The new Motion Key filter in Boris Continuum Complete 4 does the job, almost by magic, with surprisingly good results and without the hours of labor. I’m using FCP as the host here, but any of the other supported BCC 4.0 hosts would work also.

Place your clip in the timeline, navigate in the effects panel to Video Filters > BCC 4 Keys Matte > BCC Motion Key. Drag the filter onto the clip in the timeline, then double click the clip into the source (left) viewer. Switch to the Filters tab in the source window.

When you first apply the filter, you’ll see a white oval being drawn on the image. This is the area that selects the object to be removed. The default is a circle.

In this case, I found the better shape was the rectangle, since it caught the shadows and reflections made by the passing car better then the oval shape did. To change the shape, go to the Area Selection pop-up menu in the filter and change it to rectangle. (Note: Spline is for use in AE only.)

With that done, play through the clip to find the best spot to set the initial remove area. In this case, it’s the middle of the clip where the body of the entire car is visible. Click on the Area Position crosshair dot in the filter, go to the canvas and move the area selection to the middle of the car. Adjust the Area Aspect and Area Scale controls in the filter to encompass the car and its shadows on the ground.

If you were to play with the filter right now and change its output mode from Setup Region to Remove Area, you would see nothing happening. In order for the filter to work, the selection area needs to move from one spot to another. To do that, you need to animate the selection area to track the car. Before you turn white with the thought of tracking something by hand, know that the track only needs to be done pretty loosely. With that in mind, click the Make Keyframe button in the effects window so Final Cut Pro can create your first keyframe.

Go to the beginning of the clip, click on the Area Position crosshair button, and move the area selection over to the left in the canvas (right) window. You can basically just do it by eye, which I did; this is actually good enough in this case. To finish the selection process, scrub through the shot until the car, or whatever your object is, is clear of the frame. Since the FCP canvas window was filling the frame, change the view to 25 percent and set the position of the selection area offscreen to where you think the middle should be. I just made a good guesstimate in the example. Scrub through the clip to watch how close you are; you may have to add one more point or two if you see that your box is too far off.

Time for the magic part: Turn the mode in the Motion Key filter from Setup Region to Remove Area, and your object is now gone. That’s it!

Render your clip and play it back. In my example, it was almost perfect. The car was gone, but a little bit of its shadow remained. Care to guess how I got rid of those little shadows that were left? I exported my rendered clip out to an uncompressed QT file, reimported that, and applied the Motion Key filter again to remove the offending little bits. Bear in mind, however, that the Motion Key filter can be pretty render intensive. I opted to do the export/import thing. This saved time, because I wasn’t rendering the same filter several more times during the final cleanup.

So now what? Well, if all you needed to do was remove the car, you would be done. However, I’m sure you’ve realized that you’ve also just created a clean plate. By using the clean plate and the original clip, you can generate a difference matte to separate either the car or the background from each other; you can now process the two images separately, without a minute of roto time involved. For example, you can make the background black and white, or color correct it for a night or sunset look, while leaving the car alone. Applying the motion key filter gives you several new options for doing unexpected and creative things with the image.

Steve Oakley
Editor/Effects Artist/Founder
Practical Illusions

Steve Oakley is the founder of Practical Illusions, an editorial, effects and motion graphics boutique in Wausau, WI. He’s been working in film and television for more than 18 years and has earned numerous honors, including Telly awards and an Emmy nomination. His work has appeared on several national TV shows, commercials, and syndicated programs.

Steve Says Keep In Mind…
Have you ever wanted to eliminate a moving object from a shot? If the object is small, like a plane in the sky of your 1890s period film, you can paint it out. But what if the object is larger, say as big as a car? Now say the car runs through most of the shot, and instead of clear sky, it’s a complex urban background. Your job just got a whole lot harder. Never mind removing the object from within your NLE environment, such as FCP, Premeire Pro or Avid. Normally, you’d have to send that clip to your compositing application and reimport it. Even if you wanted to take the shot into your compositing application, it still would mean a lot of tedious, careful and time-consuming work. The new Motion Key filter in Boris Continuum Complete 4 does the job, almost by magic, with surprisingly good results and without the hours of labor. I’m using FCP as the host here, but any of the other supported BCC 4.0 hosts would work also.

Practical Illusions
www.practicali.com
408 N. Third St
.
Wausau, WI 54403
ph. 715.848.4264
steve@practicali.com

Support Gear:
Apple Final Cut Pro 5 (Boris Continuum Complete 4 also supports
Apple Motion 2.01, Autodesk Combustion 4, Eyeon Fusion 5
and Adobe After Effects 7.)