They Call This High-Def? When Small Means Less
Not All HD footage is created equal. High-definition pocket camcorders make compromises in video quality so as to shrink the cameras' cost and size. Here's a rundown of the major limitations.
Lower-quality lenses: Tiny, simple lenses grab less light and provide less light control than lenses on bigger HD camcorders.
Tiny imaging chips: Light gathered by the lens hits a single, tiny (typically 1/4.5-inch) CMOS chip that packs many photosite sensors into a small area. Bigger HD camcorders usually have bigger and/or multiple imaging chips. On pocket HD camcorders, fewer photons hit each photosite sensor, resulting in compromised images in low-light situations and other tricky conditions.
Fewer pixels: Pocket HD camcorders typically generate 1280- by-720-pixel images; the Sony Webbie HD can create 1440-by-1080-pixel images. Full-size HD models can capture 1920-by-1080-pixel footage, and those higher-resolution source images generate better final images, even when delivered at lower resolutions.
Weaker image processing: Bigger camcorders are built with intricate image-processing systems to control colors, reduce noise, and improve image quality under varying lighting conditions. The image processors in pocket HD camcorders, on the other hand, come with much more limited processing power.
More (and coarser) compression: Creating great-looking video with the H.264 codec requires more processing and a higher bit rate than minicamcorders can provide; most pocketable models compress video at about a 9-MBps bit rate. Larger HD camcorders use AVCHD compression (also a form of H.264), which provides better, lighter compression. Their bit rates (and file sizes) can be two to three times those of pocket HD camcorders.
Tough shooting conditions: The more complex the scene, the greater the difference in image quality between pocketable and full-size HD camcorders. Pocket models struggle to create good video in conditions of low light, high contrast, and fast or extensive motion (including motion that is introduced by unsteady hands).