HD Demystified
By: David Wells
We’re in the golden age of high definition (HD) production and broadcast, and producers looking to step into the all-HD world may find themselves with a wide variety of options, and the many formats of HD available, including HDV and DVCPRO HD. We’ve simplified it with Moving Picture’s Demystifying HD.
HD Basics:
Lines of Resolution: Refers to the number of horizontal lines associated with a frame of video, or a television set or playback monitor.
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Standard Definition: Standard definition has a vertical frame size of 720 x 480 lines of resolution (NTSC, North America) or 720 x 576 (PAL, Europe). Can record in both progressive or interlace.
High Definition: Defined by a vertical frame size of either 720 or 1080 lines of resolution. These are the standard sizes of HD, and the full frame size is 1920 x 1080 (horizontal by vertical resolution) or 1280 x 720. 720 is strictly progressive-scan, while 1080 can be both progressive and interlace. 1080p is considered the highest resolution, and is sometimes called “Full HD.” All HD cameras shoot only in widescreen, 16 x 9.
Ultra-HD: Relatively new to the block is Ultra-HD, defined by horizontal resolution, including 2K (2048 x 1152), made popular by such cameras as Vision Research's Phantom HD Camera, Silicon Imaging’s SI-2K and Arri’s D20/D-21, or 4K (4520 x 2540), from RED (RED ONE) and Dalsa (Origin, Evolution). RED has introduced an upcoming 5K camera, Epic, (5120 x 2880, estimated resolution), and a handheld 3K camera, Scarlet (3072 x 2334, estimated resolution).
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| Phantom HD |
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RED One |
Interlace: The lines in a frame of video are scanned by odd numbered lines, then even. This technology goes back over 75 years, and was the easiest way to broadcast video over the air (remember rabbit ears?) to your television. Since the field is effectively split into two, it becomes a “field.” So 30 fps (29.97, to be exact) will be defined as 60i (59.94, to be exact). There are many benefits, but one major shortcoming is loss of vertical resolution due to scanning of lines. You’ll see 60i used to shoot TV news, reality shows, documentaries, corporate video, and more. It’s also easy to convert 60i footage to 24p.
Progressive-Scan: When lines in a frame of video are scanned one at a time, the resulting image is “cleaner” than interlace. You’ll see it indicated by the video’s frames per second (fps), then “p” for progressive. For example, 24p or 30p, 24 progressive frames per second or 30 progressive frames per second. There is a slight jitter, or flicker to the video, whereas 60i (interlace) and 60p are both smooth.
Progressive Frame Rates:
24p: Since film runs at 24 fps (frames per second), companies use technology to allow their cameras, such as the Sony PMW-EX1 or the Panasonic HVX200, to run at the same frame rate as film. 24p is used typically when shooting movies, TV shows, commercials, music videos, and more. Some disadvantages to shooting 24p include the slight jitter, or flicker look, the difficulty in doing slow motion in post-production, and the inability to do fast camera pans or tilts due to major video frame jitter.
30p: Many television networks and stations are now shooting and broadcasting in HD, using 30p. The image is clean and has an almost film-like quality, due to the progressive-scan, while still maintaining North American standards of 30 fps. 30p is used for TV news, sports, documentaries, and more. A disadvantage to shooting in 30p is the difficulty in doing slow motion in post-production, and converting it to 24p.
60p: As of right now, only cameras that shoot in 720p can support 60p, which is popular for broadcasters. It has more of an appearance of interlace video, but doesn’t lose resolution like interlace can. If you use 60p video on a 24p or 30p/60i timeline, the result will be slow motion. Some cameras can handle this in-camera, like the EX1. 60p is used in sports, TV news, documentaries, and more.
HD Formats:
Now that you’re more familiar with HD, let’s talk about all the different “flavors,” or formats of HD. Manufacturers realize that HD’s signal is large, and can take up a lot of space on a hard drive, so they use compression to “squeeze” the image down to a manageable size. There are trade-offs in picture quality when using a lot of compression.
HDV: Found in both professional and consumer cameras, HDV was the first HD format that could give producers and shooters a chance to work with hi def without the high costs. Using minidv tapes, HDV compresses video using MPEG2-TS (transport system), which makes it manageable to edit. Sony, JVC, and Canon have produced many popular cameras, including the popular Sony HVR-Z1u.
XDCAM: Sony’s XDCAM technology is the next generation of their HD format, using compression similar to HDV, but with less compression. It records to Blu-ray discs (Professional Disc media, single-layer, 23 GB capacity); the XDCAM EX (EX1 and EX3) technology records to solid-state SxS (S by S) cards. The newest format is called XDCAM HD422, which features less compression and records to dual-layer Professional Discs, capable of 50 GB of space.
AVC-Intra: Similar to the AVCHD format, this professional HD format from Panasonic records to P2 cards. The format is considered more robust than even DVCPRO HD, and uses less space on the P2 cards. Cameras include the HPX3000 and HPX2000, which also support DVCPRO HD.
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Panasonic HPX-3000: AVC-Intra. |
DVCPRO HD: Panasonic’s very popular HD format, which is found in their professional line of cameras, including the popular HVX200, HDX900, Varicam, and more. The format can record to tape, which can become costly, or to P2 solid-state cards, a more affordable and reusable solid-state card format.
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Panasonic HVX-200:DVCPRO HD (P2). |
Panasonic HDX-900: DVCPRO HD. |
HDCAM: Sony’s HD format was found in the F900, which George Lucas and others used to replace 35mm film stock for their movies. It is considered to be the most standard of formats. It can record to tape (including the less compressed HDCAM SR), or to special drives that allow for complete uncompressed recording. Newer cameras include the F900r, F950, F23 and F35. The Arri D-21 can output to HDCAM SR.
Viper FilmStream: Thomson Grass Valley’s completely tapeless, uncompressed HD format used primarily for production on major movies, TV shows, commercials and more. David Fincher (Zodiac) and Michael Mann (Collateral, Miami Vice) regularly use this camera.
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