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What Do You Need to Know About Scanning Modes?

We've discussed scanning, but we haven't looked at how different scanning modes might affect your selection of a DV camcorder. Not every camcorder supports every scanning mode. Depending on the nature of your project, especially its intended release media, you will need to make sure your camcorder supports the needed scanning mode.

Camcorders use two possible scanning modes:

  • Interlaced (mainstay of ATV)
  • Progressive (considered more "filmic")

Interlaced

Interlaced scanning will be with us for awhile, since broadcast technology has to remain backward compatible with the old ATV standard. That means if you're aiming your video project at release on NTSC video, you'll probably shoot in 4:3 aspect ratio, 30I (30 fps, interlaced). Any consumer or professional NTSC DV camcorder will do the job.

Curiously enough, HDTV was originally intended to be compatible with old sets, which meant interlaced scanning. This plan was abandoned as impractical, but one of two predominant HDTV broadcast formats still uses interlaced scanning. It's designated 1080I because it has 1,080 scan lines. So, one scanning mode only available on HD camcorders is 1080I—with a variety of frame-rate options. This HDTV format is designated by the number of scan lines rather than by fps, which can vary by broadcaster.

Progressive

If you are planning to release your project on film, or want your video to look like film, you will probably set your camcorder to use progressive scanning mode, in which interlacing is turned off and the camcorder captures the entire picture one frame at a time, like a motion picture camera. Progressive scanning eliminates artifacts due to interlacing and blurs rapid motion a bit, which contributes even more to a film look.

The most common progressive scanning option for NTSC camcorders is 30P—30 fps without interlacing. Even if you are producing primarily for video, this mode can give a filmed look to your production. A show shot in 30P and converted to NTSC in post will look more like a film that was converted to television.

Another option, which first appeared in HD and is now appearing in prosumer DV camcorders (starting with the Panasonic AG-DVX100), allows you to shoot at 24 instead of 30 fps. This mode is called 24P, which stands for 24 fps progressive. The 24P mode provides a one-to-one match with motion-picture frame rate, and makes for better transfers. Watch for 24P scanning to become an increasingly common DV camcorder feature.

The other most commonly used HDTV mode, found only on HD camcorders, is 720P, which progressively scans 720 lines—at various frame rates (like the interlaced HDTV format, the number of scan lines is fixed but fps can vary by broadcaster).

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