Newbie question here: how do you affect the duration of an emitter--like the StarTrek-like transporter effect emitter, for instance? I know how to place an emitter on a still or moving image, but how does one fadeout an emitter so it doesn't keep looping for the entire clip?
Set a keyframe in the Number graph at the same value as its starting number at the point where you want the emitter to start shutting down, then set another after that with a value of 0. That will shut down the creation of new particles.
You can also add a keyframe to the Active graph, but that will just make all the particles vanish at the chosen frame.