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April 26, 2010#

Wire Removal with After Effects

Wire removal can be useful for a variety of reasons: sometimes it is for aesthetics, such as getting rid of unsightly power lines, but if you work with stunt people, wire removal will become essential. Unfortunately, wires left behind by stunts tend to be more difficult to remove due to all of the action, moving backgrounds, etc. I recently had to remove a wire from what initially seemed to be an easy clip, but it turned out to be a little more complex and none of the “easy plug-in” methods were going to work, so I had to come up with another, more time consuming method.

Here are a couple of still frames from the before and after clips.

before wire removal

before wire removal

After wire removal process

after wire removal

The problems start with the fact that, rather than a lock-off shot, this one was made on a steadicam, so the background is in constant motion. This is an issue because I want to replace the wire with a piece of background from another frame in this clip, but because of the motion in the background, the pieces have to match in color, texture, light and motion or the fix is as apparent as the wire itself. Also the wire is fairly thick and moves vertically through the frame, so filters such as CC Simple Wire Remover, which cover the wire by extrapolating surrounding pixels, were also ineffective.

My solution started with stabilizing the motion so that I could use a later frame from the shot where the stuntman had cleared the background, and I could use that portion as a clean plate. The shot had to be stabilized to make it easier to match the background with the action, ie: if the action is moving slightly to the left and down, but the plate is moving in a different direction, or not at all, it again becomes apparent you are covering something up. Once the entire clip was stabilized I could start working on removing the wire.

In After Effects, I duplicated the clip, placed it below the original and slid the new layer ¬†which I renamed “Background Plate”, forward in time until the stuntman had cleared the frame enough that I could mask in a fairly good size piece of background. I then went back to the original layer and created a mask large enough to completely cover the wire through it’s entire range of motion. I then set the mask to “subtract”. Here is what that looked like:

Image with background plate masked in

Clip with background plate masked in to cover wire

The Background plate has to be large enough that it doesn’t need to be animated. Any motion in the background will be seen and the shot will not work. I ran the clip a few times like this just to double check that the background will work without drawing any attention. It needed to track a little with the original, but some slight moves, just a few pixels, did the trick. Now I was ready to bring the rest of the stuntman back into the picture.

I duplicated the original layer again, this time leaving it on top of the original clip. Because it was duplicated after the mask had been drawn in, there was a duplicate mask as well. I simply changed the mode to “add” and I had a starting point for the mask that would track with the stuntman and bring his shirt and right arm back into the final clip as shown below.

Picture 9

The final comp: wire is gone and stuntman is whole

I roto-scoped the mask to follow the stuntman’s shirt and arm. The entire clip is less than 2 seconds long so that wasn’t a big issue. After RAM previewing the clip a couple times I added a 9 pixel feather to the masks, made some final adjustments to cover minor problems that became apparent during preview and output the finished clip, which appears below.

after video poster

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2 Comments

  1. Hey – Good wire removal breakdown. Is there any possibility you could make the original source clip available? I would love to have a go at it.

  2. Hey Chillipeppa – sorry it took me so long to get to this, but you can get the file here. Enjoy!

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