346 The Digital Filmmaking Handbook, 4E

Color Correction

At its most basic level, color correction consists of adjusting four elements of the image: brightness, contrast, saturation, and hue (see Figure 16.1) While each of these elements can be broken down further and the process can become quite detailed and complex, to give you a basic understanding of color correction, we’ll start with these four components.

Figure 16.1

The four basic elements of color correction: brightness (aka lightness), contrast, saturation, and hue. See also Color Plate 19.

Brightness simply refers to how light or dark the image is (see Figure 16.2). Increasing the brightness in post is similar to increasing the exposure during the shoot: the whole image gets lighter. Typically, you can only adjust the brightness a little bit before the image starts to look noticeably “treated.”

Contrast refers to the range from white to black in the image (see Figure 16.3). A high contrast image has bright whites and blacks that are truly black. Ironically, brightness and contrast filters do not actually control the color in an image but they are key to color correction, and you can fix many basic image quality problems simply by adjusting these two components and nothing more.

Saturation refers to the amount of color in the image. Increasing or decreasing the saturation is a way to refine the look of your color palette (Color plate 19). Hue refers to the overall color cast of your image. Shifting the hue can help correct bad white balance (see Color Plate 20).

Figure 16.2

Adjusting the brightness of an image makes everything in the image lighter (top) or darker (bottom). The blacks go gray in the brighter image and the whites go gray in the darker image.

Just to make things a little more complicated, these four components are related, because different hues have different brightness, so changing the brightness of an image might make colors appear slightly different.

Play with Your Software Filters

We recommend opening your editing application now and using the various color correction filters to adjust the brightness, contrast, saturation, and hue of some of your shots. Be aware that your editing application will probably offer several different ways to adjust color. Play around with them and see what looks better and what looks worse.

Advanced Color Controls

Of the four basic components of color correction, probably the least useful is changing the overall hue because it doesn’t allow for subtle control, and if you have people in your shots, you will be limited as to what you can change if you want to keep skin tones realistic. If your video needs color correction and adjusting the brightness, contrast, and saturation isn’t enough, chances are you’ll need to make adjustments to the individual RGB color channels that make up the hue of your image.

Back in Chapter 3, “Digital Video Primer,” we talked about additive color and how digital video is comprised of three colors of light: red, green, and blue (see Color Plate 1). Added together, they form an image with a complete color spectrum (see Figure 16.4).

Figure 16.4

Each full color frame of video is made up of a red channel, a green channel, and a blue channel.

More sophisticated color-correction tools let you adjust each of these channels separately (see Figure 16.5). The level of control can get quite detailed here. You can adjust brightness, contrast, and saturation within each RGB channel. Some filters let you adjust each of these channels in certain areas of the luminance range: shadows, mid-tones, and highlights. By adjusting the hue in the shadows and highlights, you can avoid shifting the color in skin tones, which usually falls in the mid-tone range.