There are six Hue/Saturation Curves. These are very targeted selections with fine control. Most people use them for secondary color correction. Like the other advanced tools, these can either be seen independently in the full height Inspector, or collapsed into a single panel with buttons and the Mix slider at the bottom.
The first three curves control hue, allowing you to change the hue, and adjust the saturation and luminance of a hue.
HvH, Hue vs. Hue, lets you select a color hue using the eyedropper and change it to a different color.
By dragging a narrow range vertically I can select a different hue in the color wheel to make the sky a rosy pink you might get at dawn. This doesn’t affect anything else in the image which can be controlled with different Hue/Sat Curves.
HvS, Hue vs Sat, is really useful for those annoying colors that need to be toned down. Someone in the background is wearing a bright red shirt, pulling the viewer’s eye from the subject. Select it with the eyedropper and make it a dull red. You can also use it to raise or lower the chroma of a multiple hue ranges, punching up various colors.
HvL, Hue vs Luma, lets you raise or lower the luminance value of a color range without affecting the saturation. This can be useful if specific colors are overly bright and are looking washed out. If you’re working with a narrow band and want to keep the points pinned at a certain level, holding the Shift key will let you drag a point constraining it to move only horizontally.
LvS, Luma vs Sat, lets you pick a luminance value and raise or lower its saturation level. This great for a sky you want to pump up, or weaken something that looks too bright. It’s especially useful for pulling down a color cast in the shadow areas.
SvS, Sat vs Sat, is the tool to push up or lower the saturation of specific levels of saturation. So values that are too high can be pulled down, and unlike HvS, this is regardless of hue. It’s useful when there are multiple elements that are over or under saturated. Pull down the right side, pinning the left to reduce the heaviest saturated areas. Push up the left and pull down the right to balance the saturation across the luminance range.
Finally, there is Orange, Orange vs Sat. The curve isn’t only to control orange, though that can be important as it’s a color that will most commonly cause over-saturation, exceeding broadcast limits. Use the color wheel from the popup on the left or the eyedropper on the right to choose the color whose saturation you want to either raise or lower. Unlike the HvS, the Orange curve lets you lower the saturation in different luminance values of the same color. It’s very useful where you want to to reduce the saturation in the shadows of a selected hue, while raising the saturation in the mids and highlights.
