Television Lines (TVL) and Megapixels (MP) are both units to measure the quality and size of an image or video. TVLs are used to measure analog cameras and MPs are used to measure IP (Digital) cameras. Although they both measure the same thing, each are uniquely different.
Wikipedia states that a "TVL is defined as the maximum number of alternating light and dark vertical lines that can be resolved per picture height." The higher the TVL, the more detailed the picture. Acamera that has720TVL will have 360 distinct dark vertical lines and 360 distinct white vertical lines.
Image Courtesy of Wikipedia.
These lines alternate horizontally across the screen the distance equal to the height. For example, a monitor that is 8 inches x 6 inches will display those 720 vertical lines over the span of 6 inches.
A Megapixel (MP) is a unit to measure the number of pixels in an image. A pixel represents a single color to define an image. Have you ever zoomed in on image on your computer and noticed the image getting distorted and began to see boxes? Those boxes are the pixels! Below we have taken our logo at 2MP and zoomed in 1000% on the M and you can see how the image is comprised of little squares or pixels.
Although this is simply a picture, the same technology applies to video. Much like Television Lines for Analog Cameras, the more Megapixels you have for an IP Camera, the better the image quality.
How do Analog (TVL) Cameras Compare to IP (Megapixel) Cameras?
In order to identify which is better we need to convert Television Lines into Megapixels. This process can be quite complicated as there are further considerations to be made, such as whether the camera or DVR is recording in interlaced or progressive formats. Camera types, lens types and camera settings can also impact the overall picture. However, the short answer is a 720TVL camera is roughly converted to 976x494 NTSC and 976x582 PAL. Using the NTSC format, that would yield only 482,144 pixels, or roughly .5 megapixels.
The table below illustrates how a 720 TVL camera would compare to other MP Cameras
Resolution Pixels Megapixels
976 x 494 482,144 .5 MP
1280 x 1024 1,310,720 1.3 MP
1920 x 1080 2,073,600 2.0 MP
2048 x 1536 3,145,728 3.0 MP
2560 x 1920 4,915,200 5.0 MP