Here's an FCPX Effect that gives you very significant grading power all within the one effect:
There is a Master section which includes the 3-way type color wheel controls (recently used in the popular Ripple Training 3-way color corrector effect); this section also includes a range of luma and saturation controls as well as a Tint option.
There is a "Power Window" section for grading inside or outside a shape (selectable between rectangle and circle) with controls for the scaling, positioning and feathering of the shape. In addition to more color controls here, there is an option for blur.
The Highlights/Shadows section (adopted from a previous effect of mine) enables separate grading of the highlights and shadows based on a luma-mask, with lots of control for the mask itself. Note this effect is very powerful and can't be achieved within the FCPX COor Board so it's well worth checking out.
The Diffusion section enables some nice diffusion of either the whites or the blacks or both and can add some really nice enhancement to the grade.
Overall, you can get some really polished looking grades from this effect on its own without having to stack up layers of separate effects to achieve the same result.
Hue; Saturation; Brightness; Gamma; Contrast; Contrast Pivot; Contrast Color Clip Values; Shadows, Midtones and Highlights Color Balance (available as color wheel controls); Color Balance Clip Color Values; Tint Color, Tint intensity; Tint On/Off.
Power Window controls:
Window shape selector (Rectangle/Circle); Window Invert; Window Feather; Window Position; Window Scale; Window Rotation; Brightness; Hue; Saturation; Gamme; Blur; Shadows, Midtones and Highlights Color Balance (available as color wheel controls).
Show Mask On/Off; Mask Strength; MAsk Shrink/Expand; Mask Soften; Mask Erode; Mask Blur; Shadows Brightness; Shadows Gamma; Shadows Saturation; Shadows and Midtones Shadows Color Balance (available as color wheel controls); Highlights Brightness; Highlights Gamma; Highlights Saturation; Highlights and Midtones Highlights Color Balance (available as color wheel controls).
Note there is now an improved version of this (available for download in the original post), which has the extra option of onscreen controls for positioning, scaling and rotating the "power window". (Note that the scaling is uniform so if you want to change the aspect ratio of the shape then you need to use the controls in the Inspector.)
I have also improved the order of the operations, as well as the edge feathering on the power window.
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