CNET's quick guide to HD camcorders
By Lori Grunin, CNET.comFeb 05, 2007
Need to know
In most ways, shopping for an HD camcorder is just like trolling for an SD model, sorting through the various lens specs, media types, and body designs. But as you'd expect, there are some issues specific to HD to keep in mind as well.CCD aspect ratio and resolution
Though some manufacturers may stress that they're using a 16:9 aspect sensor, the sensor geometry matters only if its resolution is low. For example, a frame of 1080i video has dimensions of 1,920x1,080 pixels; since it's interlaced, the vertical dimension needs to be at least 540 pixels (the vertical lines are staggered and combined--interlaced--to produce a full 1,080-pixel image). So you'd want a sensor that's at least 1.04 megapixels: 1,920*540. But a 1.04-megapixel sensor with a 4:3 aspect ratio may have too few horizontal pixels and more than enough vertical pixels to produce the same total. That's why, say, Sony points out that the three CCDs used in the HDR-FX1, each of which has an effective video resolution of 1.08 megapixels, have 16:9 aspect ratios, but the company doesn't mention it for the 1.99-megapixel effective-resolution CMOS in the HDR-HC3.In short, if the sensor resolution divided by 1,920 is at least 540 (for 1080i) or 720 (for 720p), you needn't worry about its aspect ratio.
