24p or 23.976?

[mercer]

Recently picked up the FZ2500 and so far I like it. It seems like it is a mini GH4... except not so mini. As I am going through the settings and testing a few things I became curious if there are any feature, focus, or exposure differences with shooting in 24p as opposed to 23.976? I know you can only shoot DCI in 24p and I know for broadcast reasons it is easier to shoot in 23.976, but as far as other camera features, auto focus benefits, or exposure latitude... does it make a difference?

I figured a long search of the vast topics on the GH4 could yield the answers but I figured I'd ask first to see if someone has a quick answer... thanks.

[Cary Knoop]

No, for other features it does not make any difference. 

Also it is easy to go from one speed to the other by speeding up or slowing down the footage.  However if your footage is long you would want to resample the audio to match the speed adjustment.

 

[mercer]

4 minutes ago, Cary Knoop said:

No, for other features it does not make any difference. 

Also it is easy to go from one speed to the other by speeding up or slowing down the footage.  However if your footage is long you would want to resample the audio to match the speed adjustment.

 

Thanks Cary, do you mean VFR and slow/quick function? Or do you mean by having it at 60hz it is easier to go in and out of 23.976 and 60p?

[Zak Forsman]

I think he's referring to converting from 23.976 and 24, and vice versa. I do this all the time for clients that i make DCPs for and it's seamless. they typically deliver a 23.976 master that needs to be 24 to meet the DCI spec. and you could do the same with your camera originals if you knew you had to meet a specific framerate delivery requirement. I save the old Apple Cinema Tools app for this specifically. No one has made an app since (that I'm aware of) that makes the process as easy.

[Cary Knoop]

Just now, mercer said:

Or do you mean by having it at 60hz it is easier to go in and out of 23.976 and 60p?

I don't understand what you are asking here. How did the 60p get in the picture?

Generally to convert I would do the following:

Change between 24p and 23.976p

This is relatively easy, you just slow down or speed up your footage in your favorite editor.  For short scenes you do not need to adjust the speed of the audio but for longer scenes you have to.  You resample the audio, this is a perfectly harmless operation, typically you can, but do not need, to maintain pitch because the speed change is very low. 

Change from 24p (and 23.976p) to 60i

This process is called telecine and is relatively harmless but still it does degrade image quality.  For this you need to slow down 24p to 23.976p and then you turn every second of video into 3 fields (fields are half frames).  The result will be interlaced video.  You could optionally frame double that to 60p.

Change from 24p to 25p

You speed up the 24p to 25p.  This does have an impact on the duration of the video but it is the only option that does not severely impact image quality.  You need to resample the sound and have to remain pitch (the pitch change is much more noticeable to your ears than the speed up).

Change from 60i or 60p to 24p or 23.976p

This is a bad conversion and should be avoided at all cost. 

Deinterlacing video

Always use frame doubling, your result will be much better.  So convert 50i to 50p not to 25p and convert 60i to 60p not to 30p.

 

Generally I would advice to avoid blending, repeating or removing frames unless there is absolutely no alternative, because you image quality will degrade.
.

[mercer]

28 minutes ago, Cary Knoop said:

I don't understand what you are asking here. How did the 60p get in the picture?

Generally to convert I would do the following:

Change between 24p and 23.976p

This is relatively easy, you just slow down or speed up your footage in your favorite editor.  For short scenes you do not need to adjust the speed of the audio but for longer scenes you have to.  You resample the audio, this is a perfectly harmless operation, typically you can, but do not need, to maintain pitch because the speed change is very low. 

Change from 24p (and 23.976p) to 60i

This process is called telecine and is relatively harmless but still it does degrade image quality.  For this you need to slow down 24p to 23.976p and then you turn every second of video into 3 fields (fields are half frames).  The result will be interlaced video.  You could optionally frame double that to 60p.

Change from 24p to 25p

You speed up the 24p to 25p.  This does have an impact on the duration of the video but it is the only option that does not severely impact image quality.  You need to resample the sound and have to remain pitch (the pitch change is much more noticeable to your ears than the speed up).

Change from 60i or 60p to 24p or 23.976p

This is a bad conversion and should be avoided at all cost. 

Deinterlacing video

Always use frame doubling, your result will be much better.  So convert 50i to 50p not to 25p and convert 60i to 60p not to 30p.

 

Generally I would advice to avoid blending, repeating or removing frames unless there is absolutely no alternative, because you image quality will degrade.
.

