Tracking In After Effects

Tracking Tutorial Finished from Becca Nield on Vimeo.

Week 4 Tutorial

The aim of this tutorial was to compose a video in which a green screen is replaced with a background image, which scales in and out and moves when the camera does. The objectives of this were to improve upon skills in tracking and painting on the alpha by hand to make a realistic looking scene.

In order to be able to get a better idea of how use the tracking tool and its many uses some research was required. The tracking tool can be used to stabilise footage as well as making several layers that you have applied move in sync, this is very handy when it comes to scaling green screen footage.

To make this footage the following key steps were used;

·      The Keylight effect was added to the green screen footage, to key in the background image, within key light clip black and clip white were used to get a neater screen matte.

·      Then tracking was used, scale and position were enabled and the two trackers were then placed on the edges of two white crosses (which were but on the green before filming).

·      Then analysing forward frame by frame then commenced, until the trackers lost the edges of the crosses or two other more suitable crosses came in to shot.

·      The background layer and the shot layer was split every time the trackers where changed to a different set of crosses

·      Null layers was created to apply the tracks too, this was then parented to the background layers.

·      Then frame-by-frame the white crosses were painted out on the alpha channel.

·      At the end Levels and Tint were added to the foreground layer to make the colours match the background and Gaussian Blur and Glow were added to make it more atmospheric.

The problems that occurred during the making of this composite were; sometimes the trackers would loose focus too quickly, this was repaired by adjusting the tracker size (making it larger) and by moving it more towards the centre of the cross. When the background was split it moved position this was remedied by manually repositioning it by using the previous background as a template and moving the corner sizing handles of the new layer to match the previous one.

The final outcome of the project was good but could have been improved by having better controlled scaling towards the end as it zooms in and out when the camera doesn’t. The alpha painting could have also been done more accurately especially around the shoulders, as it seems as some parts of the actors shoulder disappears at some points. However the rest of the alpha painting was satisfactory.