Understanding the mechanics of video recording

on Saturday, March 8, 2008

It is the springtime of love as John and Marsha bound towards each other across the blossoming meadow. The lovers’ adoring eyes meet as they race to each other, arms raised in anticipation of a passionate embrace. Suddenly, John is distracted by a ringing cell phone and he stumbles, sliding face-first into the grass and flowers at Marsha’s feet. A cloud of pollen flutters away on the gentle breeze, irritating Marsha’s allergies, which erupt in a massive sneezing attack.

As this scene unfolds, light photons bounce off John, Marsha, the blossoming meadow, the flying dust from John’s mishap, and everything else in the shot. Some of those photons pass through the lens of your camcorder. The lens focuses the photons on transistors in the CCD. The transistors are excited, and the CCD converts this excitement into data, which is then magnetically recorded on tape for later playback and editing. This process, is repeated approximately 30 times per second.

Most mass-market DV camcorders have a single CCD, but higher-quality cameras have three CCDs. In such cameras, individual CCDs capture red, green, and blue light, respectively. Multi-CCD cameras are expensive (typically over $1500), but the image produced is near-broadcast quality. Early video cameras used video pickup tubes instead of CCDs. Tubes were inferior to CCDs in many ways, particularly in the way they handled extremes of light. Points of bright light (such as a light bulb) bled and streaked light across the picture, and low-light situations were simply too dark to shoot.