter); if one of the pixels is white, the result is white.

Screen can be thought of as a less intense version of Add, in that Screen does not clip as fast, and it does not approach full white as unevenly. The result can appear washed out, but if you reduce the opacity of the screened layer, it looks more like highlights or adding light to a scene. Depending on your sources, one may be preferable over the other.

A Better “Luma Key”

Many pyrotechnic effects are shot against black, with no alpha channel. Likewise, some plug-ins create synthetic lighting effects against black. Rather than use a Luma Key to separate the pyro or lighting effect from its black background, use the Add or Screen mode to drop out the black and mix the non-black parts of the image.

Top left is the original clip; top right is a pyrotechnic clip shot on black (from Artbeats Reel Explosions 3). Rather than use luma keying to composite these two shots, try Screen (above left) or Add (above right) modes.

However, if the foreground clip is supposed to remain completely opaque (such as a person shot against a black backdrop), Screen or Add won’t work: As you can see from the example above, part of the new background clip will be mixed into the foreground clip. If you need the foreground to be opaque, then you are better off creating a luminance matte or key.

next page: our favorite modes: Overlay, Hard Light, and Soft Light

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