Nesting versus Layering
Previous chapters discussed how to use multiple tracks to create effects like superimposed images, chroma keys, and titles. These effects all use layers to accomplish their design. For example, a resize effect is placed directly on a clip. What if you wanted to change the footage inside the resize effect? Remember, to change something "inside" an effect is to perform a nest. When you work with layers , you're always placing images on top of another. For example, in a picture-in-picture effect, video layer 2 is always on top of video layer 1. This is a classic example of a layered effect and should always be built using this method. But what if you wanted to change the footage inside the picture-in-picture? If you added a new layer to edit the new footage on to or over the picture-in-picture, it would almost be impossible to match any movement, cropping values, or sizing values. Basically, the effect would not look correct. Because you want to change the footage "inside" the picture-in-picture, think about nesting, not layering. There are times when layering effects are your best options and other times when nesting is the best option.
