Opticals
The optical printer was the first moving image compositing system. By re-photographing processed film in various ways, its operator could produce anything from a simple dissolve to the types of visual effects composites now done almost exclusively with computers.
Computers tend to do things in a rather mathematical and boring way though, unless we tell them otherwise. Opticals allows you to create elegant cross-dissolves, fades to black and “burns” to white with a much more film-like look than one usually gets from a digital video editing system.
In some case you can simply apply Opticals to the video layer in After Effects that contains your source but most often you will find that applying Opticals to its own Solid Layer will give you the most flexibility. To see how this works, read on.
The Opticals controls in After Effects CS3
Opticals is a 16-bits-per-channel effect. You will always get the best results by using Opticals in a 16-bit project, but don't worry if you have to use 8-bit rendering. All the internal calculations are done in higher precision.
When you first apply Opticals, you will need to set the A and B Video Sources using the A Layer and B Layer pop-up menus. The “A” side of a dissolve is the first shot you see, and the “B” side is the second. If you just want to use the fade/burn, you need only choose an A Source—or just choose None (the default), and Opticals will use the layer to which it is applied, after any effect you may have applied above it.
Because Effect plug-ins in After Effects cannot generate video outside the trimmed portion of a Layer in the Timeline, it is handy to apply Opticals to a Solid Layer that occupies the full duration of (and is the same pixel size as) your Composition. In this case you would specify both an A and a B Video Source, which will be other layers in your composition. These layers should be finished, color corrected, and treated with Looks (for Magic Bullet Suite customers). These layers do not need to have their visibility switches enabled in the composition—only the solid does.
The Opticals in After Effects for A/B Roll dissolves
Once you have set up your video sources, you can perform a cross dissolve. To do this, you need only place keyframes for the Dissolve A-B slider. When this slider is at 0%, you are looking at the A Layer only. As you animate the slider up to 100%, you increase the amount of the B Layer that gets mixed in until no more of A is visible.
The Dissolve A-B slider works with the Dissolve Film Response slider. The Dissolve Film Response allows you to change the visual characteristic of the dissolve. If you watch dissolves in films, you may notice that the bright areas of the A side are the last things to fade out over the B side, and the brighter areas of the B side are the first parts to become visible over the A side. This is a general rule in film—light wins out over dark. A great example of this can be seen in John Woo’s 1997 film Face/Off. The first three shots of the films are an A-B-C dissolve (which we’ll show you how to do later!). Watch as the B shot of John Travolta and the young boy (Myles Jeffrey) dissolves to the long shot of the carousel. The white stripes of the carousel are the first parts of C to appear, and the white sky behind the actors in B is the last remnant of B to linger.
Try this with your own footage. With Dissolve Film Response set to 0% you can see what a normal “linear” computer dissolve looks like. Now set it to something like 80%. If your images have pronounced highlight areas you should definitely see a difference in the in-between frames of your dissolve. Setting this value all the way to 100% will produce extreme results, so dial in a value that works for your material.
This is a nice effect and mimics dissolves in modern movies. However, there’s another option here as well. Films shot with color reversal film stock and old three-strip Technicolor films have the opposite thing happening in their dissolves. The dark parts of the image win out and build up before the light parts do, just as if you were holding up two strips of film over each other in front of a light box. Examples of this can be seen all through the 1961 film The Guns of Navarone. To simulate this look (very appropriate if you’re using Looks' 3-Strip Process presets), move the Dissolve Film Response slider below zero into the negative values.
While you’ve got your Guns of Navarone DVD in, roll back to chapter one and take a look at the Columbia logo. As it fades up from black, notice how once again the bright portions of the image pop into view first, with the dark blue field in the background coming slower. The process is repeated when the logo fades out. Opticals replicates this effect with its Fade/Burn slider. At a value of 0% (the default), the result of your dissolve (if any) is shown. Animate Fade/Burn down to -100% though and watch the image perform a nice, smooth fade to black. Dark areas of the frame will fade out more rapidly than bright ones, providing a very cinematic effect. To control this, you have a Fade/Burn Film Response control. At its default value of 90% it produces a nice effect, but feel free to experiment. As with Dissolve Film Response, a value of 0% yields a linear fade similar to what you might get with a video editing application or a simple opacity fade.
You may also wish to perform a “burn to white.” This is easily accomplished by animating Fade/Burn to 100%. The Fade/Burn Film Response control helps you adjust the look of this effect.
To make your life easier, Opticals automatically smoothes out the animation of your dissolves and fades. This allows you to achieve smooth results while only using simple Linear keyframes in the Timeline. If you wish to override this behavior, simply check the Disable Auto Ease checkbox.
What if I just want to use Opticals for simple fades? Great—just apply it to your video layer (or an Adjustment Layer) and leave None as the selection for A Layer. No calculations will be done for the dissolve effect if you leave the Dissolve A-B slider at 0%.
Advanced Opticals
If you want to perform an A-B-C dissolve, you will need two doses of Opticals to do the job. Here’s how you can do this:
As discussed above, selecting None for either A or B layers causes Opticals to use the image it receives from any effects applied above it. This means that if you set up Opticals as described above, then add another Opticals effect below the first, you can set A Layer of the second Opticals to None, and select another Video Layer as the B Layer.
Two instances of Opticals creating and A-B-C dissolve
Now when you dissolve from A to B in the second Opticals, you are dissolving from the results of the first opticals to a third image—something you could even do simultaneously if you wished. In this way you can create very complicated visual collages with a decidedly cinematic feel.