As a motion graphics artist, one of our favorite tricks to enhance an uninspiring clip is not to use effects, but instead to combine it with other clips using Blend Modes (also known as Blending, Composite, or Transfer Modes). Modes provide simple, high-quality ways to drop out the black or white background in a clip, enhance its saturation and contrast, give it a tint, and add lighting effects or a filmic glow in post. I call it our "secret sauce" to create rich, layered imagery you don't normally see created in an editing program.
Happily, Adobe Premiere Pro CS4 added support for Blend Modes, allowing editors to enjoy these sexy results without having to set them up first in After Effects. In this article, I will show you how to apply Blend Modes in Premiere Pro CS5, what sort of results are typical for different groups of modes, and give you some application ideas.
Blend Modes contain different algorithms to combine the pixels of one clip in hopefully interesting ways with the pixels of one or more clips underneath.
The first trick to using Blend Modes in Premiere Pro is finding them, as they're not accessed from the timeline as they are in After Effects or Final Cut Pro.
Select the clip you wish to set the mode for (remember: it must be the one in the upper video track), and open its Effect Controls panel. Click on the arrow to the left of Opacity to twirl open this section, and you will find the Blend Mode popup menu as seen at left. It defaults to Normal, which provides the typical Opacity blend you see during a crossfade.
Underneath the hood, when the Blend Mode is set to Normal the algorithm is "take my pixel color values, multiply them by my Opacity value, and add them to the color values of the corresponding pixels underneath multiplied by the opposite of my Opacity (i.e. 100% minus my opacity value)." Interesting things happen when you use a little more complex math to combine the images.
Below is the clip we wish to enhance. There's certainly nothing wrong with it - it's well-shot and nicely composed - but we can tell an even more interesting story with it if we added some mood lighting or filtering to it:
Clip GU127H1 courtesy of Artbeats.
Next are four different clips we going to explore for providing the desired enhancement. Defocused, slow-moving footage with interesting lighting effects or shadows often provide excellent source material for mode tricks; the first two clips below are examples of these (full disclosure: the second clip is part of a collection I created for Artbeats), and is a concept to keep in the back of your mind when you're out shooting B-roll. The third clip was selected to show off how modes treat blacks and whites. The fourth clip is a blurred version of the original: Applying a treated clip on top of itself using modes can create all sorts of interesting lens and filter effects, with the flexibility of creating them in post rather than in-camera (or on-lens) during the shoot.
In order: clips T307-07H, LAB128H, UM243H, and a copy of GU127H1 (with 60 pixels of blur applied to the original 1080p clip), all courtesy of Artbeats.
Opacity Blend (Normal Mode)
For reference, let's start by looking at the result of the Normal Opacity blend you may be used to. In each of the figures below, the "enhancement" clip was placed above the original clip, and set to 50% Opacity:
Interesting...but note that in most cases, the result lacks contrast and clarity, and is otherwise missing the visual "pop" you might hope for. In the following pages, we'll go in search of that "pop" by setting the enhancement clip's Opacity back to 100%, and trying out different modes.
A Better Luma Key
Many special effects - such as lens flares, stock footage of explosions, and so forth - are shot against a black background. When presented with such a clip, many editors reflexively reach for the Luma Key effect to drop out the black. The result is often an unsightly black fringe around the desired portion of the shot. Fortunately, some Blend Modes provide an alternative to luma keying, often yielding cleaner and more interesting results.
Here are the two shots we wish to composite - a tank, and a fireworks explosion:
To its credit, Premiere Pro's Luma Key effect provides better results than most straight out of the box; its result is shown below at left. A typical result I see out of other programs is shown below at right:
Now let's try the same composite using Blend Modes. Linear Dodge (Add) - shown below at left - essentially adds the pixel values of the clip it is set for to the pixel values of the clip underneath. Since black has a pixel value of zero, these areas of the clip on top add nothing to the corresponding areas of the clip underneath, leaving it unchanged. The result is more akin to adding light to a scene, compared to just layering one clip on top of another. Notice the improved clarity, as well as the more realistic overexposed look of the result. The Blend Mode group that contains Linear Dodge contains other variations on this theme, including Color Dodge (below right):
If there is one thing I hope you take away from this article, it's that you will no longer automatically reach for the Luma Key effect when presented with footage shot against black - you can often get a better result using a Blend Mode.
next page: Overlay, Soft Light, Hard Light, Linear Light, and Vivid Light modes