Television lines

TVL is defined as the maximum number of alternating light and dark vertical lines that can be resolved per picture height.
EIA 1956 video resolution target, used to measure TVL

Television lines (TVL) is a specification of an analog camera or monitor's horizontal image resolution.[1] 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.[2]

Definition

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TVL is defined as the maximum number of alternating light and dark vertical lines that can be resolved per picture height.[3] 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 4 by 3 inches (10.2 cm × 7.6 cm) monitor with 400 TVL, 200 vertical dark lines can be counted over 3 inches (7.6 cm) width on monitor (Note that the 3 inches (7.6 cm) of monitor height is used rather than the 4 inches (10 cm) 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 for the PAL system, 525 lines for the NTSC system.[3]

The following table shows the horizontal resolutions of some analog video systems:[4][5][6][7][8][9]

System Television Lines
Luma Chroma
VHS,[4][5] EV, Video8[4][5] 240 30
EIAJ-2[4] 240
U-matic[4] 240
CED[4] 250
Betamax,[4] VHS HQ 250 30
SuperBeta[4][5] 280 30
U-matic SP[4] 330
NTSC broadcast[9] 330
Type A[4] 350 120
S-VHS[4][5][9], Hi8[4][5][6][7][8] 400 30
Quadruplex (NTSC)[4] 400 120
LaserDisc[4] 425 120
ED Beta[4][5] 500 30

Limitations

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Since analog transmission of video is scan line-based, the same number of horizontal lines is always transmitted. However, several factors impede the ability to display fine detail within a line:

  1. The camera or other source of material.
  2. The storage and processing of the picture.
  3. The transmission of the TV signal e.g. broadcast by radio or by cable.
  4. The reception and reproduction of the picture on a TV set.

See also

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  • Kell factor, 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

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  1. ^ Jack, Keith (2005). Video Demystified. ISBN 0-7506-7822-4.
  2. ^ "QA-70-1 Video Resolution Pattern (EIA-1956) Product Specifications" (PDF). Retrieved 24 May 2013.
  3. ^ a b "Overview and resolution". Wsc.monstercable.com. Archived from the original on 2013-07-17.
  4. ^ a b c d e f g h i j k l m n o "Video History". Video Interchange. Mar 29, 2010. Archived from the original on 2010-11-10. Retrieved August 20, 2007.
  5. ^ a b c d e f g Braithwaite, Lancelot (April 1989). "Hi8 debut sets a new 8mm standard". Video Magazine. pp. 23–27.
  6. ^ a b Beeching, Steve (2001). Video and Camcorder Servicing and Technology. Newnes. ISBN 0-7506-5039-7.
  7. ^ a b "Sony EV-S7000 Hi8 VCR Operating Instructions, Page 79" (PDF). Sony.
  8. ^ a b Damjanovski, Vlado (2005). CCTV: Networking and Digital Technology. Elsevier/Butterworth-Heinemann. p. 238. ISBN 0-7506-7800-3.
  9. ^ a b c Booth, Stephen A. (October 1992). "Pieces of 8". Popular Mechanics. p. 66.
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