Douglas- Alpha channels can be used to create a "traveling matte" so you can superimpose ("chroma key" etc.) a moving object onto a static or moving background that is created elsewhere. I use alpha channel in Cool 3D to make 3D animated titles as AVI files with alpha, then I merge that file (superimposing the titles) over my Poser AVI animation. There are many uses for alpha, which work kind of like the transparancy maps in Poser. The alpha channed in Poser generates a black and white layer (or movie in the case of animation) in which all Poser objects are white (or gray if they are transparent) but the background is black. That information can then be used by a video editing program like Premiere to "cut-out" the poser background and merge your Poser foreground animation into another still or motion video.