Questions on Screen Replacement, Match Move, Analyze Motion, Coloring the Screen

I apologize in advance because I have several questions concerning screen replacement in "Motion 5" (like replacing what's seen on a computer screen in my video with something of my choosing or inserting a new picture into a picture frame that is shown in a video) but they are fairly basic.

I will just list them here but if you think it would be better for me to post each question separately I will do that and delete this post.

1. Some tutorials videos I have seen on replacing screens make a rather big point of changing the color of the screen (the one you are about to film) to green or sometimes to blue. But why? Isn't that for Chromakeying? Don't I instead want something on screen with tracking markers, particularly in the corners?

2. Speaking of creating things for Motion to track; if I create a large plus sign for instance as a tracking marker, where in the plus sign do I want to place Motion's tracking/anchor point? Right where the two lines intersect or slightly to the diagonal in one of the corners?

3. When you use the Match Move and hit the analyze button and it fails for some reason, exactly how do you manually create new keyframes, fix the ones you have and/or delete the bad keyframes? Are you essentially keyframing the distortion parameters of the new screen?

4. Last night I tried an experiment with a clip of a picture frame where I eventually wanted to replace the image in the frame with one of my own - so very much like a screen replacement. What I did was on a new layer I created a black rectangle (could have been any color) and then I keyframed the distortion parameters of each of the four corners of the rectangle so that it covered the picture to be replaced.

My thought was if I could get this to work then I could simply replace my rectangle with the image I really wanted to use in the frame. But it didn't work. I spent almost an hour meticulously distorting the black square, creating keyframes as I went along. What I ended up with was a shaky black square that seemed to float ABOVE the picture frame, it didn't seem ATTACHED if you get what I mean visually.


5. When do you use "Match Move" versus "Analyze Motion" behaviors? At first I thought the technique for screen replacement was to analyze the motion in the background video first and then to apply that analysis to the new screen image I was substituting in but I have since reviewed several tutorials that only used the Match Move behavior with the four corner pin technique

Okay thanks so much everyone for your patience!!!!

Steve Crow

Wow Robin thanks for the detailed response