Television lines

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

[2] 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.

TVL is an inherent quality of a camera or monitor, influenced by the visual bandwidth of the transmission system used.

[3] Since analog transmission of video is scan line-based, the same number of horizontal lines is always transmitted.