Television lines (TVL) is a specification of an analog camera or monitor's horizontal
image resolution
Image resolution is the detail an image holds. The term applies to digital images, film images, and other types of images. "Higher resolution" means more image detail.
Image resolution can be measured in various ways. Resolution quantifies how ...
. The TVL is one of the most important resolution measures in a video system. The TVL can be measured with the standard
EIA 1956 resolution chart.
Definition
TVL is defined as the maximum number of alternating light and dark vertical lines that can be resolved per picture height.
A resolution of 400 TVL means that 200 distinct dark vertical lines and 200 distinct white vertical lines can be counted over a horizontal span equal to the height of the picture. For example, on monitor with 400 TVL, 200 vertical dark lines can be counted over width on monitor (Note that the of monitor height is used rather than the of whole monitor width).
TVL is an inherent quality of a camera or monitor, influenced by the visual bandwidth of the
transmission system used. It should not be confused with the number of horizontal scanning lines of such systems, which e.g.
625 lines 625-lines is a standard-definition television resolution used mainly in the context of analog systems. It was first demonstrated by Mark Iosifovich Krivosheev in 1948.
Analog broadcast television standards
The following International Telecommunic ...
for the
PAL
Phase Alternating Line (PAL) is a colour encoding system for analogue television. It was one of three major analogue colour television standards, the others being NTSC and SECAM. In most countries it was broadcast at 625 lines, 50 fields (2 ...
system,
525 lines 525-lines is a standard-definition television resolution used mainly in the context of analog systems.
Analog broadcast television standards
The following International Telecommunication Union standards use 525-lines:
* CCIR System J
* CCIR Syst ...
for the
NTSC
The first American standard for analog television broadcast was developed by National Television System Committee (NTSC)National Television System Committee (1951–1953), Report and Reports of Panel No. 11, 11-A, 12–19, with Some supplement ...
system.
Limitations
Since analog transmission of video is
scan line
A scan line (also scanline) is one line, or row, in a raster scanning pattern, such as a line of video on a cathode ray tube (CRT) display of a television set or computer monitor.
On CRT screens the horizontal scan lines are visually discernibl ...
-based, the same number of ''horizontal'' lines is always transmitted. However, several factors impede the ability to display fine detail within a line:
# The camera or other source of material.
# The storage and processing of the picture.
# The transmission of the TV signal e.g. broadcast by
radio
Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a trans ...
or by
cable.
# The reception and reproduction of the picture on a TV set.
See also
*
Kell factor
The Kell factor, named after RCA engineer Raymond D. Kell, is a parameter used to limit the bandwidth of a sampled image signal to avoid the appearance of beat frequency patterns when displaying the image in a discrete display device, usuall ...
, which limits the vertical resolution in analog television, and both horizontal and vertical resolution in digital television, to a fraction of the number of scan lines or pixels
References
{{Analogue TV transmitter topics
Television technology