In the video world, resolution specifications are packaged and labeled using nomenclature like “1080p” and “HD,” whereas in the realm of digital still cameras we tend to identify the various plateaus using raw numbers only. The danger inherent in using labels is that sooner or later the marketing guys run out of superlatives and the names get longer as technology progresses. We expect to see “Super Duper Extra High Definition” on the horizon soon, to be followed, no doubt, by SDEHD Mark II shortly thereafter.
In any case, video resolution has at least two tags: the vertical pixel count and alpha label. 1080p, for example, is also known as Full HD and has a vertical resolution of 1080 pixels. The “p” signifies “Progressive” scan and means that each image is captured as a full frame of video, the alternative to “i” or “Interlaced” video in which two consecutive fields are captured and reassembled into one full frame. Think of it as the difference between a pull-down window shade and horizontal window blinds. For photographers, the advantage of the Progressive scan system, clearly, is that each frame is complete and can be independently edited.
With a frame size of 1920×1080 pixels, this is the highest quality currently available. The Canon EOS 5D Mark II and Panasonic GH-1 are two examples of cameras that offer full-HD, 1080p video capture.
720p HD (High Definition)
The 1280×720 is more than adequate for most applications and delivers outstanding quality overall. The Nikon D90 and popular D5000 cameras are 720p.
HDV (High-Definition Video)
HDV is captured at 1440×1080 and displayed as Full HD (1920×1080).
SD (Standard Definition)
Popular because it is the de rigueur for Hollywood DVDs, SD offers 720×480 resolution that matches NTSC television rendering.
SVGA=800×600 and VGA 640×480
These labels are quite familiar to most still photographers who recognize that, although smaller, SVGA and VGA offer reasonably good quality (close to commercial DVD output) and are compact and easier to handle. You’ll find many compact digital cameras with these options.
Divide a VGA 640×480 frame into four equal portions and the result is a tiny quadrant that’s nearly worthless in terms of video resolution. QVGA, or Quarter VGA, has a niche as an e-mail attachment but really nowhere else.