Shooting 60P for 24P

[Boz]

So, I'm hearing how much the 720P mode rules over the 1080P mode on the GH1. That's fine since I was always planning to work at 720P regardless. I also hear that you can drop 60P footage into a 24P timeline and it pretty much works seamlessly - also good news. But this brings up a couple of questions:



If you shoot 60P with the intention of converting (or dropping) to 24fps, wouldn't the slowest shutter speed available be 1/60th?
Wouldn't 1/60th be the shutter speed be the desired speed to shoot at, not 1/120th?

The way I'm figuring this is to look at 1 frame of 24P footage. That is a single "photo" shot at 1/48th of a second. Now if you took a single frame of 60P footage and looked at that, wouldn't you want it to be as close to that 1/48 shutter speed as possible? Remember this is not a question of shooting 60P with the intention of using it as slow-mo footage at 24P, it's the intention to drop frames and watch it at 'normal' speed.

Any thoughts / guidance would be greatly appreciated.

[Nektonic]

I'm with you on this question Boz. Hopefully Kholi will eventually figure out the best settings for 60p meant for a 24p timeline.

[Kholi]

I've gotta do a retest on the shutter speeds tomorrow. mostly to help myself decide why it's letting me select and shoot 720/60P with a 1/30, 1/40, 1/50 shutter speed and what it's actually DOING, or what it's NOT doing.

I'm pretty sure those are inaccurate shutter speeds in video mode and the camera just isn't changing anything.

I'll get to the bottom of it asap by doing some conversion tests up to 1/120.

You'd definitely want it to look as close to 1/48th as possible, though.

[Nektonic]

You'd definitely want it to look as close to 1/48th as possible, though.

Thanks. That is what was throwing me, since in 24p you would shoot 1/48 for a normal look, I was then thinking that for 60p you would use 1/120, but then if you are going for a 24p master in the end then would it look more like proper 24p with 1/60 or 1/50 shutter?

So when you drop these 720 60p clips into your 24p timeline are there any adjustments or extra rendering before you can play them back? I remember when you first mentioned this method that you stated it was necessary to turn off motion blending. Also, does this only work with FCP or will the other NLE's allow a nice filmic 24p to originate from 60p? Any more info on this 60p to 24p process would be greatly appreciated.

[hunter richards]

Kholi- It looks like when I record 720/60p with anything less than a 1/60th shutter, the camera records 30p inside of 60p- each frame is doubled. But when Its at 1/60th (or higher), 60 unique frames are recorded. Give it a try and confirm.

[Ian-T]

I would think one would shoot for a 180 degree shutter no matter what frame rate you choose. So @ 24p...it will be 1/48 and @ 60p it would be at 1/120. This would keep the blur consistent...right?

[LizaWitz]

If you're shooting 60p to project at 24p, you want a 1/48 shutter, so that each frame is exposed for the same amount of time as if you were only shooting 24 fps. This is if you're dropping frames. Of course you can't have a 1/48 shutter when shooting 60p, so 1/60th would give you the max motion blur and the closest equivilent to shooting 24p.

If you're shooting 60p for a slow-mo effect, then you would use the 1/120th shutter to simulate a high speed film camera that is shooting at 60fps.

Motion blur is dependant solely on how much the object moves while the shutter is open. So in a situation where you're dropping frames to get 24p, but shooting 60p, to get the motion blur as if you were shooting 24p you'd use the same shutter you would be using if you were actually shooting 24p.

Clear as mud?

[Ian-T]

My name is mud. :P

[Kholi]

Kholi- It looks like when I record 720/60p with anything less than a 1/60th shutter, the camera records 30p inside of 60p- each frame is doubled. But when Its at 1/60th (or higher), 60 unique frames are recorded. Give it a try and confirm.

Damn that makes sense. I was wondering HOW it worked. Thanks man!

Did you try dropping the footage on the timeline and playing back? What's it look like?

[Boz]

Stu Maschwitz gave a great response to the 'shooting 60P for 24P' question over on the Rebel's Guide Forum:

http://rebelsguide.com/forum/viewtopic.php?t=2603

[Nektonic]

Stu Maschwitz gave a great response to the shooting 60P for 24P question over on the Rebel's Guide Forum:

http://rebelsguide.com/forum/viewtopic.php?t=2603

He also recommends that it is still better to shoot in real 24p if possible.

You guys are correct. Since you'd want each frame to have as close to 1/48th shutter blur as possible, and time is still 1:1 from record to playback, 1/60 would be the best you could do.

