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Color Correction Enhancement

Color Correction Enhancement

In this color correction tutorial (which is really color enhancement) we offer color correction methods for basic, intermediate and advanced users.

Most videographers use their camcorder's auto white balance or manually set the white balance. So fixing white balance in post is rarely necessary, and, in any case, it is mindlessly easy to do. So why do professional non-linear video editors (NLEs) have so many tonal and color-correction tools?

They're there to enhance the look and feel of your finished product. In this tutorial, we explain several techniques that should improve your results.

Color Correction is a misnomer. Color Enhancement more accurately describes the purpose of the tonal and color-correction tools you find in most non-linear video editors. The thing is, NLE color-enhancement video effects have such a dizzying array of properties that most videographers don't use them. My goal is to simplify the tonal- and color-enhancement process and encourage you to use these tools in every production.

Tonal and Color Enhancement Workflow

Enhancing tonality and color takes up to four steps:

  • Correcting white balance
  • Adjusting tonality - brightness and contrast
  • Improving color - hue and saturation
  • Colorizing - enhancing the look and feel

Most NLEs offer multiple tools to accomplish each of these tasks. Some tasks take nothing more than a couple mouse clicks; others require an advanced degree in particle physics.

I have organized the steps and their respective tools in four categories: easy, intermediate, advanced and colorist (note: "Colorists" used to refer only to artists who created color cartoons from black line art. Later the moniker also applied to technicians who converted black-and-white films into color. Now colorists also include those who give film or video a particular look and feel. For example: Blade Runner's steel-blue film-noir look or The Bridges of Madison County's Kodachrome orange.)

I used Adobe Premiere Pro CS3 for my examples. Most professional NLEs have similar video effects.

Correcting White Balance

Fig. 1 (Click to enlarge)

Easy: A good rule of thumb is to manually set the white balance (more accurately gray balance) on your camcorder each time you shoot under different lighting conditions. Go that one better, and include a gray card or a black/gray/white calibration card in your opening shot (Figure 1). You'll use that card when you set the white balance in post (see the following Intermediate and Advanced steps). You can make your own calibration card using any image editor. The gray area should have equal RGB (red, green, blue) values. 128 - midway between white (0) and black (255) - works well.

Fig. 2 (Click to enlarge)

Intermediate: Use a white balance video effect. Premiere Pro does not have a white balance effect, but you'll find a white balance option in the Fast Color Corrector video effect. Click the eyedropper tool (Figure 2), hold the Ctrl key (to select a 5x5 pixel area instead of a single pixel) and click on a spot in your video that should be white or neutral gray (this is when you can use the gray card). That tells Premiere Pro to shift the overall color to ensure the white or gray area in your video has no color cast, thereby giving the rest of the clip the proper white balance.

Fig. 3 (Click to enlarge)

Advanced: Correct white balance separately for shadows, midtones and highlights. This is when the black/gray/white calibration card comes in handy. In Premiere Pro apply the Three-Way Color Corrector to your clip. It has three white balance tools (Figure 3). Click each eyedropper on the respective area of the calibration card or on areas in the video clip that should be black, gray and white respectively. Each color balance choice affects only those areas of the clip that are shadows, midtones or highlights.

Fig. 4 (Click to enlarge)
Fig. 5 (Click to enlarge)

Colorist: Adjust the relative size of the tonal range regions for each white balance choice. In the Three-Way Color Corrector, select Tonal Range from the Output drop-down list (Figure 3). That displays how Premiere Pro "sees" shadows, midtones and highlights(Figure 4). You can expand or contract those zones by opening the Tonal Range Definition section and adjusting the appropriate thresholds (Figure 5). Then set the respective Black, Gray and White Balances.

Take this one step further and use the Color Balance effect to adjust individual red, green and blue color channels within shadows, midtones and highlights.

Adjusting Tonality - Brightness and Contrast

Easy: Premiere Pro and other NLEs have two automated tonality effects: Auto Contrast and Auto Levels. Auto Contrast adjusts the overall contrast and mixture of colors. Auto Levels automatically corrects the highlights and shadows. Apply one or both to a low-contrast clip and snap it out of its slumber.

