mdia 308
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MDIA 308. Television. Television. Like film – television is actually a series of still images presented to the eye in rapid succession Earliest experiments in 1890s Italian monk – Casselli Pictures by wire. Television. Mechanical Television Paul Nipkow – scanning disk Nipkow disk - PowerPoint PPT PresentationTRANSCRIPT
MDIA 308
Television
TelevisionTelevision
• Like film – television is actually a series of Like film – television is actually a series of still images presented to the eye in rapid still images presented to the eye in rapid successionsuccession
• Earliest experiments in 1890sEarliest experiments in 1890s– Italian monk – Italian monk – CasselliCasselli– Pictures by wirePictures by wire
TelevisionTelevision
• Mechanical TelevisionMechanical Television
• Paul Nipkow – scanning diskPaul Nipkow – scanning disk– Nipkow diskNipkow disk
• John Loge BairdJohn Loge Baird– Scottish inventor working with BBCScottish inventor working with BBC– Launched the first system based on Launched the first system based on
mechanical scanningmechanical scanning
Nipkow diskNipkow disk
TelevisionTelevision
• Electronic television – cathode ray tubeElectronic television – cathode ray tube
• Vladimir ZworykinVladimir Zworykin– IconoscopeIconoscope
• Philo T. FarnsworthPhilo T. Farnsworth– Image DissectorImage Dissector
TelevisionTelevision
Electronic scanning
White lightBeam splitterBeam splitter
Cathode ray tube
White lightBeam splitterBeam splitter
Color TV screens
Television standards
• National Television Standard Commission (NTSC)
• Standard Definition (SDTV)• 4:3 aspect ratio• 525 lines of horizontal resolution• 30 frames per second• 60 fields per second• 2 fields per frame• Interlace scanning
Television standards
• High definition (HDTV)
• 16:9 aspect ratio
• 1080 lines of horizontal resolution
• 30 frames per second
• Progressive scanning
Magnetic tape recording
• Magnetic recording heads are transducers that convert electrical energy into magnetic
• Recording heads are electromagnets
• Audio current creates an alternating magnetic field
• The magnetic field is focused at the “gap” in the record head
Magnetic tape recording
Magnetic tape recording
• The fluctuations in the magnetic field are stored on tape by re-arranging the magnetic polarity of the “metal” surface of the tape
• The tape surface is made from powdered metals, like FeO2, or iron oxide (rust)
• The metals are attached to a plastic backing with binder (glue)
Magnetic tape recording
• Playback heads are constructed in a nearly identical manner
• During playback, a current is induced to flow in the coil of the head by the magnetic charges of the tape surface
Fundamentals of Audio Production. Chapter 6.
17
Analog tape recordingReel to reel
Videotape
• Ampex corporation invented the videotape recorder
• Allowed television programs to be recorded and “mistakes” could be corrected
Quadruplex Videotape
Quadruplex
Helical scan
Helical scan