HD camcorders: Buyer's guide - Part Two
Camcorders that house a hard drive tend to be more expensive and bulkier than those that store data on flash media or media cards. The advantage of a camcorder with a 60GB or larger hard drive is that it can record for long periods of time. (You can get camcorders with hard drives that hold as much as 120GB.) For example, if you’re shooting a day’s worth of presentations and don’t want to miss a second to swap in new media, an AVCHD camcorder with a hard drive is a good choice. The disadvantage is that when the drive gets full, and if the camcorder doesn’t offer another storage option (a media card, for instance), you must either delete some of the data on the drive or connect the camcorder to a computer and archive the video, which can take time that you don’t have to spare.
Resolution and frame rate When looking at HD camcorders, you’ll see a variety of numbers followed by an i or a p—1,080i and 720p, for example. These figures indicate the HD video mode: the number of horizontal pixels and the display format. Specifically, 1,080 video offers a resolution of 1,920 (vertical) by 1,080 (horizontal) pixels; 720 video offers 1,280 (vertical) by 720 (horizontal) pixels.
The i and p stand for interlaced and progressive, respectively. Traditional video is made up of odd and even lines (or fields). With interlaced video, each video frame is displayed in alternate fields, horizontal lines that are painted on the screen from top to bottom. So in the case of 1,080i, the 540 odd fields of one-pixel rows are displayed first, followed by the 540 even rows. Progressive video (often called Full High Definition Video by manufacturers) draws every line, from top to bottom, in one pass.
The goal is to produce 30 frames per second (or very close to it). Camcorders that shoot 1080i do this by shooting 59.94 interlaced, odd and even frames per second. This is termed 60i. 1080p camcorders shoot 30 (30p) progressive frames per second.
Some camcorders can optionally shoot 24p video—24 frames of progressive video per second. Because 24 fps is the standard used in motion pictures, shooting at this rate on a camcorder gives the video a more cinematic look. And because the shutter speed is lower (so more light can touch the sensor), 24p also gives you better low-light video. Additionally, video shot at 24p contains fewer frames and therefore consumes less storage space.
Progressive video looks cleaner than interlaced video, particularly when there’s a lot of movement in the image. You’re less likely to notice the difference between interlaced and progressive video on a television because TVs are designed to account for interlaced video—they either support interlacing natively (standard-definition TVs) or include deinterlacing circuitry (HDTVs) that converts interlaced video to progressive video. Computer monitors, which are progressive-scan devices, don’t include deinterlacing, which is why interlaced video can look jagged on them.
For this reason, it’s important to consider where your video will eventually appear. If that’s a TV, either interlaced or progressive video will do. If your video is likelier to appear on computer screens, progressive is the better choice.
Midpriced full-size camcorders typically shoot in 1080i, whereas more-expensive camcorders offer 1080p video (and some offer additional shooting modes such as 24p). Pocket camcorders, however, shoot only in standard definition or 720p.
Bit rate Bit rate describes the amount of information stored in a unit of time. For example, HDV, which uses the MPEG-2 encoder, offers a maximum bit rate of 25 Mbps (megabits, or millions of bits, per second). AVCHD, which uses the H.264 encoder, maxes out at 24 Mbps. The higher the bit rate, the better the video should look.
You can’t compare the bit rates of different encoders, as each encoder has its own way of processing video. For example, H.264 is a more efficient encoder than MPEG-2, so it produces better-looking video at lower bit rates. When comparing camcorders, you can compare the bit rates of two AVCHD camcorders, for instance, but not of an AVCHD and an HDV camcorder.
Media transfer Today’s camcorders routinely transfer data via a USB 2.0 connection. This is good news for people with one of the most-recent MacBook models, which lack a FireWire port. Unlike full-size camcorders, which include mini-USB ports, pocket camcorders have full-size USB connectors. A push of a button usually releases the connector so it’s ready to plug into a USB 2.0 port. For cameras that use removable media—an SD card, for example—you can optionally eject the media from the camera and plug it into a card reader attached to your Mac or PC.