Mass Media & Technology

25, 30, 60 Frames Per Second

Will we ever be able to capture motion in it's truest form? (December 2016)

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JA
james-2001
And it's possible to tell 59.94i/p from 50i/p too...


I find it harder to tell that difference. Though I can tell when it's 50hz shown on a 60hz monitor (like watching a DVD or the iPlayer through a PC)- I guess due to the 50>60 conversion.

Though I'm certainly someone who thinks 24/25/30p should be consigned to the dustbin, they really are relics of the past (as has been said- 24fps was picked because it was the lowest they could get away with 90 years ago and therefore the cheapest. Made sense then, makes sense when working with film, but makes little sense working digitally.- it's not like 50/60 on digital is significantly more expensive than 24/25, unlike with film), especially as we're getting to higher resolutions and bigger screens. Yet we're still sticking with framerates with noticable juddering and motion blur (which partly negates the high resolution)? Though instead we're in a period where TV producers are obsessed with sticking that look on pretty much everything (just why is it needed on daytime property shows, Gardener's World and the Antiques Roadshow for god's sake?).
Last edited by james-2001 on 11 December 2016 6:49pm
WA
watchingtv
When Emmerdale had their "car crash" week recently they used some different techniques that made the picture look really different- and really impressive. A shame they didn't stick with it afterwards- the sort of visual style you'd expect from big budget dramas, albeit still 50i. Really would be good to see more dramas that do look like that. The immediacy of video, with more high quality visual production techniques- something you never usually see.
...

Tuesday 20th, Emmerdale will be focussing on Ashley using similar techniques from the crash week.
CI
cityprod
Try shooting something at 24p with a fast shutter and very little motion blur and see how smooth it looks!


I don't have to. I go to the cinema often enough, and used to back in the days when they actually showed film, rather than digital cinema which is what most cinemas are now. I can't make out individual frames in a 24 fps movie. It's one thing to say that something looks demonstrably smoother, but quite another to actually prove it. And by the way, if you work it out, 1/24th of a second is actually longer than 40 milliseconds.
DA
davidhorman
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I can't make out individual frames in a 24 fps movie. It's one thing to say that something looks demonstrably smoother, but quite another to actually prove it.


It's not about being able to "make out" individual frames, and it's incredibly easy to prove. The difference is blindingly obvious to most people. It seems a few just can't tell, for whatever reason, but we're not making this up.

I made this test clip a few years ago (check that the quality setting says 720p60):



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And by the way, if you work it out, 1/24th of a second is actually longer than 40 milliseconds.


I don't recall anyone saying otherwise...
CI
cityprod
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A difference of around 40 milliseconds, cannot be percieved by the human eye, so it appears to be identical, happening at the same time. Hence why 24 frames a second (the standard movie frame rate) looks fairly smooth.


That's demonstrably untrue, since 50fps looks quite different to - far smoother than - 24fps. Anecdotally, I find I can tell the difference between 60fps and 50fps. I've never seen 120fps.


Ah, but did it really? Or did you know in advance that you were watching something shot at 50fps? If you did, then you basically pre-programmed your brain to automatically think it was better. We humans are amazingly good at fooling ourselves. When you start to think critically, that's when you notice things you didn't notice before, such as how we can program ourselves to believe something is better because it has more pixels or more frames.

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I'd suggest that once you're above about 120 fps, the extra frames add little to actual speed footage


Not true either - even higher frame rates would allow you to track (with your eyes) moving objects on a screen without motion blur.

*

The above is an approximation, of course, and assumes that the eye has an intrinsic 120fps shutter, and that the football takes one second to cross the screen (it's cropped horizontally, of course, but the vertical size represents the full height of a screen).

[/quote]

Approximation is fakery. We've seen approximations that didn't actually tell the truth at all. D2MAC vs PAL, Even the HD vs SD approximations in the early years were at best very dodgy.

And according to science, our eyes and brain are capable of handling and processing 60 fps, but again, show people a 24 fps movie, and I promise you, they will not be able to percieve individual frames, it will look like smooth motion. Hence why I think once you get above 120 fps at full speed, you're not going to actually change the quality of what people see.
DA
davidhorman
Ah, but did it really? Or did you know in advance that you were watching something shot at 50fps?


Yes it did really, and yes, I can easily tell whether or not I'm watching 25fps or 50fps even without being "primed." 50fps to 60fps is a little harder to spot, but I can do it. Anyone who's worked anywhere near the technical side of broadcasting will tell you the same. In fact, most viewers at home will tell you the same. They know the difference between "film" and "soap opera." Monty Python did an entire sketch on it in the 70s.

Why on earth do you think anyone even broadcasts at 50/60fps if no-one could tell the difference from 24fps?

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Approximation is fakery.


In this case, it's fakery with reasonably accurate science behind it which does portray how a 600fps video would be perceived, and how it would remove motion blur when tracking objects with smooth pursuit. I know what I'm talking about.
CI
cityprod
A difference of around 40 milliseconds, cannot be percieved by the human eye, so it appears to be identical, happening at the same time.

Eh? Where did you get that figure from? Research suggests that >240fps is required to create seamless motion for some individuals (fighter pilots have incredibly well tuned eye/brain combos)


The MIT research I saw suggested that at best we can manage 60 fps. Source for your 240 fps number?

