we used video cameras to film a person walking towards the camera with their hand held out. we then used a green screen as a backdrop to film a lighter flame. the green screen was used to allow keying of the background (which removes the background colour).
the idea of the end product was to have the person in the footage carrying a flame in their hand.
the first step was to import the footage into after effects. file>import>multiple files.
the walking scene was added to a new composition and then a motion tracker set up. this is achieved by clicking track motion in the motiong tracking panel. a track point appears, which can be moved to the necessary position. the hand was chosen. the point should have a contrast in colour or brightness to the surroundings, therefore a point on the wrist where the colour was dark was used.
when analyse is pressed the program creates a motion path for the footage. the target is then set to the other image layer. this assigns the layer to the path.
the second layer was then added to the composition and keying used to remove the background. using the colour picker the background colour was selected and then the tolerance changed to remove as much as possible. a second method of background removal was chosen over keying however. we decided to use a mask to cover the area which we did not want to see.
a mask is created by using the pen tool to draw around the desired area. when the area is closed by clicking on the start point of the path, the mask is active. the points can be manoeuvred to change the mask coverage.
now when the composition is played the flame follows the footage and sticks to the hand.
the motion tracking works quite well, however there are a few points where the flame jumps from the hand as the hand has not got many standout areas of colour or light/darkness. a good idea would be to have a small dark object in my hand to contrast with the light skin colour.
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