Types of video and film

Some of the source footage you use may have been created digitally (for example, in Photoshop or Adobe Premiere Pro), but other footage may need to be transferred to the computer from analog sources, such as film and videotape. Understanding some of the media differences can help you decide how to handle footage as you transfer it between digital and analog devices.

Analog video

Comes from an analog camera and carries picture and sound information by creating continuous variations in an electromagnetic signal. Before you can import analog video into After Effects, you need to capture it. Capturing transfers video from tape to your hard disk, and involves the conversion of the analog signal to a digital signal.

Digital video

Comes from a digital video camera, and carries picture information by representing each pixel of a video frame as discrete color and intensity values and transmitting and storing the pixel values in the binary data format used by computers. Sound is also carried as binary data.

Digital video is not one format but a category. There are many digital video file formats. Even if your source footage was created digitally, you need to make sure that it is stored in a file format that After Effects can import.

If you plan to distribute the movie digitally, for example on DVD, you must encode the movie into a file format appropriate for your distribution method.

Note: Some formats, such as FLV, have elements of conventional digital video, but represent an intermediate category between what has conventionally been thought of as a video format and what has conventionally been thought of as computer animation format.

Analog film

Carries picture information by creating variations in colored pigments on a strip of acetate (the long reel run through the traditional film projector). Examples include still transparencies and common motion-picture film.

To apply digital effects to motion-picture film using After Effects, you must first transfer the film to a digital format. You can transfer film in two ways:

Use a film scanner to transfer each analog film frame directly to a digital movie frame. This method best preserves the image quality. Using a film scanner is preferable, because you scan the footage directly to the computer as noninterlaced, full-resolution, 24-fps footage; in other words, it is ready to use in After Effects.
Transfer the analog film to analog videotape, and then digitize the videotape. This process is called telecine transfer. It converts 24-fps film footage to 30-fps videotape using 3:2 pulldown. Transferring using the 3:2 pulldown method introduces two issues: You must resolve the different frame rates of videotape and motion-picture film, and you must separate the fields of the interlaced video. After Effects can automatically resolve both of these issues while preserving image quality.

Note: To use an After Effects movie in an analog motion-picture film, you must transfer the movie back to the analog film medium. This transfer process is generally done at a post-production facility.