Using Color Balance Controls

The color balance controls (which are sometimes referred to as hue wheels) work as virtual trackballs on the screen; however, they consist of three separate controls.

Figure. Color balance control showing the saturation and hue sliders, reset button, and output display.
  • Color Balance wheel: A virtual trackball that lets you adjust the hue (set by the handle's angle about the center) and saturation (set by the handle's distance from the center) of the correction you're using to rebalance the red, green, and blue channels of the image relative to one another. A handle at the center of the crosshairs within the wheel shows the current correction. When the handle is centered, no change is made.
  • Hue slider: This slider lets you change the hue of the adjustment without affecting the saturation.
  • Saturation slider: This slider lets you change the saturation of the adjustment without affecting the hue. Drag up to increase the saturation, and down to decrease it.
  • H, S reset button: Clicking the H, S reset button resets the color balance control for that tonal zone. If you're using a control surface, this corresponds to the color reset control for each zone. (These are usually one of a pair of buttons next to each color balance trackball.)
  • L reset button: Clicking the L reset button resets the contrast slider for that tonal zone. If you're using a control surface, this corresponds to the contrast reset control for each zone. (These are usually one of a pair of buttons next to each color balance trackball.)
  • Output display: The output display underneath each color control shows you the current hue and saturation values of the color balance control and the lightness value of the contrast slider for that zone.

    Note: The color balance controls can be accelerated to 10x their normal speed by pressing the Option key while you drag.

Using Color Balance Controls with a Control Surface

The three color balance controls correspond to the three trackballs, or joyballs, on compatible control surfaces. Whereas you can only adjust one color balance control at a time using the onscreen controls with a mouse, you can adjust all three color balance controls simultaneously using a hardware control surface.

When you’re using a control surface, the Hue Wheel Angle and Joyball Sensitivity parameters in the User Prefs tab of the Setup room let you customize the operation of these controls. For more information on adjusting these parameters, see Control Surface Settings.

Rebalancing a Color Cast

By dragging the handle of a color balance control, you can rebalance the strength of the red, green, and blue channels of an image to manipulate the quality of light in order to either correct such color casts or introduce them for creative purposes. The color balance controls always adjust all three color channels simultaneously.

In the following example, the image has a red color cast in the highlights, which can be confirmed by the height of the top of the red channel in the Parade scope.

Figure. Image with color cast and Parade scope analysis compared.

To correct this, you need to simultaneously lower the red channel and raise the blue channel, which you can do by dragging the Highlight color balance control. The easy way to remember how to make a correction of this nature is to drag the color balance control handle toward the secondary of the color that's too strong. In this case, the color cast is a reddish/orange, so dragging the color control in the opposite direction, toward bluish/cyan, rebalances the color channels in the appropriate manner. The Midtone color balance control is used because the majority of the image that's being adjusted lies between 80 and 20 percent.

Figure. Before and after a color balance control adjustment.

If you watch the Parade scope while you make this change, you can see the color channels being rebalanced, while you also observe the correction affecting the image on your broadcast display.

Figure. Image and RGB Parade graph before and after a color balance control adjustment.

There are three color balance controls in the Primary In, Secondaries, and Primary Out rooms. Each one lets you make adjustments to specific tonal regions of the image.

About Shadows, Midtones, and Highlights Adjustments

Like many other color correction environments, Color provides a set of three color balance controls for the specific adjustment of color that falls within each of three overlapping zones of image tonality. These tonal zones are the shadows, midtones, and highlights of the image. If you were to reduce the tonality of an image into these three zones, it might look something like the following illustration.

Figure. Illustration of image and its shadow, midtone, and highlight tonal zones.

Three zone controls allow you to make targeted adjustments to the color that falls within the highlights of an image, without affecting color in the shadows. Similarly, they allow you to make separate adjustments to differently lit portions of the image to either make corrections or achieve stylized looks.

To prevent obvious banding or other artifacts, adjustments to the three tonal zones overlap broadly, with each color balance control's influence over the image diminishing gradually at the edges of each zone. This overlap is shown in the following graph.

Figure. Illustration of tonal zones overlap.

The ways in which these zones overlap are based on the OpenCDL standard, and their behavior is described below.