HOWEVER, be aware that when you convert 60p to 24p like this, you do so by dropping frames. And not a consistent number of frames — you'll drop one, keep one, drop 2, keep 1, drop 1, keep one, drop 2, and so on:

X _ X _ _ X _ X _ _ X _ X _ _ X _ X _ _ X _ X _ _ X _ X _ _ X _ X _ _ X _ X _ _ X _ X _ _ X _ X _ _ X _ X _ _ X _ X _ _

(that's 24 X's out of 60 characters)

Although it can be surprising how well this can work (it's how we converted 60i to 24p before there were 24p cameras), it's no substitute for shooting actual 24p. If you have 24p available to you, then use it!

-Stu

But as Kholi said, he can't tell the difference from doing this with his GH1 footage. I think the bottom line is if it looks right then it is a viable option. Same thing with compression, if it looks good one in motion, then don't worry so much if it doesn't look perfect when you scrutinize a single frame grab.

[Kholi]

I'll get some more eyes on the 60 to 24.

Also still have some more shutter tests to do with it.

It's quite possible that I'm wrong and my eyes are busted.

[Boz]

Thanks for all the testing, Knoli, it's much appreciated. A pretty easy way to test for 60P to 24P smoothness would be to shoot some highway or freeway footage of cars moving across frame at consistent speeds. I would think any sort of jutter or weird frame skipping would show up pretty clearly in such a case. Just a suggestion.

[Kholi]

Will do, Boz. I'll find out soon as I get my camera back and post my results.

[joe 1008]

You see the pulldown cadence to get 24p out of 60p every day - it's how 24p movies are reproduced on a 60i TV tube.

The VariCam also produces 24p with a pulldown over 60p. And nobody ever complained about it.

[Boz]

Well, consider me 'complaining' then, because I just did a test with SonicState's footage (I hope you don't mind Sam!), and unlike Kholi I can definitely see a difference between this and regular 24P:

http://www.vimeo.com/4548905

Notice the 'pulsing' as people walk? That's the conversion pattern as explained by Stu in the above thread. I find it highly noticable and not very pleasant to look at.

Edit: One more thing, this is not an artifact of Vimeo. My conversion footage looks the same. I believe you can download it from the link provided above to see for yourself.

[joe 1008]

Yes, I can see it clearly, too. Strange, it's very strong. Almost looks like a 30p to 24p conversion. But I personally don't have any experience with this kind of pulldown, so I can't judge it. Just wonder how the VariCam manages the trick.

[Isaac_Brody]

Well, consider me 'complaining' then, because I just did a test with SonicState's footage (I hope you don't mind Sam!), and unlike Kholi I can definitely see a difference between this and regular 24P:

http://www.vimeo.com/4548905

Notice the 'pulsing' as people walk? That's the conversion pattern as explained by Stu in the above thread. I find it highly noticable and not very pleasant to look at.

Edit: One more thing, this is not an artifact of Vimeo. My conversion footage looks the same. I believe you can download it from the link provided above to see for yourself.


Boz, that footage isn't 60P, it's 30P. When the shutter dips below 60 in 720P mode it shifts into 30P mode. That's why it looks FUNKY.

[joe 1008]

That must be the reason! It looked too jerky for a 60p to 24p conversion. By the way I found a quote from Barry Green where he explains how the VariCam works:

"For 24P, it runs the CCD at 24Hz, giving true 24p capture. Each frame gets written to tape either two or three times, alternatingly, so it does a 2:3 pattern on tape. Those frames can be removed when editing; FCP-HD can extract the "active" frames, ignoring the duplicate frames, leaving a 40mbps pure 24p file on disk. This system is necessary because the tape drive must, by definition of the format, record 60 frames per second."

So, though much better than 30p to 24p, a conventional 60p to 24p conversion might no be THAT smooth as it does a VariCam...

[Kholi]

I'll have a lot of 60 to 24P footage up tonight. Random stuff but then people can judge for themselves.

[joe 1008]

I'm very curious :thumbsup:

[Boz]

Boz, that footage isn't 60P, it's 30P. When the shutter dips below 60 in 720P mode it shifts into 30P mode. That's why it looks FUNKY.

Sorry, but you are mistaken; either that or my software is lying to me. This is file properties BEFORE conversion:

http://bozfx.com/pix/rebel/fps.jpg

I'll be happy to convert any other file, but this one showed it best.

[Kholi]

It's lying to you. And it's already been discussed and confirmed by GH-1 OWNERS that anything below 1/60 shutter is NOT actual 60P.

Dont' know why people aren't listening.

[Boz]

I didn't shoot the footage, so I don't know for sure. How do you know this wasn't shot at 60P? Was it posted somewhere? Anyway, I'm going to do some more tests with 60P footage to confirm. Trust me, I want to be wrong in this case.

