Hue Adjust Node

The Hue Adjust node enables you to perform hue-based color adjustments to an image using the HSV and HSL color models. (To adjust RGB color values, use the Color Correct Node .)

Hue Parameter Tab

Color Space

The Color Space menu allows you to choose the colorspace to use for the adjustment:

  • Hue Saturation Value (HSV)
  • Hue Saturation Luminance (HSL)

The most significant difference between the two colorspaces is that, for HSV, maximum saturation values for any hue are on the same plane in the colorspace as maximum brightness (Value) levels; whereas for HSL, maximum saturation values are on the same plane as midrange brightness (Luminance) levels.

Hue

The first parameter, Hue, allows you to rotate the color distribution vectors of the image 360

around the axis of the colorspace by selecting a value in the range of -180 to 180. A parameter value of 0 represents the hue data of the source image.

You can key a numerical value into the data entry field or use the mouse to set the tuner to the desired value.

Tip:
A vectorscope display of the data is available by clicking the Monitor Scope button on the Hue Adjust Monitor Toolbar (for more information, see the section on Using the Utility Monitors in chapter 8, "Monitors and Flipbooks ").
If Monitor Auto Update (in the Options menu) is turned on, changes to the parameter settings will be displayed interactively in the vectorscope as you make them.

Saturation

The second parameter, Saturation, allows you to adjust the chrominance level of the image by keying a numerical value in the range of -1 to 1 into the data entry box or by using the mouse to set the tuner to the desired value.

A value of 0 always represents the input image data; -1 results in complete desaturation of the image (monochrome); and 1 creates maximum saturation of the hues.

On the Monitor Scope, the degree of saturation is represented by the amplitude of the vector signal, with high saturation indicated by vectors near the outer edge of the scope and low saturation near the center.

Value / Luminance

The third parameter is either Value, if HSV is chosen from the Color Space menu, or Luminance, if HSL is chosen. Both Value and Luminance represent the relative intensity, or brightness, of the color data.

Value and Luminance both use the same range of -1 to 1. A value of 0 represents no change to the input image; -1 results in the minimum brightness; and 1, the maximum brightness.

A parameter setting of -1 will always result in a completely black image for both HSV and HSL colorspaces. A setting of 1, however, will result in blown-out colors for HSV, whereas the same brightness setting for HSL will result in a completely white image.

Note:
It is helpful to remember that two different hues with the same numerical brightness setting may not have the same perceived brightness. Also, the eye is more sensitive to changes in brightness at lower levels; for example, the difference in perceived brightness will be as great between numerical values of .10 and .11 as between .50 and .55.

Control Image Parameters

The Control Action and Control Channel menus enable you to specify how an optional control image input will govern the node operation, as explained in "Using Control Images with Filter Nodes ."




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