color correction power windows/ mask - key framing/ control in FCP

There are separate keyframe controls for position vs color. You can adjust the color controls of a shape mask, add an "inside mask keyframe" at the current playhead position, move the playhead, and then change the controls. The color mask will change color/brightness at the keyframe positions you add. After adding the first keyframe, subsequent keyframes will automatically be added if you adjust the controls at new playhead positions. Right-click on the timeline clip and select "Show Video Animation" to see the keyframe positions. See attached.

Your description was "move around the frame tracking with a face...physically turn the entire window (color mask) on midway through the shot and back off again before the shot is over (with fade in / out)"

A color mask is frame-wide, so you apparently mean a shape mask added within the color mask effect that constrains it. At a certain point, you want to turn off the color mask, then turn it back on. There isn't a keyframed global disable for that effect, but you can turn the controls to zero at a keyframed point, then at a later point, return the controls to the previous state. That will produce a fade in/out effect as you described.

A color mask added to the color wheels effect will show categories below the wheels: Global, Shadows, Midtones, Highs. Hovering your mouse over each grey horizontal bar will display "show." If you click on that, it reveals a horizontal slider and numeric entry for each parameter.

If you need more vertical space for those controls, if you double-click on the clip name at the top of the pane, it will extend the pane vertically.

I forgot to add, for the case of a combined color and shape mask effect you want to immediately disable, you can set a keyframe, go forward a frame, then turn to zero the "mix" control at the bottom of the pane. That will effectively turn off that effect at the keyframed timeline position. You can then go forward a time period, set a keyframe, go forward a frame, and turn the mix control back to 100%. That will turn the effect back on. So that is a sort of keyframed disable for the combined color and shape mask.

I think I know what he wants. There are cases in a changing scene where a mask needs to "get out of the way." Then you may later want to reactivate the mask using the same color/brightness/balance settings. Expanding the mask or changing the controls is one way -- which is a form of animation.

Another option is leaving the color controls in the same position and keyframing the mix control to alter the intensity of the effect at a user-defined rate. A zero mix setting turns off the effect without changing the other controls, which is why the mix control exists in the Color Wheels effect.

The mix control is independent of the color/brightness/balance settings and also independent of the mask size and position settings. They can each be keyframed separately. So FCP has the features to do exactly what he wants.

I'll start off with — I'm really not sure what you're trying to do here... I haven't really been "getting it" — I may be way off-base here. I'm just putting this "out there" as a possible alternative solution.

It seems (from what you've been describing) that you have a shot where the "corners of the room" are darker than the main subject area.

I don't have an exact similar shot, but I'll use this one:

Center area is lighted and reasonably well exposed. Edge areas are considerably darker... seemingly black.

Apply whatever color adjustments you need to brighten the edges:

apply a shape mask and Invert it so that the color "corrections" are outside the masked area. [The mask is using "inner feathering" — the actual edges of the mask contain the green onscreen control dots and the shape controller (gray dot).]

I didn't have a shot with a person in it, so I made one with this scene and a greenscreen clip and tried to match the brightness (more or less) to the scene:

Then applied the exact same color effects used above using an "adjustment layer" over both the cave shot and the greenscreen to get this:

No mask animations necessary. (I was surprised that the artificially darkened greenscreen clip came out this well with the same base lighting adjustments used originally!)

If you think that animated masks are necessary, an inverted shape mask that covers the entire clip can be animated to a smaller size "inside" the clip to include brightening of faces as needed, then expanded again to get out of the way. The feathering feature can be most useful to keep hard edges around the change of "coloring" or "lighting" from being all that obvious. If there are no "extreme" lighting variations involved, I really can't see where animating masks can be of any use... they'll just make the scene look... weird.

... just my suggestion ... like I said: I'm really not sure what you're going for...

I'd duplicate the clip on top of itself. Delete the color mask from the top copy. Then cut out the parts of the top copy you don't want. Apply cross dissolve transitions.

Luis's solution works, too, but you lose parts of your original.

Depends on what your specific needs are.

For the Color Wheels effect, there is a global control for the shape mask. This allows maintaining the current color/brightness/balance settings and turning it off, then back on with the same settings. It is the "mix" control at the bottom of the pane. The mix control can be keyframed. You can adjust the rate at which the on/off happens based on where you put the keyframes. It can be an instant on/off or a slow fade at a rate you determine.

To set a keyframe for *either* the Color Wheels color/brightness/balance controls *or* the mix control, you press the button at the upper-right of the Color Wheels effect, as shown in the previous image I uploaded. After setting the keyframes, you can view or adjust the keyframe positions by right-clicking the clip in the timeline and picking "Show Video Animation." That shows the current keyframe positions, which you can drag left/right, right-click to delete them, or OPT+click to add one.

Like the color controls themselves, the interpolation rate to a different mix setting happens based on the distance from the previous keyframe. At given color/brightness/balance settings, if you want to go halfway into a clip with mix set to 0 (meaning the effect is off), then rapidly go to 100% (meaning effect is fully on), you must set a starting keyframe at the beginning of the clip, then add one at just before the halfway point. That pins the mix at 0 up to the clip halfway point. Then go a frame after that and change mix to 100%, which automatically adds a keyframe and suddenly turns on the effect at the current color/brightness/balance settings.

If you want a slower transition when enabling the effect, put more space between those two keyframes. You don't need to turn the individual Color Wheel settings up and down to achieve this.

The keyframes for the Color Wheel color/brightness/balance settings are independent from the keyframes for shape mask position. The keyframe button for the shape mask position is at the bottom of the Color Wheels effect pane, beside the shape mask. The keyframe button for the Color Wheel effect is at the upper right of the effect pane.

I am not entirely sure I understood, but it seems to me that all you need is to blade the clip, turn the effect off on one side and on on the other, and add a cross dissolve.