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25fps vs. 24fps


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#1 Joel Balik

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Posted 22 January 2011 - 10:00 PM

Just curious. Is it significantly different in motion? I've never shot in PAL. How close is it to regular 24fps? Thanks
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#2 John Young

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Posted 22 January 2011 - 11:01 PM

As I understand, the only difference is when you go to line audio up.
There should be no perceived difference in what you see (from what I have seen).

If you shoot 25fps, and then go to do audio sync, in the US anyhow, there is (I think) a 4% different.
Someone smarter should chime in here.
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#3 David Mullen ASC

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Posted 23 January 2011 - 12:16 AM

Just curious. Is it significantly different in motion? I've never shot in PAL. How close is it to regular 24fps? Thanks


If you shoot at 25 fps and show at 25 fps, then motion-wise, it's not really different than 24 fps shown at 24 fps. The main difference is that for TV broadcast 24 fps is shown with a 3:2 pulldown at 60i, whereas 25 fps does't need a pulldown to be shown at 50i.

If you are talking about how 25 fps looks shown at 24 fps, it's a very slight slowdown, more noticeable in the audio pitch than in motion.
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#4 Joel Balik

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Posted 23 January 2011 - 12:19 AM

Since 24FPS is universal, and "24P" is the film trend standard for digital, then it's ok for Europe since the project would have to be converted to pulled up or down to 25fps? For instance films can be converted to any region format worldwide correct? That's how the general were/are able to watch films in 30p or 25p.

I'm just so confused with format restrictions. I just assume that when you publish a project you have the options to render to whatever format you wish. Therefore, does it matter nowadays with HDTV (or digital) to get the correct region? I've heard that marketers are still taking advantage of consumers knowing that most are now HDTV.

If I shoot in 24P then I can publish to any format correct? Since 24p is 24fps. Films have to be converted.
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#5 Phil Rhodes

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Posted 23 January 2011 - 06:49 AM

Yes, but then if you shoot in 25 you can also just assume it's 24 and publish in any region.

Makes no difference, just make sure you can do the appropriate audio conversions.

P
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#6 Brian Drysdale

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Posted 23 January 2011 - 08:46 AM

In PAL countries they just playback 24fps films at 25 fps, so your running time is shorter.

Sound wise, you can do a pitch correction, although some types of music don't respond that well to the process, so you need to listen for problems during the correction process.

On a short film I made we shot at 24 fps, but because of AVID licensing issues had to post at 25 fps. We keep the sound at 25 fps because doing it at 24 fps meant that the female singer then sounded too high pitched when played at 25fps. The pitch correction sounded awful on her sustained notes, so we couldn't go that way.
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#7 John Sprung

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Posted 24 January 2011 - 02:58 PM

Just curious. Is it significantly different in motion? I've never shot in PAL. How close is it to regular 24fps? Thanks


Just look at any of the BBC shows that run in the U.S. on PBS. They're all shot at 25 and shown here at 24, it works fine. Likewise, all the U.S. shows that run there were shot 24 and shown 25. Both have been done for decades, no problem at all.




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#8 Joel Balik

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Posted 24 January 2011 - 10:25 PM

What if I shoot in 60i? Even more reliable? This is a digital realm yes
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#9 Brian Drysdale

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Posted 25 January 2011 - 03:41 AM

What if I shoot in 60i? Even more reliable? This is a digital realm yes


A rather less universal format, it really depends on your planned market. 60i is interlaced, so it will look more like video than using progressive frames. It really depends on your subject matter, which will work best for you.
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#10 John Sprung

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Posted 25 January 2011 - 01:41 PM

What if I shoot in 60i? Even more reliable? This is a digital realm yes


No, the worst possible choice. Interlace is an artifact of the analog broadcasting legacy. It's the hardest thing to convert to other frame rates. It messes up inter-frame digital compression. Converting progressive to interlace is easy and works well. So, work progressive, convert to interlace if a customer wants it.




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#11 Mei Lewis

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Posted 03 August 2017 - 08:33 AM

Does anyone have any newer thoughts on this?

 

 

I'm in the UK and I've always shot 25fps until now.

I occasionally shoot stuff that ends up on TV where I'm pretty sure shooting at 25fps is still the best option, but should I shoot stuff that I know will only be seen on the web at 24fps?

 

I have a related question which despite much research I've not been able to get a good answer to. Many computer monitors have refresh rates that aren't multiples of 24 or 25. My 3 monitors are all at 60Hz.

This seems to mean I'm never really going to get smooth motion. Why isn't this talked about more online? Am I missing something?