Sorry, thought you were referring to a benefit of shooting at 23.976 vs. 24p... meaning it is easier to switch between frame rates 23.976 and 60p. So, you think even if shooting 24p, it should be converted to 23.976? If that's the case, then the only real benefit of shooting in true 24p would be the ability to shoot Cinema 4K? But you also have to shoot in 24.00 hz as well which can cause strobing... so I might as well just shoot in 23.976 at 60hz.

[Cary Knoop]

6 minutes ago, mercer said:

So, you think even if shooting 24p, it should be converted to 23.976?

It depends on the destination media. 

For broadcast you would probably have to deliver to 60i (although ATCS does have a 1080p24 standard to be converted to 60i during broadcasting but it is almost never used).  So in that case you would have to start with 23.976.

For Blu-ray you should render 24p instead of telecine it to 60i.

I really do not know what you mean by 60hz.

 

[mercer]

34 minutes ago, Cary Knoop said:

It depends on the destination media. 

For broadcast you would probably have to deliver to 60i (although ATCS does have a 1080p24 standard to be converted to 60i during broadcasting but it is almost never used).  So in that case you would have to start with 23.976.

For Blu-ray you should render 24p instead of telecine it to 60i.

I really do not know what you mean by 60hz.

 

Okay, thanks. By 60hz, I am referring to the NTSC frequency that the video is being recorded at. With the FZ2500, you must set your frequency to 24.00 hertz to record true 24p. You can only record Cinema 4K at true 24p. If you want 23.976, you set it to 60hz or 59.95 hertz to be exact.

Thanks again for your help. 

[Cary Knoop]

7 minutes ago, mercer said:

If you want 23.976, you set it to 60hz or 59.95 hertz to be exact.

I am not familiar with this camera but does it wrap the 23.976p signal into a 60i signal as some old model cameras still do?

If so you have be careful with editing your footage, if you do it right you get back a clean 23.976p video but if not it will be a blended or interlaced mess.

If you upload a second of video using 23.976 we can verify if that is the case.

 

[mercer]

1 hour ago, Cary Knoop said:

I am not familiar with this camera but does it wrap the 23.976p signal into a 60i signal as some old model cameras still do?

If so you have be careful with editing your footage, if you do it right you get back a clean 23.976p video but if not it will be a blended or interlaced mess.

If you upload a second of video using 23.976 we can verify if that is the case.

 

The camera was just released this week so I doubt it is in a 60i wrapper. It's basically a one inch sensor GH4 with a fixed zoom lens. 

[Cary Knoop]

Just now, mercer said:

The camera was just released this week so I doubt it is in a 60i wrapper. It's basically a one inch sensor GH4 with a fixed zoom lens. 

Thanks!

 

[mercer]

2 hours ago, Cary Knoop said:

Thanks!

 

No, thank you!

[jase]

15 hours ago, Cary Knoop said:

Change from 60i or 60p to 24p or 23.976p

This is a bad conversion and should be avoided at all cost. 

Cary, could you elaborate a bit? I always thought that recording in 60p and using that in a 24p timeline to have 2,5x slowmo is good practice?

[Cary Knoop]

Just now, jase said:

Cary, could you elaborate a bit? I always thought that recording in 60p and using that in a 24p timeline to have 2,5x slowmo is good practice?

Yes, for slow motion it is a great option! 

I was actually talking about converting 60p recordings to 24p while keeping the same speed. 

You wind up having to blend frames or remove them.

 

[jase]

Just now, Cary Knoop said:

Yes, for slow motion it is a great option! 

I was actually talking about converting 60p recordings to 24p while keeping the same speed. 

You wind up having to blend frames or remove them.

 

Forgive me my stupidity, but are you saying that I shouldnt use a 60p recording in a 24p timeline without applying slowmotion? E.g. only if I would apply the slowmotion it will look good according to your opinion? If yes, does the same apply to 50p files in a 25p timeline which is not slowed down?

[Cary Knoop]

Just now, jase said:

Forgive me my stupidity, but are you saying that I shouldnt use a 60p recording in a 24p timeline without applying slowmotion? E.g. only if I would apply the slowmotion it will look good according to your opinion? If yes, does the same apply to 50p files in a 25p timeline which is not slowed down?

Without slowmotion going from 60p to 24p is not going to look good, but sometimes you have no alternative. 

Going from 50p to 25p is not perfect either but a lot better than going from 60p to 24p because you do not need blending and the cadences are not disturbed.  You could skip every other frame and whether it remains smooth depends partly on the shutter angle. 

 

[jase]

Thanks, I will need to run some tests to see this for myself.