After Effects

[David Daniel Doherty]

Hi all, I'm undertaking a new project. The idea is to mask out parts scenes, for example the sky, and replace it with something else.

 

In the attached video clip sample, my process is:

 

Apply an Alpha Matt to original footage, manually mask the Alpha Matt, to remove the sky. Then, frame by frame, animate / track the mask, so it stays aligned with the alpha matt / original footage, during the actual camera move.

 

I'm new enough to After Effects, so any tips on how to improve this technique would be great. The most important part of the process is the accuracy of the mask, as the camera moves.

 

My approach feels a little stone age though?

 

 

http://iplayerhd.com/player/video/feff81b8-9bb7-437d-ae81-31ac71132c49/share

 

 

[Ed Johnson]

Easiest way to mask out sky is to shoot on one of those all blue "chromakey sky"days and simply move your keyed add-in video in your video editing program until it fits the original move. Tracking software can help if really complex.

 

Years ago used a program using splines to create articulated mattes. That feature allowed one to replace just about anything in a scene (like logos) or put people into existing scenes. ED.

[Ed Johnson]

As per above/previous, I clipped out a short piece from a work file and compressed it to fast play to illustrate the "Chomsky" trickChromasky3.movas attached. ED.

[David Daniel Doherty]

Hey, thanks for the reply and reference video.

 

It's great that you were able to key that sky out, with that complex tree in front of it.

 

However, this is something I can already do, without difficulty.

 

Your foreground video is a static tripod shot.

 

What I want to know is what's the best way of tracking that complex (or even a non complex) mask, when using a camera move like in my attached video.

 

Another thought is that having to wait on blue sky days is not practical. I'm in Ireland, we get about one blue sky per decade here! Haha