Important: If you're used to the way the Color Corrector 3-way filter works in Final Cut Pro, you'll want to take some time to get used to the controls of the Primary In room, as they respond somewhat differently. Also, unlike adjustments using the Color Corrector 3-way filter in Final Cut Pro, adjustments made using the color balance control affect the luma of the image, altering its contrast ratio.

Shadows Color Adjustments

The behavior of the Shadow color balance control depends on whether or not the Limit Shadow Adjustments preference is turned on. (For more information, see User Interface Settings.)

  • If Limit Shadow Adjustments is turned off: Color adjustments made using the Shadow control are performed as a simple add operation. (The color that's selected in the Shadow color control is simply added to that of every pixel in the image.) The resulting correction affects the entire image (and can be seen clearly within the gradient at the bottom of the image), producing an effect similar to a tint.
    Figure. Example shadow color adjustment with limit shadow adjustments turned off.
  • If Limit Shadow Adjustments is turned on: A linear falloff is applied to color adjustments made with the Shadow control such that black receives 100 percent of the adjustment and white receives 0 percent of the adjustment. This is the method to use if you want to be able to selectively correct shadows while leaving highlights untouched.
    Figure. Example shadow color adjustment with limit shadow adjustments turned on.

Note: To better illustrate the effect of the Shadow color control, the previous examples were shown with Broadcast Safe turned off so that image values below 0 percent wouldn't be clipped.

Midtones Color Adjustments

Adjustments made with the Midtone color balance control apply the correction using a power operation (the new pixel value = old pixel value ^ adjustment). The result is that midtones adjustments have the greatest effect on color values at 50 percent lightness and fall off as color values near 0 and 100 percent lightness.

Figure. Illustration of midtones range.

This lets you make color adjustments that exclude the shadows and highlights in the image. For example, you could add a bit of blue to the midtones to cool off an actor's skin tone, while leaving your shadows deep and untinted and your highlights clean and pure.

Figure. Before and after midtones adjustment.

Highlights Color Adjustments

Adjustments made using the Highlight color balance control apply a multiply operation to the image—the color that's selected in the Highlight color control is simply multiplied with that of every pixel in the image. By definition, multiply color correction operations fall off in the darker portions of an image and have no effect whatsoever in regions of 0 percent black.

Figure. Illustration of highlights range.

The Highlight color control is extremely useful for correcting color balance problems resulting from the dominant light source that's creating the highlights, without inadvertently tinting the shadows. In the following example, a bit of blue is added to the highlights to neutralize the orange from the tungsten lighting.

Figure. Before and after highlights adjustment.

Color Balance Control Overlap Explained

The broadly overlapping nature of color correction adjustments made with the three color balance controls is necessary to ensure a smooth transition from adjustments made in one tonal zone to another, in order to prevent banding and other artifacts. In general, adjustments made to the color in one tonal zone also affect other tonal zones in the following ways:

  • Adjustments made to the Shadow color controls overlap the midtones and the darker portion of the highlights but exclude areas of the image at the highest percentages.

  • Adjustments made to the midtones affect the broadest area of the image but don't affect the lowest percentages of the shadows or the highest percentages of the highlights.

  • Adjustments made to the highlights affect the midtones as well, but not the lowest percentages of the shadows.

Controlling Color Balance Control Overlap

While the tonal zones that are affected by the three color balance controls are predefined by the mathematical operations they perform, it is possible to exert some control over what areas of an image are being affected by the corrections of a particular color balance control. This is done by applying opposing corrections with other color balance controls.

The following example shows this principal in action. If you adjust the Highlight color balance control to add blue to a linear gradient, you'll see the following preview.

Figure. Highlight color adjustment shown in gradient.

As you can see, this change affects both the whites and midtones. If you want to restrict the correction that's taking place in the midtones, while leaving the correction at the upper portion of the whites, you can take advantage of the technique of using complementary colors to neutralize one another, making a less extreme, opposite adjustment with the Midtone color balance control.

Figure. Opposing highlight and midtones adjustments in the color balance controls.

The result is that the highlights correction that had been affecting the midtones has been neutralized in the lower portion of the midtones.

Figure. Resulting change in adjusted gradient.

Although making opposing adjustments to multiple color balance controls may seem contradictory, it's a powerful technique. With practice, you'll find yourself instinctively making adjustments like this all the time to limit the effect of corrections on neighboring zones of tonality.