Digital video quietly discards most of its colour information, and you never notice
Human eyes pick up fine detail in brightness far better than in colour, and video engineers exploit that. A common trick keeps the brightness of every pixel but shares one colour value across a block of four, cutting colour data by 75 percent. The picture still shows every possible shade; it just changes colour at fewer points.
The name is simply Latin for I see. The technology grew out of mid-19th-century fax machines, and a mechanical scanner called the Nipkow disk was patented as early as 1884, though practical systems took decades more. Unlike film, which stores tiny photographs you can see with the naked eye, video turns pictures into electrical signals. For years it could only be broadcast live, until an Ampex team led by Charles Ginsburg wrote camera signals onto magnetic tape in 1951. Those recorders cost around 50,000 dollars in 1956, with each one-hour reel costing 300 more; Sony brought videocassette decks to homes in 1971.
Another old trick, interlacing, was devised to stop early screens flickering without sending more complete pictures. Each frame is split into two fields, one of odd-numbered lines and one of even, drawn one after another. That is why European PAL video is written 576i50: 576 lines, interlaced, 50 fields a second. Showing such a signal on a modern flat panel can leave comb-like streaks on moving objects unless it is carefully deinterlaced.
Speeds and shapes vary widely. Old mechanical cameras managed six or eight frames a second, film runs at 24, NTSC at 29.97, and new professional cameras exceed 120. About 16 frames a second is roughly the minimum for smooth apparent motion. Television screens moved from 4:3 to the wider 16:9 of high definition, while phones pushed vertical video from 5 percent of viewing in 2010 to 29 percent in 2015, according to investor Mary Meeker.
Digital formats eventually won. DVDs arrived in 1997 and Blu-ray in 2006, and tape sales dropped. Since 2013, Hollywood has used digital cameras more often than film ones.
Source: Video
