The Mask of Shame

When the “Cops” style shows were at their peak of popularity, flipping through the TV channels was like it is with poker tournaments today — you couldn’t get away from ‘em. Quite often a few of the faces involved in whatever scuffle was being shown would be blurred out “to protect the innocent” (or, more likely, to protect the broadcaster from getting their pants sued off for the lack of a signed “talent release”).

Well, thank goodness that fad has mostly died out (although the poker tournaments are still with us like a bad hangover on a red-eye home from Vegas). But there are still situations where editors need to obscure something (or someone) in a shot, and there are a few different ways to do it. How it gets done depends on if your subject is moving.

I’ll start with an example that answers a question posted in a comment here a few weeks ago (BTW, for those of you posting comments, I need to personally approve the comment before it shows up on the blog, and due to the massive volume of “comment spam” I get on a daily basis I’m only able to sort through and find the real, non-spam comments every week or so – that’s why it can take so long to see your comment appear). The writer of said comment had a project where he was shooting a computer screen with a spreadsheet on it and he wanted to blur some “sensitive” parts out. I assume this was shot locked-down with a tripod (if not, it should be) so this would be a non-moving subject. We can take care of this one in Premiere Pro.

I’m going to use a different visual example, a locked-down shot of a car with a licence plate I want to get rid of. You need to start with a clip that’s already cut into a timeline. Locate that clip on your timeline, click to select it, then select Edit>Copy. Move the Current Time Indicator (CTI) to the first frame of your clip, and select the video track above it by clicking on the track’s name (it will turn highlighted indicating that it’s selected). Select Edit>Paste, and you’ll have a duplicate copy of your clip sitting right above the original.


Go to your Effects Panel, and in the Contains field type “Gaussian Blur”. Locate the Gaussian Blur effect, then click & drag it to the duplicate copy of your clip on the timeline. Then, go to the Effect Controls Panel and twirl down the controls for Gaussian Blur. Change the Bluriness value to 30 (or whatever value sufficiently obscures your shot).


Now, it’s time to crop this layer so only the area we want blurred out is blurred out, and the un-blurred original copy of the clip is visible below. Go back to your Effects Panel and type “Crop” in the Contains field. Drag the Crop effect to the duplicate clip in the timeline, and then in the Effect Controls click the name of the Crop effect to select it. This will reveal the direct-manipulation Crop controls in the Program Monitor (it’s the outline around the frame with the boxes at each corner). Drag the corners of the Crop controls to isolate only the area you want blurred out.


And that’s all there is to it, as long as you have a locked-down shot with a non-moving subject. If you are dealing with motion, though, it’s time to go over to After Effects. You can select your clip in the Premiere Pro timeline, select Edit>Copy, then Edit>Paste it right into an After Effects timeline.

Over in After Effects, I’m going to use a shot with some actors walking around and blur one of their faces out. The way I’m going to have the blur follow the face as it moves around the frame is by using the Motion Tracker. If you’re using the Standard version of AE then you don’t have the Motion Tracker – so if you need to do this sort of thing you should upgrade to AE Professional.

First, create an Adjustment Layer above the video layer in your AE timeline by selecting Layer>New>Adjustment Layer. Then, go to your Effects & Presets Panel and type “Gaussian Blur” in the Contains field, and drag the Gaussian Blur effect to the Adjustment Layer. Select the Adjustment Layer, go to the Effect Controls, and change Blurriness to 30.

Then, go to the Toolbar and select the Elliptical Mask Tool by holding your mouse button down on the Rectangular Mask Tool and selecting the Elliptical Mask once the pop-up appears.


Make sure your CTI is at the first frame of your timeline, then in the Composition Viewer draw a mask around the face you want to obscure.


To soften the edges of the masked blur, click on the Adjustment Layer in the timeline, hit the letter “F” key on your keyboard to reveal it’s Mask Feather property, then change the Mask Feather value to 8 or so.

Now you’ll need to move the Anchor Point of your layer to the center of your mask (because that’s where we’ll need the motion to be centered). Click on the Adjustment Layer in the timeline once again, then select the Pan Behind tool (it’s the one just to the left of the Elliptical Mask Took). Click-and-drag the Anchor Point of the layer, which by default is dead-center in your Comp, to the center of the mask.


Then, deselect the Pan Behind tool by hitting the letter “V” key on your keyboard.

Okay, now it’s time to motion track our actor’s face, then apply the tracking data to the masked Adjustment Layer so it follows the actor as she moves through the shot. Call up the Motion Tracking workspace by selecting it from the Workspace pulldown menu in the upper-right corner of the interface. Select the video layer in your timeline, then, in the Tracker Controls panel, click the Track Motion button. The Layer panel opens (should be nested with the Composition Viewer) showing the video and a Track Point. Drag the Track Point on to the nose of the actor (or whatever point is appropriate).


It’s worth mentioning here that you’ll have different tracking challenges based on the footage you’re working with, and you’ll want to try and find something to track that has a good amount of contrast. If your track point moves out of view – e.g. the subject turns their head away – you can always track your shot in sections.

Making sure your CTI is at the first frame of the timeline, click the Analyze Forward button in the Tracker Controls – the button that looks like a “Play” button.


The Motion Tracker plays through the shot and tracks your subject. If it isn’t tracking well on your footage, try adjusting the sizes of the inner and outer boxes of the tracker, or clicking on the Options button and checking “Track Fields”. More info on tweaking the AE Motion Tracker for optimal results can be found in AE’s help system by selecting Help>After Effects Help.


Once you have an accurate track, click the Apply button in the Tracker Controls to apply the tracking data to the masked Adjustment Layer (you may need to click the Edit Target button in the Tracker Controls first to make sure that the Adjustment Layer is selected as the target). Click OK in the dialog that appears and your masked blur now follows the motion track.


If you need to get your finished shot back into Premiere Pro, simply use the Dynamic Link feature – drag the Composition from your AE Project Panel and hover it over Premiere Pro on your Windows Taskbar, then drop it into the Premiere Pro Project Panel.

Motion Tracking is a major timesaver for tasks like this (imagine having to manually keyframe that mask over a really long shot) as well as any situation where you want to have an effect or a layer or any other part of your composition follow a moving object within footage. It can also be used to replace entire elements, such as an ad on a moving bus or the contents of a computer screen, by using the Perspective Corner Pin tracker. It’s definitely worth learning how to use, and you’ll be able to say “we’ll fix it in post” with a much higher degree of confidence.

One Response to The Mask of Shame

  1. Julie Hill says:

    Oh my gosh!! I don’t know how I stumbled upon your blog (wasn’t even looking for AE stuff) but I’m so glad I found it! yay! Tons of useful stuff here!