Select the layer, then edit>split layer where you want the new effect to be applied. Apply the new effect to the new layer.
Otherwise you’ll have to keyframe all the effect values to zero when you don’t want to see the effect … if you just use one layer. Cumbersome and confusing.
Before Graham arrives, allow me to stick my nose in: He might have used a wide angle projector lens with a low throw ratio, which equals projection distance divided by projected width. For example to make a 5 foot wide image from 10 feet away, you need a throw ratio of 2. For a 5 foot wide image from 3 feet away, you need a ratio of .6, if they make such a lens.