[Kholi]

It was shot at 60P, and Sonic said that he shot with 1/30 shutter. That means it's not 60P. There's a thread up in the Discussion clarifying this all.

[Boz]

Ah found it! So much to catch up on. OK, I'll pull that clip down. Sorry about that misunderstanding. I'm doing new tests with 'confirmed' 60P clips now.

[holyzoo]

Aha... there's now a thread for this. Where do I begin. First off. We don't have to scrounge for GH1 footage to test technique and workflow. Just shoot 60p on the HVX200 and start testing away.

For reference, here's 24p native with 1/48th shutter speed:
http://www.holyzoo.com/content/dslr/HVX200_24p-720x405.mov

Now 60p shot with 1/30th and dumped into a 24p timeline is awful:
http://www.holyzoo.com/content/dslr/HVX200_60p-24p_onethirty-720x405.mov

Kholi mentioned 1/60th and that has come out decent:
http://www.holyzoo.com/content/dslr/HVX200_60p-24p_onesixty-720x405.mov

But it still looks stuttery to me. It could be said that it merely looks like 24p with a higher shutter speed. And that's cool if that's what you're after. But what if you wish for it be smoother? Slowing down shutter is not an option.

So I thought I'd try throwing motion blur on it using ReelSmart Motion Blur - http://www.revisionfx.com/products/rsmb/

Here's the result:
http://www.holyzoo.com/content/dslr/HVX200_60p-24p_onesixty_rsmb-720x405.mov

I think I've come to my conclusion on this, but I wanted to share the findings, because this has been a pain in the a** to figure out.

[stephenvv]

Thanks - good test - and for me, shooting 60p for 24p is a nogo. People do have different motion sensitivities - I see DLP rainbows etc. easily, so the stutter bothers me.

[holyzoo]

So, I did think of one last solution which would look very smooth, but you'd lose your sync. Conform 60p to 24p using FCP and Cinema Tools. The end result is just like slowing down 30p to 24p.

Only way I found to do it with HVX200 60p is the following:

Drop 59.94fps clip into a 29.97fps timeline in FCP, then export that out, then conform that exported clip to 23.98fps with Cinema Tools.

Does anyone have any ideas of a quicker process of doing this?

[holyzoo]

Twixtor Test:

720p60 shot 1/60th shutter. Dropped into a 60fps comp in After Effects. Dropped that comp into a 24fps comp and applied Twixtor to it.

http://www.holyzoo.com/content/dslr/60p_from_HVX200_Twixtor_to_24-720x405.mov

For anyone who has done any 30p to 24p Twixtor'ing, I'm seeing a clear advantage to converting 60p to 24p vs converting 30p to 24p. There's twice as much information from which to do its thing.

[Imaginate]

maybe this is where a PAL version of the GH1 is a better idea. 50p to 24p seems a more natural conversion.

[Kholi]

In the end, the 23.98 drop does look like 24 with a higher shutter. Certainly.

I like Holyzoo's examples of Twixtor and the Motion Blur. I'll try some twixtor as well to see what it produces.

Also going to give 1080/24 another run tomorrow and try Holyzoo's 60 > 29.97 Timeline then the 30P Conversion that Squig posted.

And do a 720/30P MJPEG to 24 conversion tomorrow.

[TrueIndigo]

I assume the MJPEG footage does not need a powerful computer like AVCHD for realtime editing? Will I be ok with a 3 GHz P4?

[joe 1008]

Thank you everybody! That was a highly interesting crashcourse of workarounds. Definitely PAL-people are better off.

Kholi: If you can, please try what happens with the 1080p aliasing when downscaling the 24p footage to 720p. (or running it through a antialiasing filter like there is in Compressor, for example.) Personally, I'm more scared about aliasing than about the RS.

[Boz]

Twixtor Test:

720p60 shot 1/60th shutter. Dropped into a 60fps comp in After Effects. Dropped that comp into a 24fps comp and applied Twixtor to it.

http://www.holyzoo.com/content/dslr/60p_from_HVX200_Twixtor_to_24-720x405.mov

For anyone who has done any 30p to 24p Twixtor'ing, I'm seeing a clear advantage to converting 60p to 24p vs converting 30p to 24p. There's twice as much information from which to do its thing.

This is definitely the best result I've seen thus far. Thanks for doing the test! Will twixtoring footage in any way affect audio sync? Just curious.

All of this pretty much confirms my workflow that I'm going to use:


Shoot 1080P whenever possible. Strip 60i wrapper and scale down to 720P.
Shoot 720-60P for high intensity or high detail shots. Convert to 24P.

