Recording file format: Most camcorders save video to flash drives or another form of on-board storage, using the AVCHD (Advanced Video Codec High Definition) format.
The AVCHD format isn't as "lossy" as standard MPEG-4, restoring the original video to much of its original clarity and sharpness after compression and decompression. However, you need a powerful computer to handle the complex decompression process. Your PC should have at least a 2GB multicore processor with 4GB of RAM for smooth (or at least not too painful) AVCHD file editing.
AVCHD has finally reached prime time. Most video editing programs now support it. Most AVCHD camcorders can record high-definition video at a bit rate of 24 mbps, producing video that virtually matches the quality of MiniDV tape cameras that use the HDV recording format.
Screen: The camcorder's LCD screen lets you see more easily what you're recording and lets you watch playback previews. Obviously, the bigger and higher-resolution it is, the better, but a bright, big screen will take a toll on your battery life.
Be careful when considering a camcorder's screen: Some don't work well in bright sunlight, an environment where you'll often use the device. It's more important than ever to choose wisely, because camcorder makers have dropped the viewfinder off of most of their consumer-level models, leaving the LCD screen as your only viewing option. What's more, some LCD screens offer a touchscreen interface for most in-camera controls, so try to get some hands-on time with the camcorder before you buy to make sure that any touch interfaces are responsive and intuitive.
Lens: Beyond the realm of pocket camcorders, every camcorder comes with a zoom lens that lets you get closer to your subject. Camcorder manufacturers don't always distinguish clearly between digital and optical zoom. The spec for maximum optical zoom is the more interesting figure: It gives the maximum zoom that the camcorder can achieve by moving its lens elements. Most modern camcorders have at least a 10X optical zoom, which should be more than adequate for general purposes.
A digital zoom crops and magnifies your footage after the optical zoom is fully extended, as the camcorder enlarges part of the image to fill the screen. This method leads to grainy, pixelated, and generally unpleasant-looking images. Sometimes, the quality is so poor that you can't see what you're taping.
Image stabilization: All camcorders perform one of two types of image stabilization--optical or electronic--to reduce jittery video caused by shaky hands. With optical stabilization, the camcorder's lens mechanism moves to compensate for external movement. With electronic image stabilization, the image captured by the lens "floats" on the sensor, and the camcorder uses internal circuitry after the image has been captured to interpret the video. Optical stabilization usually provides better results; in the past it tended to appear on more-expensive camcorders, but these days some moderately priced models have it too.
Batteries: The amount of recording and playback time you'll get out of a battery varies, but most camcorders should be able to record for at least an hour with the included battery. It's always a good idea to buy an extra battery and bring it with you on a long or important shoot; and keep in mind that repeatedly reviewing the footage you just shot will drain your camcorder's juice quickly. Additional higher-capacity batteries typically cost from $50 to $100.
Microphones: Sound can be as important to a video as image. We've found that camcorders with microphones mounted in the front tend to produce better sound than those with microphones on top of the unit. Top-mounted microphones often pick up the voice of the person operating the camera, drowning out everything else. Some camcorders offer zoom microphones that emphasize the subject's voice when the zoom lens is used, and some come with a socket for plugging in an external microphone. Either type of microphone can be very useful for recording presentations or speeches.
Still photography: Many digital camcorders can serve as digital cameras, saving still images to a memory card or to tape. Some can save images at the same resolution as a 12-megapixel camera (but watch out for models that produce interpolated high-resolution images from lower-resolution sensors). Nevertheless, none of the camcorders we've tested has performed as well at taking still pictures as a dedicated still camera—they simply don't provide the same level of control or the same image quality.
Controls: We have found that smaller camcorders can be a little more difficult to use because their controls don't naturally sit where your fingers fall, particularly if you have large hands. Of course, heavy, bulky models can become tiring to carry, so strive for a balance.
Low-light modes: Many camcorders have the ability to film in very low light, whether by using a special slow-shutter mode that makes the most of ambient lighting, or through built-in illumination from one or more LEDs. A few models include an infrared light that lets you film in total darkness, but these are generally going the way of the dodo. Low-light modes can be very useful in poorly lit settings, but video captured with these tools enabled won't look as good as video captured in bright or sunny locations. For example, slow-shutter modes may cause moving subjects to "smear" or "ghost," and infrared footage has an otherworldly effect, too (think Blair Witch Project).