Wrote this up as a note on Facebook, posting here in case there's interest.

This is for the FX nerds. Muggles, ye be warned.

I've been playing with emulating two-strip color processing in After Effects. (Two-strip refers to early attempts at color film developed by Technicolor, where two black and white images would be exposed simultaneously in the camera, one through a red filter and one through a green filter. They'd be projected back together, and the result was a very vibrant image heavy in cyan and red hues. You can see this effect prominently in the first third of the film "The Aviator.")

It's tricky, because the effect is very specific - naturally the result of actual light blending in a certain way - and getting After Effects to do it right isn't intuitive for the user or for After Effects. Ultimately, though, the trick to getting a good emulation was pretty straightforward. The airplane above was manipulated using the method and the project I'm gonna post here.

You could probably guess that the secret involves simulating the original process - splitting an image into red and green brothers, and then adding them back to each other. Getting the two images that will become red and green to properly represent their respective color channels is the fun part.

Here's what I did, and let me start by explaining the project file.

http://www.downinfront.net/twostrip.aep

http://www.downinfront.net/twostrip.atn
(Similar Photoshop action, for testing with pictures.)

This will open in After Effects CS3 and above, and is a pretty good starting point for anyone wanting to play with the effect. You import footage into the "Import Footage" comp, and check the results in "Assembly." Most of what you'll want to tweak is opacity adjustment layers in that comp. Naturally this isn't likely to be perfect (or global) when you first import your footage, but it should be pretty close. Tweaking per-shot would be ideal.

However, for this clip I did no shot-by-shot tweaking. The global settings saved as default in the project were used on the whole clip as one. The results are pretty good.

Note that this effect is playing with channel values, and fidelity of individual channels is one of the first things to go when footage is compressed. Uncompressed footage off of a good camera is the best way to go here: I did some tests with Flip footage, and while the effect works the same, the footage becomes blotchy-looking.

The method is as follows.

Footage is imported into a comp, and - this is not set up in the project file - that footage should be white balanced appropriately. (And can be tweaked later - small tweaks to the white balance in the imported footage can have massive changes to what gets divvied up into red and cyan in "Assembly.") This composition is duplicated twice, one to be red, one to be cyan. In each comp, a Channel Mixer is applied in monochrome, favoring the red or green channel respectively. The balance is not 100, 0, 0 or 0, 100, 0, it needs to retain contrast and often going all in for red will result in a mostly white image. In each comp, this footage receives its color channel treatment, and also a Colorama effect, ramping from black to red or turquoise depending on the comp. The result will be a fuzzy image that is black in dark spots, and your color in light spots. It will probably look funny.

In a fourth comp, these items are assembled together. Red is screened on top of green, and the raw effect is the result. Adjustment layers to tweak saturation of red and cyan control specifics, and a monochrome adjustment layer is set to Soft Light to restore contrast utilizing the new colors.

There you have it. I'd love if some folks downloaded the AE project and ran some tests with various kinds of footage (or photos!), I used half a dozen different clips myself and tweaked the project so it worked pretty well with all of them, but as you'd expect, one size certainly doesn't fit all when it comes to color correction. Any inventive extensions of my project would be awesome, or different methods of reaching the desired goal: turning something normal into something really, really cool looking.

Look how pretty Chicago is in two-strip! This is using the default settings in my AE project. (The source was a crappy JPEG to begin with, the artifacting is compression, not the effect.)

Same deal, default settings.