5 Keying Tricks in After Effects without Using a Green Screen

If you think of big blockbusters movies, those huge tentpole franchises like the Avengers and others of that fashion, the first thing that comes to mind is that huge studio setup rigged in green fabric with big badass lighting fixtures.

But what can small indie productions do when they need to key something but can’t afford the budget to a complete green screen setup? Green and blue have traditionally been the go-to colors used for keying, mostly for the efficiency they provide when it comes to getting the best results without having spills in the garments and dresses of the talents.

Luckily, there are some cheaper alternative techniques to consider, especially when you are in a pinch. Jordy Vandeput of Cinecom.net has a bag filled with tricks to achieve a similar result even when constricted by a tighter budget, or when simply it becomes impossible to set up a green screen. It could be for lack of space or time, be as it may, let’s take a look.

#1 – Clean Plate

The only requirement for this method is to have the scene filmed with a tripod. Have your talent perform the action and shoot again a clean plate without moving the camera. Then, inside After Effects, pick the “Difference Matte” effect, and apply it to the clip with the subject.

Inside the settings of the effect point the difference layer to the empty shot. As you’ve probably imagined the effect will key out everything that is identical in the two clips, except for your talent. Precompose and add the video over the background you need to. Obviously you cannot expect this technique to be as efficient as a conventional green screen, but in most cases, it will be more than enough to get things done.

#2 – Luma key

The green screen or chroma key is based on selecting a specific hue and eliminating it from the frame. But if instead of removing a selected hue, you can use the luminance information to key out the frame.

Just shoot your subject over an extremely dark (ideally black) background and use the Luma Key. Even the opposite is true, an extremely bright or white background can be keyed out similarly. If refining the edge is not enough to clean up the borders, use the simple choker, that will do the trick.

#3 – Rotoscoping

Rotoscoping is actually a pretty old technique that VFX artists used to do all the time. Ideally, your footage will have a shallow depth of field and there will be a clear separation between foreground and background. Double click on your clip and use the rotoscope brush to draw roughly the shape of your subject.

Holding the Alt key will allow you to refine the selection if you’ve overdone the processing. Press space to play forward and by keeping an eye on the shape, pause to adjust the selection accordingly. When the shape is correct on all frames, you can head out of the Layer and back in your composition where you’ll find that your background is now gone.

#4 – Tracking Matte

The first step is to duplicate your shot. Apply a Curve effect to the top clip, and use it to create a stark contrast. Now, once it’s almost black and white you can use it as a matte for the other shot.

This is actually a very clever trick and an easy one to pull off too. You can just change the Track Matte option on the right column. If you can’t see the latter, you need to enable it first.

#5 – Extract

This key technique is useful if you need to take out a specific tone and luminance value. In the settings, you can adjust the channel you want it to operate on between luminance or a specific hue. You can visually see where the bulk of the information is for each channel and select what you need. The white softness will be useful to clean any color spill.

So those are five simple, yet effective techniques you can use instead of the usual green screen setup. What do you think? Let us know in the comments below.

[source: Cinecom.net]

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