Frame Rates and Flickering

Pal and NTSC Standards
Frame rates matter. The NTSC standard uses a frame rate of 30 frames per second, while the PAL standard uses a frame rate of 25 frames per second. The bottom line is that lower frame rates, as you would find with PAL, produce more flicker when the screen is interlaced.

[Background: the NTSC - National Television Standards Committee - was responsible for developing, in 1953, a set of standard protocol for TV broadcast transmission and reception in the United States. Another standard - Phase Alternation Line (PAL) - is used in other parts of the world.]

 *
Line flicker or "twitter"

Line flicker occurs when there is a sudden change in brightness between one scane line and the one above or below it, or when fine detail is fewer than two scan lines high. It gets worse during vertical movement as the fields alternate.The human eye sees this as a fast flickering. It appears as if borders of objects - including text - are jumping up or down. This gives text and images an unstable, jittery appearance.

Credits
* Images provided courtesy of Secrets of Home Theater and High Fidelity and Brian Florian. Please refer to Brian's informative article, "An Explanation of Film-to-Video Frame Rate Conversion for NTSC."

<< back • index • next >>