Computer Editing: Color Tweaking

When we make video, our goal most of the time is to get lifelike images up on the screen. We chase natural skin tones, good exposure and proper white balance like racing dogs after mechanical bunnies.

But if you watch what’s happening in the movies or on TV, you’re probably already aware that sometimes, realistic just isn’t good enough, particularly when it comes to color.

We accept daytime scenes awash in exaggerated hyper-golden sunlight and nighttime sequences bathed in green or blue. And that’s not all. We even see the use of hybrid scenes, where some of the footage is processed in black and white while other elements retain their colors. The masters seem to come up with new ways to use color every day.

The Countdown of Basics

The first thing to understand about the basics of video color is that at the base level, every television signal is actually a combination of two separate signal components — one for black and white information, the other for color.

In the beginning, all TV signals were exclusively black and white. It wasn’t until years after TV sets started to appear in homes that engineers added a color component to the broadcast signal.

The black and white part of the signal is referred to as luminance and given the engineering shorthand, "Y," while the color signal is known as chrominance and given the designation C.

The standard yellow RCA video plug mixes these signals together into a composite. S-video cables, on the other hand, are sometimes referred to as Y/C cables because they keep the luminance and chrominance signals separated. If you look at the end of an S-video connector, you can see a number of separate holes or pins used to carry the signals.

This split makes it a snap to take a color TV signal from your camcorder and translate it into black and white. Then all that’s left for your software to accomplish is the elimination of the color portion of the video signal.

Diminishing the chrominance signal relative to the luminance yields a reduction of color intensity and creates a muted pastel look. Many editing applications have basic chrominance or saturation controls to adjust this aspect of the video.

But to dive into the more exciting aspects of colorizing your video signal, we also need to break things down further and delve into the three primary components of your signal’s color: red, green and blue.

Engineering RGB Space

Color television is said to reside in the RGB (red, green, blue) color space. It is this arrangement of mixing and matching three basic colors to create the entire pallet of colors the television can display, that makes it a snap to manipulate the color of your video footage.

Most editing software programs allow you to change the balance of the three primary colors on a global, regional or even pixel-by-pixel basis.

Editing applications usually have some basic color manipulation tools, accessible through a panel in the main program or as a plug-in. As you manipulate the colors, you can increase or decrease parameters, such as the amount of red, green or blue applied to your selected part of a picture. You can also alter brightness and contrast, creating a washed-out feel of pastels, or a hyper-real environment, where you deliver suppressed midrange tones and the most extreme dark and light components of your original signals to the screen.

To Boldly Go

Normally, these controls need to be handled with a light touch, since they can dramatically alter the look of your video. Remember, the beauty of working in a non-destructive video-editing environment is that a return to reality is always as close as an "undo" command.

Special-effects filters and plug-ins can often modify colors in interesting ways. Just like the filters photographers have long attached to their lenses to change the image characteristics of their shots, the video filter is simply a way of changing one or more channels of information to create a different look for your video. In most situations, it is better to apply filters in post-production, since you cannot undo on-the-lens glass filters if you don’t like the results.

Many filters have presets for popular color schemes such as sepia – a color effect that alters your footage with a yellowish-brown cast reminiscent of old-time photographs.

Beyond these kinds of simple presets are direct controls such as tint, which you can quickly apply as a global colorcast of your choosing to your footage. All those trendy colorized commercials, where the world is awash in a slightly green tint are examples of manipulating color information. You can simulate these tinting effects with your color control tools.

But a note of caution. Look closely at the colorization examples in broadcast work. You’ll notice that while the environment around that fancy sports car often looks surreal, the people still look pretty realistic. To achieve that kind of sophisticated colorized look, you need to be careful about maintaining healthy skin highlights and other reality checks rather than just slathering everyone and everything with a greenish wash.

That’s where the power of channel-specific effects comes in. Look closely at your editing interface and you may discover that you can apply color corrections to some narrowly-defined parts of your image.

Filters and Mattes

The real fun begins when you combine basic image manipulation with the power of masks, mattes and layers.

If you’ve ever watched a music video, where a brilliantly-colored character danced through an otherwise black and white world, you’ve seen the power of multi-layer mattes and filters at work.

Shots like these stack two or more synchronized layers of the same footage on multiple video tracks. Then, a moving matte applied to the dancing character isolates it from the rest of the scene. The layer with the foreground figure remains in color while a desaturate filter, which removes all of the color information, gets applied to the background footage.

A word of warning: pulling a quality moving matte out of a single video clip without advance planning is just about impossible unless you are willing to go through and paint a matte for every frame of your video (30 of them for every second of footage). But if you have the time and patience (or a team of highly skilled animators), there’s nothing to keep you from going in and isolating a character by re-shaping and moving a manually-created matte to follow the character. When you’re working with it, don’t forget to tweak the softness or blur the edges of the matte to make it appear more natural.

The Adventure Begins

There’s literally no limit to the effects you can create for your videos. To get more ideas on what you can do, the next time you’re watching TV, pay special attention to how the producers use color tinting, layers and mattes to produce eye-catching images. Then, consider that quite possibly, many of those same capabilities reside right in your own system’s editing application – just sitting there, awaiting your exploration.

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