Page "Deinterlacing" Paragraph 3

Both video and photographic film capture a series of frames ( still images ) in rapid succession ; however, television systems read the captured image by serially scanning the image sensor by lines ( rows ).

In analog television, each frame is divided into two consecutive fields, one containing all even lines, another with the odd lines.

The fields are captured in succession at a rate twice that of the nominal frame rate.

For instance, PAL and SECAM systems have a rate of 25 frames / s or 50 fields / s, while the NTSC system delivers 29. 97 frames / s or 59. 94 fields / s.

This process of dividing frames into half-resolution fields at double the frame rate is known as interlacing.