2. Transparency Transparency (alpha, opacity) defines a pixel color’s visibility in a layer Every element imported into AE contains an opacity channel If an element does not have one, it adds a channel with solid (opaque – white) values This channel can be changed for EVERY pixel using the Opacity attribute with all layers: example: Opacity values 0% – 100%

3. Masks Rather than an attribute to control opacity for every pixel, we can select certain regions to reveal When we “carve out” sections of opacity in a layer, we create what we term a “mask” Masks can be created in a variety of ways Ellipse or Rectangle tools Pen Tool allows us to draw around an object to create a closed curve Mask attributes added to layer: Can keyframe mask shape, select mask, Animation->Create Mask keyframe (can also click on stopwatch next to Mask shape) Move to another frame, reshape, automatically saves keyframe

4. Matte Matting We can also use an image (as opposed to selecting regions ourselves) to control areas of opacity Such images are called mattes, grayscale images We can create them using a variety of tools A matte used with a movie is called a tracking matte

5. Matte examples grey scale images that will define transparency

6. In lab We will work with both masks and mattes to see how they are created or utilized in after effects. We will import this image images into after effects and use the pen tool and a grey scale image to define the regions of transparency.