Tutorial: How to Do Motion Tracking with Free Tools

Motion Tracking or Match Moving a shot can be a complex and difficult process... especially when you use expensive tools like After Effects or Motion. Don't get me wrong, those powerful tools can do amazing things incredibly easily if you know how to use them and can shell out the bucks for 'em. But for people like me, who only dabble in special effects shots (sfx) and don't have hundreds of dollars to pour into a hobby, this is the tutorial for you.

In less than 10 minutes, I'll walk you through the steps of creating a motion tracking special effects shot inspired by the fantastic effects in District 9. These aren't anywhere near that, but it's a start. And it's easy. And did I mention, free?

How to do free motion tracking

Media you need: Motion shot (ex. through a window), actor reaction shot, element you will add to the shot.


Step 1: Pull your motion shot into avidemux (sorry, I kept calling it avid-mux, but it's clearly avi demux) and Save Selection as JPEG Images Sequence from File -> Save...

Step 2: Open one of the images in PatchMaker.

Add a New Segment (Segment -> New Segment).

Click on the tiny circle icon on the left of the orange Segment bar and then use the Brush to paint a Mask over an area of the picture that remains in frame. Then press "Enter" to start Processing.

Step 3. Use Gimp to cut out your object and then paste it as a new layer into the first frame of your image sequence. Position as desired, then turn off the image sequence background and save the object as a .png.


Step 4. In PatchMaker, go to File -> Import Overlay... to add your new object.png to the sequence. It should move with the shot now. File -> Render -> Composition... and be sure to add .jpg to the end of the image name.


Step 5. Pull this rendered image sequence into Windows Movie Maker. Select all, and in the Edit tab, adjust the duration to 0.06.

Step 6. Edit as desired with the reaction shot, etc.

That's it. Not too shabby for a first attempt at motion tracking. And wicked easy. And did I mention, free? I first used this technique in a math video back in 2010. I was impressed with how well it worked compared to my painstaking attempt at key framing the motion. It's amazing how much better computers are at tracking motion <smile>.

Enjoy!

 ~Luke Holzmann
Your Media Production Mentor

The Proper Use of Jump Cuts

While in film school, my editing professor told me that my edit was no good because it included a jump cut (a shot so similar to the previous one it looks like the video "jumped"). I explained that there was a very good reason for my decision to include the jump cut. He refused to listen and loudly proclaimed to the entire class, "There is never a good reason to include a jump cut."

He's wrong.

In my case, I cut between two similar shots in a music video because the singer was doing her own vocal backup. Cutting when the second layer of signing came over the first helped accentuate the moment. It was great. It fit and flowed well with the music and camera movement.

Another excellent time to use "jump cuts" is when you need to speed a movement scene up. Say your character is walking into a room. While it's true that you could just cut to the character in the room (and that is absolutely something you should try first), it may be better for your edit to include the entire process of getting in. This is especially true of caper sequences where seeing how the character got into the room is important. But showing the entire process actually detracts from the feeling that your character is deft and in control.

So you cut by jumping through the moments.


Open Door


Walk In

Granted, doing something that looks like the camera glitched is a terrible idea. So it could be argued that the shots above are dissimilar enough so they do not constitute a jump cut. But the question of how different the shots need to be is a very subjective one. And there are many ways to make a jump cut work:

1. Audio Beats Be it music or sound effects, a strong rhythm can drive jump cuts. Nothing proves this better than The Apple Tree Feat. The Glitch Mob. [NB: This video is definitely not suitable for children! It has f-bombs in the lyrics and disturbing/sexually-oriented shots from many R-rated movies.] If you can handle the content, the fast editing is superb and the mash-up excellent.

2. Solid pacing You don't need an audible drive to jump through a sequence (though it sure can help). If you set the pace for a scene with "proper" edits, you can start jumping later as long as the flow continues. Just give your audience a chance to catch your grove, and you're good to go.

3. You want to bother your audience Unexpected jump cuts are incredibly jarring. That is why I'd agree with saying that you should never, ever unintentionally use a jump cut. But you don't have to let your audience know it's coming. If your goal in a scene is to snap them out of your flick for a moment, or get them uneasy in their chairs, dropping one in can be incredibly effective. I can't think of a time I'd want to use this, but that doesn't mean there isn't an excellent reason to pull this tool out of your bag at some key point in the future.

So if you've got a good reason to use a jump cut, do it. My professor gave me some good advice, "Have someone else watch your edit to see if it's any good."

"I did," I replied. "My girlfriend and her family loved it."

"Oh. ...well, get someone who knows how to edit to watch it, not some Joe Blow off the street."

He's wrong again.

"Joe Blow" is exactly who you want to like your edit.

 ~Luke Holzmann
Your Media Production Mentor

Green Screen Tips

Even major productions can't get into locations they want. One solution is to green screen your actors into the scene. Even with really good software and proper setup, the whole scene can feel "off" and fake. Here are a few tips for selling a green screen scene should you find yourself needing to fake it.


1. Establish
Use a solid establishing shot to help the audience know where the actors are supposed to be. This is even more effective if, as in this example, the audience is already familiar with the place.


2. Contextualize
Because green screen scenes are shot in a space that is not the real location, it's easy to forget that the location is supposed to have other people in it. It's a good idea to have a couple extras walk through the frame from time to time to make the scene feel more like it's an actual location than a couple people sitting in front of a painted wall.


3. Make the Best of It
Matching the lighting between your actors and the backdrop is essential. Also, try to remove all the green from the edges, but watch the edge fading as that can look fake too. Ultimately, however, the scene may just look like a green screen, so roll with it. Your story matters more than the effects... unless you're doing an effects movie, in which case, you'd have a production schedule and style that's set up to mask this kind of thing.

One last idea: Match the environment. If it's outside, have fan blow on your actors a bit. If there are things that make sounds--like a fountain--add those bits in post. Selling a green screen shot is all about paying attention to details and working to match them between the foreground and the background.

 ~Luke Holzmann
Your Media Production Mentor