Simple, yet effective. A perfect solution? No. But it will work for me. :)

[Kholi]

Five 720/60P Clips dropped into the timeline. ALl recoreded at 1/60 or 1/80 for light control.

Find three and I'll gives you an cookies.

http://www.vimeo.com/4582107

[Boz]

That clip is awesome. As I stated on Vimeo, you have single handedly restored my faith in the GH1. Though, for action shots I still think it will be trouble.

I'm too tired to go through the whole thing looking for those 60P clips. But since I didn't notice them straight away, I guess that's a good thing! Did you use final-cut for this? I'm having trouble getting it to read MTS files.

[Kholi]

The action stuff was 60P aside from that very last shot. Purposely used 1080/24 on that so II would know for a FACT it wouldnt' work. didn't hurt to try.

The 720/60 will be excellent.

and yeah, if you don't notice right away and you have to scrub to find it then I personally think that mixing 720/60 will be a great workflow.

I'm using FCP. Log and transfer. The original clips probably don't work well because the file structures are off.

You can't just upload one or two clips, you have to shoot what you want on the actual card and just upload the entire card. That's what sonic did on his latest stuff, check it out.

Oh and the stuff at the end -- rehearsal for my next GH-1 test.

[dcloud]

would buyinga pal cam (50p to 25p) be a better option? :)

[joe 1008]

would buyinga pal cam (50p to 25p) be a better option? :)

Should work better. All frames are in place, 1/50 shutter is almost the same as 1/48, and each frame has more data, you only throw away 50%. The only trade off is the slow down from 25p to 24p (and some danger of lightning flicher in a 60Hz environment maybe?)

But Kholis clip convinced me that in most situations you are fine with the 60p pulldown. Also downrezzing 1080p to 720p seems to quit or reduce many artefacts. (That's something I would like to know more about - Kholi, can you hear me?)

[Kholi]

720/60P, 720/30P both AVC-HD and MJpeg work fantastic for motion. Most of the artifacting that exists in 1080 isn't there. Aliasing, I'm not sure about. An uprez from 720 to 1080 with Instant HD will tell the tale for sure.

[holyzoo]

Five 720/60P Clips dropped into the timeline. ALl recoreded at 1/60 or 1/80 for light control.

Find three and I'll gives you an cookies.

http://www.vimeo.com/4582107

Excellent footage Kholi. I agree that 720p at the 1/60th shutter (haven't tried 1/80th yet) looks pretty smooth, especially with normal action. I might find myself gettin picky if it was a shot that allowed for extreme scrutiny. But, drawing on my core belief that content is king, if the material is compelling, nobody cares about the tiny details.

My guess on what was 720p is - 00:10, 03:08, and 3:17

[Kholi]

Pretty close!! I'll reveal which ones shortly.

And yeah I can ABSOLUTELY agree with you that when the motion needs to really be 24P, it'll be a 24P process or converting properly. Definitely can't argue with that.

[joe 1008]

Framerate conversion from 60p to 24p should work excellent, there's so much information (60frames & few blur at 1/60 shutter) that the software (Twixtor or Compressor) never has to do guesswork. IMO this is the best way to get 24p AND 1/48 shutter.

Editing on a 60p timeline allows you to convert the final clip, only. At about 1hour rendertime for 1 minute of footage many projects can be rendered over night.

[Kholi]

If there's a good process for doing the 60P to 24P more accurately please post it up!!! I'm goign to shoot all of my action this week at 720/60, with a few 1080/24 inserts.

[John Caballero]

I just did a test with 720p60 shot with the HVX to Edius 24p timeline and it looked pretty good to me. Barry Green uses Edius, I wish he would comment on this process and how to get the best results.

[joe 1008]

If there's a good process for doing the 60P to 24P more accurately please post it up!!! I'm goign to shoot all of my action this week at 720/60, with a few 1080/24 inserts.

All the Canon 5D MKII boards are full of that stuff. Most people get good results converting 30p to 24p with Twixtor or Compressor. But there are tricky situations, where the software doesn't correctly analize and interpolate the frames. There is simply a lot of empty space with lack of information at 30p. So at 60p it should work much better (but maybe it will render slower?). Compressor also renders motion blur, so you could get a 1/48 shutter in post. Don't know if Twixtor does so, too.

One experienced posters here with this tecnique is Lee Wilson; he mostly shows up in the 5D department, but he might do us the favor and comment here about framerate conversion.