Fig. 6 (Click to enlarge)

The drawback is that if there are any zooms, pans, lighting changes or action in a clip, the auto effect values can suddenly shift. Use Temporal Smoothing (Figure 6). to have your NLE look ahead and back in a clip by the set amount (in seconds) to ease the shift between those changes.

To avoid tonality shifts entirely, you can use the Brightness & Contrast effect and set values manually. Usually, reducing brightness slightly and increasing contrast a bit improves the look of a clip.

Fig. 7 (Click to enlarge)

Intermediate: Use the Levels effect to adjust brightness and contrast. Levels(Figure 7). displays a histogram that shows the relative number of shadows, midtones and highlights. The area between the left (shadows) and right (highlights) slider triangles represents the full 256 shades of gray. Flat areas on either end mean the pixel luminance values in the clip do not span the full grayscale range which creates a low contrast look. Fix that by moving those triangles toward the bases of their respective curves, then moving the center (midtones) slider to adjust contrast.

Fig. 8 (Click to enlarge)
Fig. 9 (Click to enlarge)

Advanced: Use the Levels color channels or the Luma Corrector tonal range selectors. Levels lets you adjust tonality for the Red, Green or Blue channels. Access them via the drop-down list at the top of the Levels Settings dialog box (Figure 7). Luma Corrector has individual controls for shadows, midtones and highlights. Select a tonal range from that drop-down list (Figure 8). and then make your adjustments. To learn about the Luma Corrector's Gamma, Pedestal and Gain properties, check your NLE's Help file.

Colorist: Use the Luma Corrector Secondary Color Correction feature. This option, at the bottom of the properties listing, lets you select an area of a clip based on color, then adjust that selection's tonality (Figure 9).

Improving Color - Hue and Saturation

Easy: Increase saturation to make colors more intense and vibrant. Premiere Pro does not have a saturation video effect, but the Fast Color Corrector has a saturation property. The default value is 100, which does not affect colors. A setting of 0 removes all color (creating a grayscale image). I suggest you try 125 to create a richer overall look to your video.

Fig. 10 (Click to enlarge)

Intermediate: Shift the overall hue to set a mood. The Fast Color Corrector has a Hue Balance and Angle color wheel. Rotating the outer ring (Hue Angle) clockwise shifts the overall color toward red. Counterclockwise shifts toward green. Dragging the little circle in the center toward a color (Balance Magnitude and Angle) increases the intensity of the target color. In Figure 1I rotated Hue Angle 15 degrees toward red and dragged the Balance Magnitude circle toward orange.

Fig. 11 (Click to enlarge)

Advanced: Shift hue values within shadows, midtones or highlights. The Three-Way Color Corrector has three color wheels, one each for shadows, midtones and highlights. In Figure 1 I rotated the highlights and midtones outer wheels toward red, dragged the highlights Balance Magnitude toward yellow to enhance the blond hair and dragged the midtones Balance Magnitude toward orange to give the image a warmer feel.

Colorist: Adjust hue values based on a selected color range. Use the Three-Way Color Corrector Secondary Color Correction feature to select an area of the clip within a color range, and then adjust the three color wheels to individually affect only that selection's shadows, midtones and highlights.

Colorizing - Enhancing the Look and Feel

Here are a few specialized video effects that you might want to try out:

  • Tint :uses pixel luminance to create a blend between two colors. You "map" one color to black (no luminance) and another to white (full luminance). Another way to tint is to create a solid-color matte (orange or blue are good choices depending on the mood you want to set), place it on a track above your clip and reduce its opacity.
  • Leave Color :removes all colors (changes them to gray) except a color range you set. This is a cool way to have an object or person in color with everything else set to gray.
  • Change to Color :adjusts the hue and tonality of a color range you select. This is a fun way to have a colored object shift to another color. You can use keyframes to have colors change over time. Premiere Pro also has a Change Color effect that does more or the less the same thing, but it has fewer options than Change to Color.

I suggest you make enhancing tonality and color a regular part of your video production workflow. Doing so will lead to better results and happier clients.

Jeff Sengstack is an Adobe Certified Expert in Premiere Pro and Photoshop, author of three books on Adobe Premiere and a junior college computer science instructor. He recently completed a video tutorial for lynda.com on Premiere Elements 7, the consumer-level video editor from Adobe.

Tags:  June 2009
Jeff
Sengstack
Mon, 06/01/2009 - 12:00am