What is TVL in relation to Security Camera Specifications?

Question
What does TVL mean and why is it important.

Answer

TVL stands for TV Lines and relates to the resolution of an analog security camera.

It can be referred to as the Capture or Camera resolutions.

When reading a security camera specification sheet, you will see two sets of numbers rating the sensor of the camera. One lists the number of pixels (768 H X 494 V) for the sensor and the other rates the horizontal resolution (TVL) of the camera.

Effective pixels = 768 (Horizontal) X 494 (Vertical) Horizontal resolution = 540 TV lines

The difference between the two is pixel aspect ratio and picture aspect ratio. The pixel aspect ratio has to do with the actual number of pixels that sensor is able to capture. The picture aspect ratio is based on what the NTSC standard for analog signals (composite video) has been designed to process. The numbers are different but using the math behind it you can calculate how the two relate. We will avoid the math for this discussion.

Hope that clears things up some. Feel free to leave your comments below.