And the original came from Mythbusters. Bullet fired vs Bullet dropped.



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Hence why 24 frames a second (the standard movie frame rate) looks fairly smooth.


Nope - 24 fps only looks fairly smooth (actually I don't believe it ever looks 'fairly smooth'), in most cases, because people shoot content that keeps it looking smooth. 24fps was chosen as the lowest frame rate (as film stock and processing was/is expensive - and the higher the fps the more you need per second...) required to work when sound was introduced. It's about as low as you can go. They had to get round the inherent flicker issues by showing every frame twice or three times during projection (double or triple shuttering)


Where are you getting this stuff from? Yes, 24 fps was chosen because it still looked smooth, and people couldn't percieve individual frames. The rest of the crap about double shuttering is nonsense.
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Even as low as 15 frames a second doesn't look jerky.

It can look horribly jerky... You rely on motion blur and slowing down camera moves, tracks etc. to stop the image breaking up into a sequence of stills.


I don't believe you, mainly because I play a game World Of Warcraft and often the video quality of the game drops to around 12 or 13 fps, and it can look a little stuttery, like I can actually see there are individual pictures, and 15 fps is similarly stuttery, but to call it jerky is plain old nonsense.

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I'd suggest that once you're above about 120 fps, the extra frames add little to actual speed footage, but for slow motion footage, recorded at say 480 fps and slowed down to 30 fps, you'd see things that you would never see full speed.


That's a different argument - as you are then changing the timebase of the signal. However 300fps is deemed the point at which returns fail to be useful. NHK think that 120fps with a bit of shuttering is pretty good for 8k, though if you went to 16k or higher you may need a higher frame rate (motion blur again)

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Hell, the Mythbusters used high speed cameras to great effect in their whole series, using frame rates from 500 fps to 50,000 fps, though mostly around the 1,000 to 10,000 fps range.

Apples and oranges though - as you are then replaying the high frame rate stuff at lower frame rates, and its the lower frame rate the eye is perceiving.


Duh! I know that! I was countering the argument that the higher the frame rate the better the picture, when frankly at best 60 fps is our limit. I was saying the only use for frame rates higher than 120 fps is when you do slow motion material, like Mythbusters did.
CI
cityprod
Even as low as 15 frames a second doesn't look jerky..


You try playing a FPS game at only 15 FPS.


World of Warcraft at 12 fps. Good enough for ya? If not, tough!
CI
cityprod
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I can't make out individual frames in a 24 fps movie. It's one thing to say that something looks demonstrably smoother, but quite another to actually prove it.


It's not about being able to "make out" individual frames, and it's incredibly easy to prove. The difference is blindingly obvious to most people. It seems a few just can't tell, for whatever reason, but we're not making this up.

I made this test clip a few years ago (check that the quality setting says 720p60):


Did that, and smell a rat. I checked how it looked as well at 30 fps, by watching it on the standard 480p setting. At that speed, they shouldn't look any different but the left hand looked far worse at 30 fps.

Sorry. Not buying what you're selling.
NG
noggin Founding member
I could clearly see the difference between 50p and 100p during the BBC IBC demonstration about 5 years ago... And the difference between 25p and 100p was like night and day.

To get the same level of detail on moving elements at 25p you'd have to use a 1/100th or 1/200th second shutter - which would look horrible (as you are then discarding 75% or 175% of the information in a sequence.

You can't set a frame rate just based on the motion you wish to track, you also have to consider the amount of detail you want to capture on moving objects. If you want to avoid motion blur you have to reduce your exposure time. If you do this at a low temporal resolution (i.e. low frame rate) you discard huge amounts of information, and create an unpleasantly jerky result. If you reduce the exposure time AND increase the temporal resolution (i.e. run at a higher frame rate) you get a much more pleasant picture AND decent detail on moving objects.

As spatial resolution increases, temporal resolution needs to also.

If you shoot the same scene at 25p with a 1/50th shutter (which would be normal 'film mode') and shoot the same scene at 100p with a 1/200th shutter you will see much more detail on moving objects at 100p and the same detail will be motion blurred at 25p.

If you shoot 25p with a 1/200th shutter, and 100p with a 1/200th shutter you sill get the same amount of detail and the same motion blur in both 25p and 100p but the 25p sequence will look horribly flickery compared to the 100p as the 100p will have 4 x 1/200th exposures for ever 1 x 1/200th exposure in the 25p sequence.

You will see the difference in both cases. I certainly have.
Last edited by noggin on 11 December 2016 10:36pm - 2 times in total
JA
james-2001
Why on earth do you think anyone even broadcasts at 50/60fps if no-one could tell the difference from 24fps?


And on a similar note, why would they bother filmising TV shows if you couldn't tell the difference?
JA
james-2001
Tuesday 20th, Emmerdale will be focussing on Ashley using similar techniques from the crash week.


Basically it's the look I think TV drama should be gravitating towards- video look, but with techniques to take it as far away from a 70s studio look as possible.

In fact it's the look that the first "Rock & Chips" episode was made with back in 2010, but for whatever reason they decided to filmise that at the last minute- albeit the 50i version did still appear on BBC HD (presumably BBC HD technically wouldn't accept deinterlaced 50i for broadcast becasuse of the resolution loss?), the Virgin Media iPlayer and the BBC One signed repeat.

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