Three Intriguing Uses of Magnetic Mask in Final Cut Pro

[ UPDATE – July 21, 2025. When I first wrote this article I said that the Magnetic Mask could not be inverted. John Fishback explained how in the comments. So I added one more example at the end of this tutorial to show the process. ]

The Magnetic Mask is a new feature in Apple Final Cut Pro 11 that I really like. It is easy to use, creates amazing masks and opens the door to some fascinating uses.

Mask. A mask selects a portion of the frame. Masks can be a geometric shape, a selected color range, or a selected object. The Magnetic Mask uses machine learning to select a foreground subject.

On a recent trip to China I found a rhinoceros dreaming of distant places. Simply from the look in his myopic eyes, I realized he was desperately pining for a sea-side vacation. Well, who am I to stand in the way of a dream unfulfilled? Since I couldn’t fit him in my suitcase, I did the next best thing.

CHANGE THE BACKGROUND & COLOR CORRECT

To start, put the background clip in the Primary Storyline, then the clip with the image you want to isolate above it. Here’s what the timeline looks like for the effect I’m illustrating.

In Final Cut Pro, put the playhead on the first frame that displays the person/object/rhinoceros you want to select.

NOTE: The Magnetic Mask often creates a glitch on the frame where analysis starts. By placing the playhead on the first frame, it is easy to delete just that errant frame once the finished effect is created.

Then, open the Effects browser (shortcut: Cmd + 5) and navigate to Masks and Keying.

Drag the Magnetic Mask on top of the object you want to isolate in the Viewer (not the timeline). The selected area for the mask turns red.

If you don’t see a red highlight as you drag the Magnetic Mask onto the Viewer, make sure that Final Cut Pro > Settings > General > Drop Effect in Viewer is set to Magnetic Mask.

I missed some of his horn and his front toe, so click the Plus Paintbrush (left red arrow) and select any areas you need to include. If the paintbrush circle is too big, drag the slider (right red arrow) to adjust the size. Then, paint to include the new area.

Hmm… There is an area between the hind legs where the mask is extending to include the background.

Select the Minus Paintbrush. While you could use the slider (cyan arrow) to adjust the circle size, an even faster option is to press the Shift key and drag the mouse until the circle is the size you want. Then, just like painting in Photoshop, drag where you want to remove the selection.

When the selection area (marching ants) is reasonably accurate (you don’t need to be obsessive about this), click Analyze in the top left corner.

This motion tracks the effect throughout the clip, isolating the foreground image.

When analysis is complete, click Done in the top right corner. (Click Reset to erase everything and start over.)

NOTE: You can apply multiple masks to the same image. Select them in the Video Inspector.

Poof! Instant sea-side vacation. Sigh… it’s cloudy. So much for a sun tan.

Except…. the rhino was too bright for this background. So, using the Color Board, I lowered his exposure and modified his position to make his feet look like they were believably placed.

Cool.

PUT TEXT BEHIND AN ELEMENT

For this example, I created a 3D text clip (mostly to show off, you can use any text you like), and placed it above the rhino.

Then, copying the rhino clip, I placed the copy above the text clip.

Here’s what the timeline looks like for this effect – I stacked the exact same video clip on top of itself with the text between them.

Put the playhead on the first frame and select the UPPER clip (Effects are generally applied to the top clip.)

Following the same procedure we covered above, add the Magnetic Mask to the top clip, analyze it, then click Done.

Ta-DAH! Text behind the subject!

NOTE: To make this look a bit better, using the Color Board, I lowered the exposure on the rhino, and reduced feathering a little bit to help the edge of the rhino blend better with the text.

DARKEN THE BACKGROUND

When I first wrote this tutorial, I didn’t know how to invert the mask. So, I wrote this workaround. In the final example, you’ll see how to invert the mask.

Say we want to emphasize the rhino in the frame by lowering the brightness of the area behind the rhino and add some blur to the background.

• Stack a copy of the clip above itself, like we just did in the previous exercise.
• Create the mask in the top clip.
• Then, select the bottom clip in the Primary Storyline, and adjust as desired.

Here, I darkened the background, applied a Focus blur and changed the blur location to emphasize the rhino. Because the rhino is isolated in the foreground and above the lower clip, any changes I make to the lower image will only appear in the background.

NOTE: The glow around the rhino is caused by blurring the background image, which also has the rhino in it.

UPDATE July 21, 2025 – INVERT THE MASK

As John Fishback commented, you can invert the Magnetic Mask, but it CERTAINLY is not obvious and I could not learn how in the Help files.

Similar to what we just did, this two-layer technique separates the foreground from the background so we can process each separately.

Here’s the timeline. The foreground is on top, background on the bottom.

Apply the Magnetic mask to each layer – one at a time – and select the same subject, analyze it, then click Done.

Select the TOP layer, then hover your mouse over the words “Magnetic Mouse” in the Video Inspector. A small rectangular icon appears (upper red arrow). This only appears when you hover the mouse over the title.

Click this icon and a small menu appears (lower red arrow).

Choose Invert Masks. This selects everything outside the mask. For this example, the rhino is isolated in the upper layer clip, while just the background is visible on the lower layer.

Add whatever effects you want. The top image is the original frame. In the bottom image I made the following changes:

Top Layer

• Added the Color Board and lowered highlights

Bottom Layer

• Added the Color Board and lowered highlights and shadows a little and mid-tones a lot
• Added a Blur > Focus effect, and positioned the focal point at the rhino’s feet. This keeps the background in focus with the feet, but creates a distance blur for the rest of the frame.

Notice this using the technique avoids the glow around the rhino’s skin we saw in the earlier example. The Magnetic Mask opens up a wealth of opportunities to apply color grades and effects to moving objects in the frame.

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