Nuke’s HueCorrect node lets you make precision adjustments to the levels of saturation in a range of hues. You do so via edits to a series of suppression curves.
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| Editing the suppression curve. |
By selecting which curve you edit and how much of that curve you alter, you can precisely limit the influence of the effect.
For the compositor, HueCorrect is obviously of greatest use in diminishing green, blue, or redscreen spill.
| 1. | Click Color > HueCorrect to insert a node at the appropriate place in your script. |
| 2. | Connect a Viewer to the output of the HueCorrect node so you can see the effect of your changes. |
| 3. | In the HueCorrect properties panel, select the channels you want to influence: |
• Click sat to influence all channels (red, green, blue, and alpha) equally.
• Click lum to influence all channels, but with luminance weighting in effect (meaning that the red channel receives approximately 30% of the effect; the green, 60%; and the blue, 10%).
• Click red to apply the curve as a lookup on the red channel only, looking up the pixel's hue on the curve and then multiplying the red value in the pixel by the lookup result.
• Click green to apply the curve as a lookup on the green channel only, looking up the pixel's hue on the curve and then multiplying the green value in the pixel by the lookup result.
• Click blue to apply the curve as a lookup on the blue channel only, looking up the pixel's hue on the curve and then multiplying the blue value in the pixel by the lookup result.
• Click r_sup to apply a suppression function to reduce the level of the red channel. While the red curve is used to directly multiply the red channel by the curve value, the r_sup curve is used to control the amount that the red channel is suppressed.
• Click g_sup to apply a suppression function to reduce the level of the green channel. While the green curve is used to directly multiply the green channel by the curve value, the g_sup curve is used to control the amount that the green channel is suppressed.
• Click b_sup apply a suppression function to reduce the level of the blue channel. While the blue curve is used to directly multiply the blue channel by the curve value, the b_sup curve is used to control the amount that the blue channel is suppressed.
Note that you can select multiple curves in order to edit one curve with reference to another.
| 4. | If necessary, drag the cursor over the Viewer to sample the image pixels that are representative of the part of the image you want to correct. Then, in the HueCorrect properties panel, press Ctrl+Alt (Cmd+Alt on a Mac) while clicking on the curve to plot a particular pixel’s value on the curve. This lets you see what portion of the curve you want to edit. |
| 5. | Edit the curve as necessary - typically this means dragging down on control points in the hue region that you wish to suppress. |
| 6. | To control how much of the original luminance is preserved after the color correction, enable and adjust mix luminance. A value of 0 means the altered luminance is used in the output image. A value of 1 produces a luminance value close to that of the original input image. |
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Original image. |
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| Mix luminance set to 0. | Mix luminance set to 1. |
NOTE: When mix luminance is set to 1, the resulting luminance value is close to the original luminance, but not exactly the same. The difference may vary depending on the color corrections applied to the source image.