[SonicStates]

I just did a test with 720p60 shot with the HVX to Edius 24p timeline and it looked pretty good to me. Barry Green uses Edius, I wish he would comment on this process and how to get the best results.

Yeah John, I'm on Edius too but my computer chokes with the avchd situation so I have to get rolling with either a new i7 machine (mainly because I like new toys) or fork out more for RAM on the xeon platform I am working on (it is embarrasingly under-equipped for this type of work).

Would also love to hear what Barry has to say.

[Jackson Miller]

What does 60p with 1/60th shutter speed look like if you decide to actually use that footage for slo-mo? I mean, normally you would shoot 1/120th if you were planning on using the footage for smooth slo-mo shots, right?. But if you shot all of your footage in 60p at 1/60th shutter speed, would you be fine if you decided to use some of that for slo-mo? How would it look different? Less sharp I guess... but what else? Say we are talking about filming a person running or filming a skate video. Would the slo-mos have the desired effect even though you aren't using 1/120th?

Thanks

[ydgmdlu]

What does 60p with 1/60th shutter speed look like if you decide to actually use that footage for slo-mo? I mean, normally you would shoot 1/120th if you were planning on using the footage for smooth slo-mo shots, right?. But if you shot all of your footage in 60p at 1/60th shutter speed, would you be fine if you decided to use some of that for slo-mo? How would it look different? Less sharp I guess... but what else? Say we are talking about filming a person running or filming a skate video. Would the slo-mos have the desired effect even though you aren't using 1/120th?

Thanks
The "film look" requires at least a 180-degree shutter, or in other words 1/120th shutter speed. Any slower, and it won't look right. Specifically, there will be too much motion blur. You won't like it at all. You can probably find some footage shot at 720p60 with 1/60th shutter speed posted in the footage forum. Using that you can do your own test.

[Jackson Miller]

Thanks man. Any links on how exactly that works? I'll have to do my own tests once I get it I guess.

I can't open .mts files though... at the moment.

[Jean Dantes]

Wait a second. Wouldn't it be that if I dropped 50P into a 25P timeline, it'd playback 50% slower?

[Jackson Miller]

No, not unless you tell it to by configuring it with cinema tools or similar before hand as far as I understand. Your timeline will basically turn it into 25 p. or 24 p.

[Tim Joy]

http://www.projectionfilms.com/sunlit/60-for-24.png


I've been trying to wrap my head around this 60 for 24 thing and made a little graphic to help visualize what it would look like. This graph shows one second, 60 frames on the top, 24 on the bottom.
As you can see, it doesn't always line up.
Does these minute differences actually make a difference? Obviously, the most it could be off is 1/120th of a second.
Do some conversions compensate for this?

[dmoreno]

there's 2 ways to do the conversion: by dropping frames or by interpolating/blending frame information.
If your NLE simply drops frames to go from 60p to 24p it will have to follow an irregular cadence: keep one, drop one, keep one, drop two... and so on. This makes the kept frames unevenly spaced in time, some people find this disturbing, most don't notice it at all. In shots with little motion it's almost imposible to notice. In shots with regular speed motion, such as a ball rolling from one side of the screen to the other or a car passing by, you could notice some jerkiness in the movement.
Other NLEs that do frame blending, or other that do the even more complicated frame interpolation, try to make one frame by "mixing" the information of every 2.5 frames in to one. This can result in a more fluid motion, but usually results in ghosting or strange artifacts.
A perfect conversion cannot be done because 60 is not a multiple of 24. Lucky PAL land users can do a perfect conversion from 50p to 25p by simply dropping every other frame. We NTSC people can do a perfect conversion from 60p to 30p.

[Boz]

That's a perfect description of the options and how they work, Dmoreno. I continually hear people say they'll shoot 30P/60P for fast moving shots (where mud can be an issue) on the GH1 then convert to 24P. Yet I've asked for good working samples of this and have yet to see even one. I think there are going to be a lot of surprised/disappointed people out there when they shoot and convert over to 24P. :-/

[dmoreno]

It certainly isn't as easy as "drop it on a 24p timeline" as some people have said. It can be done as easy as that, but the results may be less than perfect depending on the way the NLE handles the footage. Most people may find the conversion to work well, we are used to watch uneven cadences in 24p movies with 3:2 pulldown we've watched on TV since we were kids.
I am also waiting for some 720 60p footage to try the conversion myself and decide if it works for me.

[John Caballero]

I am also waiting for some 720 60p footage to try the conversion myself and decide if it works for me.

If it works for you thats what counts. Technology and software is so advanced and becoming more so that a lot of things are possible in post. The secret for pros at this stuff is always work with the right software and be good at creating with it.