The “3:2 pulldown” conversion process for 24 frame/s film to television (telecine) creates a slight error in the video signal compared to the original film frames.
This is one reason why NTSC films viewed on typical home equipment may not appear as smooth as when viewed in a cinema. The phenomenon is particularly apparent during slow, steady camera movements which appear slightly jerky when telecined.
This process is commonly referred to as telecine judder.
PAL material in which 2:2:2:2:2:2:2:2:2:2:2:3 pulldown has been applied, suffers from a similar lack of smoothness, though this effect is not usually called “telecine judder”.
In effect every 12th film frame is displayed for the duration of 3 PAL fields (60 milliseconds) – whereas the other 11 frames are all displayed for the duration of 2 PAL fields (40 milliseconds). This causes a slight “hiccup” in the video about twice a second.
Television systems converters must avoid creating telecine judder effects during the conversion process.
Avoiding this judder is of economic importance as a substantial amount of NTSC (60 Hz, technically 29.97 frame/s) resolution material that originates from film – will have this problem when convered to PAL or SECAM (both 50 Hz, 25 frame/s).