View a RAM preview by pressing 0 on your keypad and you should now see the basis of the effect in action – each move the dancer makes is echoed a fraction of a second later by a bright orange silhouette. We can improve on this basic implementation and give it a bit more impact by playing with the scale and properties of the echo.
Add the transform effect to the duplicated dancer layer that’s acting as the matte for the red solid layer. By default, this effect does nothing, but it offers us several keyframable properties to play with. The option we’re interested in is scale. Use the Pan Behind tool to reposition the Anchor Point to the bottom of the feet, then starting at 100% and around a second into the compositon, add a keyframe for the scale of the clip. Move one second down the timeline and set the scale to 106%.
You’ve now created a smooth animation in which the silhouette grows in size so that it’s a cartoonesque version of the original. You can repeat this entire process for a second and third copy of the original clip, with each one becoming a little bigger until you have a triplet of echoes. Each should be offset in time a little more than the previous one, thereby creating a wonderful multiple echo effect.
Now take it a little further. Using the same technique of alpha matte you can apply different effects to your solid layers to add internal movement to the silhouettes while retaining the overall outside shape of the animated dancer. The most obvious choice is to add a particle effect.
Create a new solid in a contrasting colour. Using the Pen tool drag some basic flower shapes. You don’t need to be accurate or aesthetically perfect here – quick and dirty will work just as well as precise. Pre-compose the layer (Layer > PreCompose) and drag it to the bottom of the stack, then hide by clicking on the layer eyeball.