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This question is mainly about pre-2000 TV series created for CRT TVs, but a lot of it still applies for HD-TV content.

So TVs have been 60Hz/59.94Hz(NTSC) ever since their inception and an old video camera would shoot 60fps interlaced to match the refresh rate. However due to the low visual quality of video, most higher budget series were shot on film at 24fps and converted via 3:2 pulldown to match the 60Hz. Examples would be StarTrek or X-Files.

I can understand why they choose to not shoot film at the full 60fps, as that would require twice the amount of film stock and more light. However what I don't understand is why they went with 24fps instead of going for 30fps.

A 30fps framerate that can be displayed accurately on 60Hz TV seems to be the more obvious choice than going with 24fps and doing 3:2 pulldown that introduces unnecessary judder.

But as far as I know, no TV series was actually shoot at 30fps. Cheap soap operas went for video and 60fps, while all the ones that went to film used 24fps. Only recently with the rise of digital cameras, Youtube and Internet streaming there is now a substantial amount of 30fps content available, though most/all(?) of the big budget productions still seem to go for 24fps.

Why choose 24fps when the content is never going to be displayed in a cinema and most TVs still don't support native 24fps playback? Has there been any 30fps content on TV prior to the introduction of digital cameras and HD-TVs?

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There are two related reasons.

The first is that feature film production, from the 1920s onward when film cameras became standardized, was entirely designed around working at 24fps. Cinematographers learned to exercise fine control over exposure, image quality and depth of field by balancing shutter angle (how long the frame exposes--literally how wide the gap or gaps in the film camera's spinning shutter is), f-stop (the width of the iris inside the lense), film stock (faster but grainier vs. slower but cleaner) and filters (at a minimum, neutral density filters, which reduce light transmission to the film without altering color). There are some very complicated tables and a lot of rules of thumb built around balancing all these elements, and altering the frame rate throws still another problem into the mix. Meanwhile, it decreases the amount of footage that can be shot before the film magazine must be switched by 20%, and bumps up the cost of film stock by just as much. Timing, editing and sound sync processes were all designed around 24fps as the desired output. This adds up to a lot of infrastructure and know-how optimised for 24fps, in a high-pressure production environment where time is money, and small mistakes can add up to even bigger money.

But it was (and is) certainly possible to shoot at higher frame rates. It's simply not worth it, for an additional reason. If the goal is to gain a higher quality image on tv, higher frame rates can actually work against you. I went into this in an answer about the "Soap Opera Effect," but the bottom line for this question is that the "judder" introduced by duplicating those frames isn't usually very noticeable, but the increased overall "sharpness" of motion at higher frame rates is.

And now we're getting into opinion, but I believe it's partly cultural, and partly about how our lower vision system translates speed of motion into perception of safety or danger. 24fps feels more like a waking dream than a real situation. This isn't what we want for sports or videogames, but it's exactly what we want to wrap our fiction in.

  • I think this is closest to what I understand is the reason. In short, film looks better, and not just because of frame rates, but also because of contrast and intensity. Also, there was an entire industry of film and sound for film, including editors and editing tools, audio post engineers and tools, etc., etc. To make the best TV shows, you want the best people, and those people were trained on film, and the best tools are made for film. Film also lasts longer than the old magnetic tapes, and preserves all the quality that couldn't be easily recorded on magnetic. – Todd Wilcox Feb 22 at 18:32
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This question confuses three different things:

  • Filming using film cameras, at 24 frames per second
  • Filming using NTSC video cameras, which record at 59.94 fields per second, where odd-numbered fields contain the odd numbered scan lines and even, the even
  • 59.94 fields per second = 29.97 frames per second

Most TV shows in the US and Canada from the 60s through the 90s were recorded using video recorders at 29.97 fps (citation needed!) because recording direct to NTSC video is cheaper as the media can be reused if necessary and no developing is required. And film stock was intrinsically more expensive than DigiBeta tapes (say). (Note the problem in the UK that some early episodes of Dr Who from the 1960s were lost because the tapes were overwritten.)

The benefit of using film is that it has much higher resolution than NTSC, so shows shot on film can be digitized to newer platforms (which is why we can have great BluRay of movies from the 1930s but not from TV shows from the 1970s).

  • Odd and even lines are shoot and displayed at different points in time for video, thus you get 60 images per second with video. Film gives you 24 images per second. That aside, the question is why film at 24fps, why not 30fps? Unlike video cameras, film cameras have no fixed framerate and are regularly over or undercranked for slow motion or time lapse, thus 30fps seems the logical choice. – Grumbel Feb 21 at 23:17
  • Or, more closely reflecting physical reality, you get 60 half-images leading to 30 images. But my point is that the basis of your question is based on a false premise. – James McLeod Feb 21 at 23:19
  • 60 images, not 30. See my other comments. – Grumbel Feb 21 at 23:29
  • I have seen your other comments. They don’t make you right. Each field is half of an image. – James McLeod Feb 21 at 23:30
  • Why do you think we have combing problems and need deinterlacers when digitizing video? Hint: There is no full image in a frame, just two half images made at different points in time. – Grumbel Feb 21 at 23:36
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This is admittedly speculation, but one reason is probably that film cameras that shoot at 30 fps weren't readily available at the time. There's an entire industry set up for capturing and displaying film at 24 fps. So that of course still means spending money on conversion from 24P to 29.97i (or 25i for PAL). But the conversion has to happen anyway if you're shooting on film and delivering on video. So adding frame rate conversion to the step everyone is already doing is cheaper that making a new camera.

Plus, the conversion is probably done on the same hardware for many different shows, but they can't all use the same cameras at the same time. So the production companies would spend a lot more to buy new cameras for all of their productions, whereas they can buy fewer conversion machines and use them on all productions.

TL;DR - it's probably cheaper this way.

  • But the thing is, running a film camera at a faster frame rate is quite simple and cameras are frequently over- or undercranked for slow motion or time lapse effects. There is nothing in a film camera as far as I know that inherently locks them to 24fps and even if there was in the early days, that should have been overcome in the many decades that followed. – Grumbel Feb 22 at 17:22
  • Equipment to record NTSC at 30 fps has existed since the 1950s, and became affordable by the 70s. See en.m.wikipedia.org/wiki/Video_tape_recorder – James McLeod Feb 22 at 23:27
  • I'm specifically talking about film cameras, not video. My point is that while it's certainly possible to record to film at 30 fps (and has been for a while) the entire industry is set up for recording at 24 fps, and they have to do the conversion from film to video anyway, so might as well keep the cameras you already have and do the frame rate conversion while doing the conversion to video. – user1118321 Feb 23 at 0:37

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