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Separating fields


    Separating fields is critical if you plan to make significant changes to the footage. When you scale, rotate, or apply effects to interlaced video, unwanted artifacts, such as crossed fields, are often introduced. By separating fields, After Effects accurately converts the two interlaced frames in the video to noninterlaced frames, while preserving the maximum amount of image quality. Using noninterlaced frames allows After Effects to apply edits and effects consistently and at the highest quality.

    After Effects creates field-separated footage from a single formerly interlaced field by splitting fields into two independent frames. Each new frame has only half the information of the original frame, so some frames may appear to have a lower resolution than others when viewed at Draft quality. When you render the final composition, After Effects reproduces high-quality interlaced frames for videotape. When you render a movie at Best quality, After Effects interpolates between the scan lines of a field to produce maximum image quality.

    Note: After Effects automatically separates fields for D1 and DV video footage files. You can manually separate fields for all other types of video footage in the Interpret Footage dialog box. For more information, see Specifying interpretation rules.

To separate video fields in imported footage:

  1. Select the footage item in the Project window.
  2. Choose File > Interpret Footage > Main.
  3. Select an option from the Separate Fields pop-up menu.
  4. Click Motion Detect to increase image quality in nonmoving areas when the image is rendered at Best quality. Then click OK.