25 or 24 f p/s?

[Jack56]

Dear all,

I've got to make a film for my work as a teacher with children. It's gotta be a funny film. Last year I made one with the 60d and a 15-85mm lens. Now I will use the mark5dIII and a 50mm 1.8 lens and maybe the 100mm L lens as well.
In the menu I can choose for several recording sizes. On youtube I found settings of 1920 .. and 24 f p/s. They also show a possibility of 30 f p/s. On my camera I can choose between 25 and 24 f p/s.
Which one is the better choice? 24?
In this film I will put some old pictures from the children. The photos will be screen filling. When I film in 24 f p/s will the film be screen filling as well or will this film be shown in another format?
Thanks for reading my questions!

 

[pato]

Traditionally TV signals are PAL = 25 (Europe) FPS and NTSC = 24 (America). With todays much more modern TVs and not to forget computers, I'd go for 25 or if you have the choice, 30-60.
The Hobbit was filmed in HFR which is 48 FPS. Yes yes I know, there are people who don't like it, but I prefer sharp images when moving the camera.
Simply put, the more FPS, the sharper the image on movements, the more data on your hard disk.

 

[DFM]

The "what frame rate to use?" question gets as many arguments going as "is Canon better than Nikon?" - but unless you intend to broadcast your footage on a TV network or release a motion picture, there is no technical difference. Videos shot at 25/24/30/21.653781610 FPS will all play back just the same on a computer - indeed videos from iPhones use variable frame rates but nobody watching them would notice. Modern editing software can happily mix clips of different frame rates and render out something different at the end, if you want.

24 FPS is regularly claimed as "the frame rate movies use" but it's not true - the film stock may have moved at 24 FPS (chosen entirely to match the optical soundtrack) but the shutter in early movie projectors opens twice, so theater audiences were actually watching at 48 images per second. In Europe they used 25 FPS - no matter what anyone says, humans cannot see the difference between 25 and 24.

What you can see is the shutter angle - the ratio between the frame rate and the camera's shutter speed. If the shutter is only open for a small fraction of each frame, the images have no motion blur so the result is stuttery (Saving Private Ryan used that intentionally for effect, and early video cameras were notorious for it). The 'ideal' ratio is half, also known as "180 degrees" (literally half a circle, optical movie cameras had circular rotating shutters with a section cut away). If you shoot at 25 FPS, your shutter speed would be 1/50 sec. This creates enough motion blur to confuse the brain into seeing a continuous shot, without being too smeary. It's not a "rule", but it's a good place to begin (choosing 24 FPS you'd still use 1/50 as there's no 1/48 on a standard DSLR).

Because of this, you're stuck with the amount of light you can cram into the sensor for each frame - so one reason to use 24 instead of 30 FPS would be to eek out just a little more exposure in dark scenes; but the gain between 24 and 25 is barely noticeable. On the other hand, people often shoot at 30 FPS then play back at 24 to create a slow-motion effect - but only you know if that's something you need to do.

Shooting in very bright light with a wide aperture, you hit the problem of having too much light - film cameramen solve that with neutral density filters but if you don't have those, filming at 30 FPS will cut down the exposure on each frame and can be enough to solve that problem.

Aside from those questions, there's no particular reason not to use 24 on your camera, but it's not the most important factor in how your final result will look - the shutter angle and f/stop decide the "feel" of the movie, so don't get hung up on it.

 

[Jack56]

Thank you very very much for this information. Very kind of you to share and for the time you have taken for such a long response.
I will give it a go this coming week.

 

[mxma1]

I personally use 24 fps. But as stated above, it's really just preference and regional standardization.

 

[pato]

Youtube is upgrading, soon you can upload 48 and 60 fps: http://www.guru3d.com/news_story/60fps_coming_to_youtube.html

 

[pablo]

one note... ntsc is 30fps (more accurately 29.97)

if you are in a pal region shoot 25, if you are in an ntsc region shoot 30fps.

if you are going to reverse telecine onto s35 film for projection at the local multiplex shoot 24fps.

Just to pick up on another couple of points from earlier, in addition to frame rate video systems were traditionally split into fields, each of half a frame. This was primarily to save broadcast bandwith, but had the extra benefit of smoother motion perception, virtually no 'jello' effect, so although few would see a difference between 24 & 25fps, the difference between 25 complete frames and 50 split fields is very obvious. The film effect often means 'deinterlacing' the split fields.

Academic as the dslr derived eos cameras only shoot in progressive complete frames.

 

[Etienne]

I use 30 fps (29.97), 1/60 sec shutter speed. It is smoother than 24p