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We've all seen footage where a boom pole dip into frame, a shadow fall across your subject, or my personal favorite, a shot where you left a tripod in the background,. Though these kinds of problems can quickly be avoided by choosing an alternate take, you may not always have that luxury. Instead, you may have to use object removal techniques such as scaling and cropping, chroma keying, or motion tracking to get rid of unwanted objects in your footage. We'll show you how to accomplish each of these techniques so that your video can look its best.
Alright. Let's say you have a boom operator who's endurance ran out before the end of a shot leaving you with an ugly black microphone in the top of your frame. Well, if you're lucky enough to be in a situation like this, you can get away with simply scaling your image and then using the edges of your frame to naturally crop out the offending object. Here's an example. As you can see, we have a shot of a spokesperson where a boom microphone drops into frame. To get rid of this distraction, we'll first select our clip. Then we'll go to the "Effects Control" window and twirl down the Motion property. Here you'll see parameters for "Position, Scale, and Opacity". Since we want to make our video larger, we'll twirl down the "Scale" property. Next, we'll use the scale slider to make our video large enough to crop out the boom microphone on the edge of the shot. Once we've done that, we can adjust the framing of our video by using the "Position" property until our video looks normal again. When we play back the video, the boom microphone is no longer visible in our frame allowing us to keep the focus on our subject and not the microphone.
When you don't want to lose resolution and depending on the footage you have, you might be able to save time by using a chroma keying plug-in to remove objects from your footage. The caveat is that the offending object has to be a single color with a background that stays static throughout your shot. Let's take a look at what we'll be dealing with. In this shot, while our speaker is talking to the camera, a blue foam ball goes right through our shot. To get rid of the distraction, we'll first need to start up our Adobe After Effects program. Once the program is open, double click the source footage in the "Project Window", and using the "Footage Window", scrub through the footage until you find a clean background image. In this instance we were wise enough to record some footage at the beginning of the take where our speaker was not in frame so we'll park our playhead on the empty frame. You'll notice that the single frame doesn't have nearly enough content to cover our entire composition. So we'll have to turn our video into a freeze frame. To do this, go to "Layer" in our menu bar at the top of the window, choose "Time", and then select "Freeze Frame." This will allow us to treat our video layer as a still or a photograph and stretch it across the entire length of our composition. With our background plate set, we're ready to do some keying. First, we'll want to drag the video of our speaker and place it on the composition timeline. Next we'll want to go to our "Effects and Presets" window and twirl down the "Keying" option. Select "Keylight" and drag it onto the top layer of footage. We're using the Keylight plug-in because it has a lot of image correction options and an advanced algorithm for finding areas that need to be keyed. Next, we'll go to our "Effect Controls" window and twirl down the "Keylight" option. Then we'll choose the eyedropper tool here in order to show Keylight which color we would like to get rid of in our image. In this case, we want to get rid of the blue foam ball so we'll click on the area in our image that best represents the ball's bluish color. Keylight will do most of the work for us but we may still need to clean up the image a little bit. To do so, go back to the Effect Controls window, choose the "View" drop-down menu, and select "Combined Matte." This will allow us to see the areas that will be keyed in black and the areas that will stay in white. Any semi-transparent pixels will be a shade of gray. To make sure our entire ball is black, we'll twirl down the "Screen Matte" option and scrub the slider for both the "Clip Black" and "Clip White" options until our ball looks completely black. We may also want to go to the "Screen Shrink/Grow option and make our keyed area a bit larger in order to cover any motion blur the basketball might have had. A few pixels should be more than enough for this. If you look at our key right now you can see that there are still a few lingering areas of black around the top of our subject's shoulders and head due to the reflection of the sky. We want to make sure these areas don't get keyed out so we'll duplicate our video layer, remove the Keylight plugin from that layer and make a quick "Garbage Matte" around the top half of our speaker's body. As long as we keep this masked layer on top of our key layer and background plate layer, we shouldn't run into any keying problems with our subject's shoulders. Next, we'll want to duplicate our video layer one more time, remove the Keylight plugin, and place the duplicated layer at the bottom of our composition layer stack. This layer will fill in any gaps around our key layer and our mask. Lastly, we'll need to click on our clean plate layer, which should be right beneath our keyed layer, and choose the Inverted Luma Track Matte option. This will cause the clean plate to only show through the areas of our keyed layer that completely black virtually erasing the foam ball from our scene. Then render a quick preview too see the result. Here's a clip showing the original footage and here's a clip showing what it looks like after our correction.
The last option to get rid of unwanted objects in footage is to use a motion tracker and a mask. This option works in nearly the same way as the chroma keying option we just looked at, but goes a little further in that it can account for objects that are not all one color. To do this, we'll first place our clean background plate in our composition in After Effects and then drag and drop our footage on top of the background layer. Next, we'll create a white color matte by going to "Layer" at the top of the program window, then "New" and finally "Solid." In the "Solid Settings" window you'll want to make sure the solid is the same size as your composition by pressing the "Make Comp Size" button and then double click on the "Color box" and select an absolutely white color. Once you've done that, you can press OK. The solid white layer should show up as the top layer in your composition which is where we want it to be. Next, in order to see the video beneath this layer, we'll turn its visibility off by clicking on the "Eyeball icon" next to the layer. From here we'll want to scrub forward in our video until the boom microphone is as far as it will go into the frame. If we don't do this, our mask may not be adequate enough to cover the entire microphone in later frames. We're going to want to cut the microphone out of the frame using the pen tool. So we'll select our white solid layer and click on the "Pen tool" in the "Tools" window Using the pen tool, we'll create a mask around the boom microphone until each point is connected. Now that our mask is drawn, we'll need to track the boom pole in our footage so that our mask can stay attached to it. If we keep the mask layer static, the effect will begin to break down when the frame moves. To do this, we'll go to "Animation" at the top of the program window and choose "Track Motion." From here we can set our tracking points for position, scale, and rotation and then analyze our footage both in front of the point we scrubbed to in our timeline and behind it as well. With that complete, we'll want to apply our tracking data to the white solid layer so that the solid matches the movement of the boom microphone in the frame. To do this we'll go to our "Tracker" window and choose the "Edit Target" button. The "Motion Target" window will pop up where we can select our solid white layer, then hit "Apply." ()We now only have one step left. Move the background plate layer beneath our solid white layer in the composition. Then turn the solid white layers' visibility on by clicking on the "Eyeball icon" to the left. Lastly, click on the "Track Matte" drop down menu on the background plate layer and choose "Luma Matte." This should allow your background plate to show through the area which the boom microphone previously occupied. Here's how our footage looked before, and here's what it looked like after our correction.
Getting rid of objects in footage is no easy task but it can save an entire production if you know how to do it well. With a little practice, the errors in your footage can go from embarrassing to non-existent in no time at all.