# Movie speed & TV **URL:** \ **Category:** Factual Questions\ **Created:** [February 13, 2003, 3:40pm UTC](https://boards.straightdope.com/t/movie-speed-tv/154844 "2003-02-13T15:40:28Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![ticker](https://avatars.discourse-cdn.com/v4/letter/t/d07c76/32.png) [@ticker](https://boards.straightdope.com/u/ticker)\ **Post date:** [February 13, 2003, 3:40pm UTC](https://boards.straightdope.com/t/movie-speed-tv/154844/1 "2003-02-13T15:40:28Z")
IIRC cinematic film is shot at 24 fps US TV runs at 30 fps European TV runs at 25 fps So how do they show movies on TV? Supplementary question: Is it more than coincidence that the TV rate is half the AC supply frequency in a given country? ---
**Author:** ![II\_Gyan\_II](https://avatars.discourse-cdn.com/v4/letter/i/bbe5ce/32.png) [@II\_Gyan\_II](https://boards.straightdope.com/u/II_Gyan_II)\ **Post date:** [February 13, 2003, 3:44pm UTC](https://boards.straightdope.com/t/movie-speed-tv/154844/2 "2003-02-13T15:44:54Z")
> [@](#): > > \*Originally posted by ticker \* > \*\*IIRC cinematic film is shot at 24 fps > US TV runs at 30 fps > European TV runs at 25 fps > > So how do they show movies on TV? I guess, they repeat some frames. > [@](#): > > Is it more than coincidence that the TV rate is half the AC supply frequency in a given country? Yes. ---
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [February 13, 2003, 3:51pm UTC](https://boards.straightdope.com/t/movie-speed-tv/154844/3 "2003-02-13T15:51:06Z")
It’s called [3/2 Pulldown](http://www.dvdfile.com/news/special_report/production_a_z/3_2_pulldown.htm): > [@](#): > > \*\*Simply transferring each film frame onto each video frame would result in a film running about 24.9% faster than intended; 29.97 film frames would be shown during each second rather than the correct 24. The clever solution to this problem is to repeat film frames periodically in a very straightforward but mathematically significant way; the resultant redundancy prevents the apparent speedup of the film when shown at the conventional video frame > > The telecine machine used to transfer film to video for composite D2 masters (which may be used for VHS cassettes, laserdiscs, and broadcast) projects film onto a video imager at 59.94 frames per second (identical to and synchronized with the video field rate) and repeats film frames in a recurring 3:2 pattern. In other words, the film frame sequence is A, A, A, B, B, C, C, C, D, D, and so on. > > The first film frame, A, is repeated three times and is recorded as field 1 and field 2 of the first video frame, and field 1 of the second video frame. The second film frame, B, is repeated twice and is recorded as field 2 of the second video frame and field 1 of the third video frame. The third film frame, C, is repeated three times and is recorded as field 2 of the third video frame and fields 1 and 2 of the fourth video frame. The fourth film frame, D, is repeated twice and is recorded as field 1 and field 2 of the fifth video frame. See the pattern? Repeat this sequence six times and 24 frames of film become 30 frames of video.\*\* ---
**Author:** ![blakeformayor](https://avatars.discourse-cdn.com/v4/letter/b/e47c2d/32.png) [@blakeformayor](https://boards.straightdope.com/u/blakeformayor)\ **Post date:** [February 13, 2003, 3:57pm UTC](https://boards.straightdope.com/t/movie-speed-tv/154844/4 "2003-02-13T15:57:22Z")
A device called a telecine takes the film and extrapolates the extra frames needed. It takes part of the frames and makes new ones. [This site](http://www.projectorpeople.com/tutorials/pulldown.asp) explains the process pretty well. As for your supplementary question, you’re right, it’s no coincidence. The AC frequency in fact controls the field rate of the TVs. IIRC, it was a political decision in Europe to prop up the copper mining industry by building a 50 Hz electricity system. We didn’t do that in America, so we used 60 Hz, which is why we have different frame rates on TV. ---
**Author:** ![ticker](https://avatars.discourse-cdn.com/v4/letter/t/d07c76/32.png) [@ticker](https://boards.straightdope.com/u/ticker)\ **Post date:** [February 13, 2003, 3:57pm UTC](https://boards.straightdope.com/t/movie-speed-tv/154844/5 "2003-02-13T15:57:31Z")
Interesting link **Fear Itself** , thanks.