Cinematography-Theory-And-Practice

Figure 9.14. Interlaced video consistsof two sets of alternating scanlines. Each set of scan lines is calleda video “field.”THE VIDEO SIGNALEven if you shoot mostly on film, it is essential to know the basics ofvideo. Today, nearly all editing and most postproduction are donein video, even for projects shot on film, and we can envision a timein the near future when virtually 100% of it will be.No matter how well designed and goofproof a piece of videoequipment is, it is still not a matter of point and shoot. Even if certainsystems are automated, this automation may have unwantedconsequences down the line. To understand video, it is necessary tohave an overview of the history of the basic video signal. Black-andwhitetelevision broadcasts began in 1936 in Britain and in 1939 inthe United States television had a 4:3 aspect ratio. This matched thestandard film projection frame of the time.Interlace VideoIn standard-def TV, this electron beam scans 525 lines (in the NorthAmerican system). Standard-def video is usually interlaced (Figure9.14). The odd-numbered lines are a field and the even-numberedlines are a field. This means that every frame of interlace video consistsof two fields. Interlace video is not nearly as common as it oncewas, as most modern equipment is progressive.Progressive VideoMost of the time you will be shooting progressive. In progressivevideo, the beam starts at the top and scans down line by line (1,2, 3, 4,and so on). Progressive has higher vertical resolution than interlace,but the main reason we use it is that it looks more film-like. Dramaticnarrative productions (films with a story and actors) are usually shot24P, meaning that it is progressive video at 24 frames per second; 24frames per second being the frame rate of film cameras.NTSC and ATSCNTSC is the standard-def television system used in the United Statesand some other countries almost since the beginning of television. Itstands for National Television Standards Committee. It is now beingreplaced by High Def digital television.In NTSC, each frame is made up of 481 horizontal lines that arevisible, plus another 44 lines that are blanked. These lines are blankedbecause they occur while the scanner beam is traveling back up tothe starting point at the top left of the screen. This makes a total of525 lines for each video frame.ATSC (Advanced Television Standards Committee) is the standardfor digital High Def television wide screen 16:9 images upto 1920×1080 pixels in size — six times the display resolution ofNTSC However, aspect ratios other than 16x9 are also supported.Interlaced video (I)Odd Field Even Field Both fields interlacedcinematography160