In
video
Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) syste ...
, a field is one of the many still images which are displayed sequentially to create the impression of motion on the screen. Two fields comprise one video
frame
A frame is often a structural system that supports other components of a physical construction and/or steel frame that limits the construction's extent.
Frame and FRAME may also refer to:
Physical objects
In building construction
*Framing (con ...
. When the fields are displayed on a video monitor they are "
interlaced
Interlaced video (also known as interlaced scan) is a technique for doubling the perceived frame rate of a video display without consuming extra bandwidth. The interlaced signal contains two fields of a video frame captured consecutively. This ...
" so that the content of one field will be used on all of the odd-numbered lines on the screen and the other field will be displayed on the even lines. Converting fields to a still frame image requires a process called
deinterlacing
Deinterlacing is the process of converting interlaced video into a non-interlaced or Progressive scan, progressive form. Interlaced video signals are commonly found in analog television, digital television (HDTV) when in the 1080i format, some D ...
, in which the missing lines are duplicated or
interpolated
In the mathematical field of numerical analysis, interpolation is a type of estimation, a method of constructing (finding) new data points based on the range of a discrete set of known data points.
In engineering and science, one often has a n ...
to recreate the information that would have been contained in the discarded field. Since each field contains only half of the information of a full frame, however, deinterlaced images do not have the resolution of a full frame.
In order to increase the resolution of video images, therefore, new schemes have been created that capture full-frame images for each frame. Video composed of such frames is called
progressive scan
Progressive scanning (alternatively referred to as noninterlaced scanning) is a format of displaying, storing, or transmitting moving images in which all the lines of each frame are drawn in sequence. This is in contrast to interlaced video used ...
video.
Video shot with a standard
video camera
A video camera is an optical instrument that captures videos (as opposed to a movie camera, which records images on film). Video cameras were initially developed for the television industry but have since become widely used for a variety of other ...
format such as S-VHS or Mini-DV is often interlaced when created, whereas video shot with a
film-based camera is almost always progressive. Free-to-air analog TV was mostly broadcast as interlaced material because the trade-off of spatial resolution for frame-rate reduced flickering on
Cathode ray tube
A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms ( oscilloscope), pictu ...
(CRT) televisions. High-definition digital television (see:
HDTV
High-definition television (HD or HDTV) describes a television system which provides a substantially higher image resolution than the previous generation of technologies. The term has been used since 1936; in more recent times, it refers to the g ...
) today can be broadcast terrestrially or distributed through cable system in either interlaced (1080i) or progressive scan formats (720p or 1080p). Most prosumer camcorders can record in progressive scan formats.
In video editing, it is crucial to know which of the two (odd or even) fields is "
dominant." Selecting edit points on the wrong field can result in a "
flash
Flash, flashes, or FLASH may refer to:
Arts, entertainment, and media
Fictional aliases
* Flash (DC Comics character), several DC Comics superheroes with super speed:
** Flash (Barry Allen)
** Flash (Jay Garrick)
** Wally West, the first Kid ...
" at each edit point and playing the video fields in reverse order creates a flickering image.
See also
*
Federal Standard 1037C
Federal Standard 1037C, titled Telecommunications: Glossary of Telecommunication Terms, is a United States Federal Standard issued by the General Services Administration pursuant to the Federal Property and Administrative Services Act of 1949, a ...
: defines field in interlaced video.
*
Color framing
In video engineering, color framing refers to the color frame sequence of fields in a composite video signal through which the video frame timing and chrominance subcarrier signal timing—in particular, that of the color burst -- cycle through all ...
External links
All About Video Fields: technical information with emphasis on the programming implications of fields
{{DEFAULTSORT:Field (Video)
Television technology