For example, if a camera was pointing at railings in a park and there were 420 railings across the width of the image, you would need a 420TVL camera to be able to count all the vertical railings.
TVL is commonly confused with the number of Video Lines on a screen, ie 625 for PAL (and the other HD formats 720, 1080i etc.)
Lenses, cameras, recorders and monitors have a TVL ratings and should be considered as a total system.
VL – Video lines. The number of horizontal scan lines in an images.
Typical pixel dimensions:
|480 TVL||510 x 492|
|600 TVL||768 x 494|
|650 TVL||811 x 508|
|700 TVL||976 x 582|