With all of the techniques and skills that I find interesting and wish to learn I always find the reason for my wanting to learn these techniques is to improve upon my own film/video making. I've been finding a lot of success with compositing as a method to increase the production value of projects that I work. In this post I would like to talk about the "I am Moving" Music video that I worked on for Donny Goines, while I've used compositing many times in the past it is easy for me to illustrate where I used it in "I am Moving."

At its most basics, to composite is to combine multiple images or elements into a single image. This is commonly used in graphic design with applications like photoshop.

We all seem to understand and accept that images are edited and not always what they seem. When it comes to film and/or video there is still an err of magic to the process of combining images and often times, if done correctly, most of us are unaware that any compositing was even done. However, if you look at the credits of even the low budget character dramas being released today you will see a list of Visual Effects(VFX) artists that worked on the project. It would be natural to say "why would that movie need special effects?" What you may not know is that hollywood consistantly uses VFX for things as simple as set extension, or even changing what might be on a television in a shot. In some cases it is even cheaper to shoot in front of a green screen than it is to move an entire film crew to a foreign country.

To illustrate this idea I am going to go over a shot I did for the "I am Moving" music video. To keep this simple I am going to focus on just one shot even though I did compositing on several shots in the video, the shot I am speaking of starts exactly 2:47 into the video(bottom). The crew was in time square New York and it was about 8:30pm. There was a huge crowd of people walking around and we had to fight to find spots to shoot the video. Normally when you shoot in a location like this you would get a permit and hire several of NYC's finest to keep the crowds out and bring extras in. Naturally of course we didn't have that kind of money, infact it was just four of us including the artist with a camera and a tri-pod, gorilla film making at it's finest.

After scouting around looking for a place to shoot we finally came to the end of a V shaped barrier where an opening in the crowd naturally occurred and decided to get a few shots from this position. I looked up and saw all the signage above our heads, that is the hallmark of time-square, and thought we should get some shots with a few signs so I can composite footage onto the large electronic bill boards behind the artist. Naturally we decided to setup the tri-pod and shoot when a police officer came by. "Do you have a permit?" he asked. "No, just shooting some home video" was my reply. Well it turns out you can't use a tripod and shoot in the city without a permit. However, you can shoot hand held without any problems, fire up the boom box.

When I got back to my editing computer I was ready to composite some video and images over those bill boards and make it look like we had total control of the shoot. Since we couldn't shoot with a tripod I knew those bill boards would be moving around as the hand held camera naturally shook a bit. In order for me to composite an image onto the bill boards I knew I would need to track that motion and to do so I used Adobe After Effects. After Effects does a pretty good job of tracking motion in video, what I did was to setup a four corner "perspective" motion tracker and set it to the four corners of the bill board, once I did that I just hit play and let the motion tracker do all the work. Here's how it works, the motion tracker gives you four linked trackers representing the corner of a video element. Each tracker consists of two boxes, the inside box will take a snapshot of the pixels inside of itself, the outside box is the search area. As each frame goes by the snapshot will compare all of the pixels inside the search area and compare them to the last snapshot, when it detects that those pixels have moved it will move the tracker to keep in line with those pixels. Of course it's never that easy, once every second or two there would be a flash coming from the billboard which would throw off my tracker and I would have to manually move the trackers to make sure they stayed inline, of course using the motion tracker is still much easier than editing each frame individually.

Here(right) you can see the motion of the bill board after it has been tracked through around 30 frames, thats about a second of video and you can clearly see how much those trackers have moved. Once I get through tracking the entirety of this shot I can then apply the tracker to an image either still or video, once I do it will force the corners of that image/video to match up with the trackers and it will appear that that video was originally on the billboard, this is simple video compositing.

An additional example of my using motion tracking to composite is a short UFO video I did just for fun a few years ago, I had to track the motion of the clouds in the video in order for the UFO to seem as if it were hover.