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Filed under: Motion Graphics •Post Production •

Getting Behind the Color Wheel

Ever composite a number of clips, only to have the result like an explosion in a paint factory? This month we’ll search out a variety of plug-in effects for adjusting color and applying tints to video clips. I’m using Adobe After Effects, but many of the same effects are available in other programs. 

Exploring the Color Wheel

Coming from a print background of CMYK color, I was at first bewildered by video’s RGB color space - I even recited the “yellow and blue make green” mantra to no avail. It didn’t take long, however, to discover that the Hue/Saturation/Lightness color picker was far more intuitive, as I could quite easily pick the base color (Hue) and adjust its intensity (Saturation) by moving from the center to the outside of the wheel.

A few traditional acrylic painting classes gave me renewed appreciation for the ease of the digital color wheel, and also uncovered useful color relationship rules. For instance, “Complementary” colors are opposite colors on the color wheel (i.e., blue and orange), “Analogous” colors are adjacent to each other (i.e., a quarter slice of the wheel as in yellow/orange/red); “Triadic” color relationships, as the name implies, are three colors which form an equilateral triangle on the wheel. All in all, adding a little method to the madness of picking colors can’t be a bad thing, and there are lots of good books on color relationships at your local art store.

Leveling the Playing Field

Although the color controls in After Effects are set in RGB color space, it goes without saying that if you’re designing for NTSC video you need to check colors on an NTSC monitor. To ensure that color choices you make stay within NTSC legal colors, you can apply the Broadcast Colors effect to your master comp by nesting it in a new top comp. I dislike the rendering hit and compromises in image quality that this entails, however, and prefer to choose colors more carefully, avoiding totally saturated colors. If I’m unsure, I’ll create a “Test Comp”, nest the master comp and apply Broadcast Colors.  By setting the method to “Key Out Safe”, legal colors are now transparent so I can assume that any remaining pixels are “unsafe”. I then reduce the saturation on the offending layer(s) until the master comp is entirely transparent (safe). I keep the Test Comp around for further checks, but render the master comp as is.

Before you start tweaking colors, you may want to apply the Levels effect to adjust the contrast of the clip. The effect looks a bit unwieldy, but to increase the contrast you only need to use the Input Black, Input White, and Gamma sliders while referring to the useful histogram. (If you’re like me, you’ll rarely use the other 22 sliders.) Alternate plug-ins such as the old KPT Sharpen Intensity Photoshop plug-in (from Kai’s Power Tools v2.1) works well on low contrast video, though you may want to blend it at less than 100%.

If you need to cool off pure white for video output, you can adjust the Levels Output White point to 245 or so, though this will flatten the entire image. To compensate, try adjusting the Input White point by a similar amount so that only the highlights are darkened.

Upper Left: The original four movies in all their colorful glory. Above: A simple 2-color Tint effect applied to each movie, using one base color per movie. For each movie, Black is mapped to a dark tint, while White is mapped to a lighter version, with both tints at 100% saturation. Left: A 3-color Tritone effect using the same tint color per movie. Black is mapped to black, Midtone is mapped to an 85% saturated tint color, and White is mapped to white. The image’s contrast and saturation is easier to maintain using a tritone effect compared to the simpler two-tone Tint.

next page: more creative tinting effects

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