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#12 Stuart Brereton

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Posted 03 August 2017 - 10:00 AM

British TV conforms to the PAL standard, so yes, 25fps is the way to go. For the web, it probably doesn't matter as much what you shoot at, but 24fps is a tried and tested frame rate, so why not stick to it?

 

Computer monitors can be tricky things to get right. As you say, they often refresh at unusual rates. If your monitors run at 60hz then you'll need a 1/60 shutter speed. At 25fps, that's a 150 degree shutter. At 24fps, it's a 144 degree shutter. you may need to fine tune these numbers, if your camera allows you that level of control.


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#13 Mei Lewis

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Posted 03 August 2017 - 01:23 PM

Thanks Stuart.

 

With the computer monitor, I'm not talking about filming it, but watching content on it.

 

Any and all 24fps content is going to somehow miss or double frames as it's displayed. And I think 60Hz is a very common refresh rate for computer monitors, probably because of the 60Hz mains in the US and elsewhere.


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#14 Stuart Brereton

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Posted 03 August 2017 - 01:41 PM

Any and all 24fps content is going to somehow miss or double frames as it's displayed. And I think 60Hz is a very common refresh rate for computer monitors, probably because of the 60Hz mains in the US and elsewhere.

I think you might be imagining a problem where none exists. Assuming you're shooting digitally, 24 fps is actually 23.98 fps. When the 3:2 pulldown is added, this becomes 29.97 fps, which fits neatly into a 60hz (actually 59.94) world.


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#15 David Mullen ASC

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Posted 03 August 2017 - 02:20 PM

3:2 pulldown is added for interlaced-scan monitors showing 24 fps (23.976 fps) material at 60 Hz (59.94 Hz).  Computer monitors are progressive scan and refresh at all sorts of rates, some over 60 Hz so I don't think traditional 3:2 pulldown is used if the playback source is actually 24P.


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#16 Stuart Brereton

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Posted 03 August 2017 - 02:52 PM

You may well be right, David. It's been a while since I've had to deal with pull down in Cinema Tools, so maybe things have changed.

 

To respond to Mei's concern, unless you're actually seeing a problem with playback on your monitors, I wouldn't worry about it.


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#17 David Mullen ASC

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Posted 03 August 2017 - 03:02 PM

I actually don't know how a progressive scan monitor converts one frame rate to different display refresh rates if they don't fall into whole numbers (like displaying 24P at 48 Hz).   Does it blend some repeated frames together with the next frame?


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#18 George Ebersole

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Posted 03 August 2017 - 03:51 PM

I actually don't know how a progressive scan monitor converts one frame rate to different display refresh rates if they don't fall into whole numbers (like displaying 24P at 48 Hz).   Does it blend some repeated frames together with the next frame?

 

I bought a new Aptiva earlier this year just for casual viewing, and it actually displays the refresh and frame rate of every bluray I pop into the player.  With DVDs it displays the refresh rate only because most of that media was specifically designed for 3:2.


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#19 Phil Rhodes

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Posted 03 August 2017 - 05:55 PM

Computer displays (and things like cellphones and tablets) end up simply duplicating frames to ensure the video remains in sync with the sound. Theoretically they might also drop frames, but usually the computer display is refreshed faster than common video formats, so video frames get duplicated.

 

There is no specifically-designed duplication scheme in use. The video playback software probably doesn't even know what the refresh rate on the display is. Every so often, it decodes a frame and sends it to the video memory on the graphics card. Then, every so often, the graphics card sends the picture in that chunk of video memory to the monitor, just as it does when you're surfing the web. The interaction between those two events creates duplicated video frames but there is no design involved. It just works out that way. There's no particular intention to, say, show every 24fps frame three times on a 72Hz display, even though 24 x 3 = 72.

 

Now, as a practical matter, if you view 24fps video on a 72Hz display, you will generally get every frame three times, but there is no explicit synchronisation and occasionally you will see a video frame duplicated either twice or four times. This will happen with a frequency depending on the timing drift that exists between the computer's graphics hardware and its sound hardware.

 

It generally requires a lot of digging through menus to set up specific display refresh rates on computers, though it's usually possible to do things like 50Hz or 72Hz.

 

...all of which is why we use Blackmagic and AJA boards to output video.

 

P


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#20 Robin R Probyn

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Posted 03 August 2017 - 06:50 PM

Mei.. if your in the UK then I would just continue to shoot 25p..  you'll be fine for any display .. but have the benefit of not having to worry about flicker from any practical light sources .. particularly florrie lights.. etc..   


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