Project in 24fps with 23.976fps footage

[ggobb]

Hello everyone,

We're starting to shoot a documentary that is intended for theatrical release, so the instinct is to shoot at 24fps. However, we have a lot of research material that will likely (at least in part) end up in the film. All that material was shot in 23.976fps, as the camera we used was not capable of pure 24fps. Considering that the output will be in 24fps, is it best to shoot the bulk of the film in 24? Or should we stick to 23.976 to avoid mixing framerates on the timeline?

I know that neither is ideal, but I am trying to figure out which one of the two options is the best way forward.

Thanks everyone!

[R Neil Haugen]

Most cameras that list "24fps" actually record 23.976. So you should check either in the MediaInfo utility applet or the Properties panel, or in the bin in List mode if you have the FPS set to show in metadata. The difference between 23.976 and actual 24 is so slight I've had numerous working pros say ignore it unless it's a long file or you have a broadcast rejection.

[ggobb]

Hi Neil, thanks for your reply. A couple of things:

- The camera definitely does pure 24fps (we are upgrading from a FS5, which did only 23.976, to the FX6 which can do both!).

- Maybe I should have mentioned that the film uses very long takes (sometimes 1, 2 or 3 minute long), so it would probably experience some dropped frames at some point.

So would you say that the best thing is to shoot the best thing is to shoot everything else in 24 as the output is 24 (and therefore have mixed framerates in the timeline)?

Thanks!

[R Neil Haugen]

The answer is ... probably. My mixed-fr question of the Facebook pro editor's group, a very experienced group across broadcast especially  ... got the answer that normally most of them just drag/drop stuff on, and it works.

Especially for 23.976 to 24. It takes quite a lengthy shot before anything seem off.

It's going to 29.97i that can be ... iffy, at times.

[ggobb]

Wonderful Neil, thank you so much!

[Remote Index]

Hi ggobb,

You do have to decide if you are going to edit and master in either 24fps or 23.976fps (as you have indicated in the premise of your post).

To review some basics:

When you have any sort of frame rate mismatch - where the media does not match the sequence frame rate - then Premiere Pro performs a frame rate conversion in the timeline: the media clips in the timeline are transformed to match the sequence frame rate. There are 3 versions of this:

PREMIERE PRO FRAME RATE CONVERSIONS - 3 OPTIONS

A. "QUICK AND DIRTY" (“FRAME SAMPLING”)
If you simply drag your clips into the timeline, Premiere Pro does what I call a fast and dirty frame rate conversion. It will simply duplicate or drop frames to achieve the necessary frame rate. (You may need to render).
You will experience dropped frames if you use 24fps media in a 23.976 timeline.
You will experience doubled frames if you use 23.976 media in a 24fps timeline.

B. "FRAME BLENDING"
If you right-click on a clip in your timeline and choose "Clip Speed/Duration" you will see options for "Time Interpolation" at the bottom of the dialog. The above "quick and dirty" method is the default (known as "frame sampling" here). The second option is "frame blending" which does what it says ... combining or blending frames to create new ones. You probably have to render the clip after.

C. "OPTICAL FLOW”
This is the third option in the dialog. This option uses software magic to analyze existing footage and create new frames as necessary. You will likely need to render the clip after. Depending on the footage, it will either be amazing or heavily artefacted (unusable) or somewhere in between.

The first method is the one that you are most likely to use in cases like this.

In practice, the two frame rates are of course very close - between 23.976fps and 24fps, there is only 1 frame difference for every 1000 frames. That means if you have clips in the timeline less than 1000 frames in duration, you're not likely to see any "frame rate conversion". For longer clips, you'll be able to track where the frames are doubled for 23.976fps media in a 24fps timeline (every 1000 frames) in a "quick and dirty conversion". This may be sufficient for your needs.

PROJECT PLANNING

The above issues aside, you can think about three options in approaching your project.

1. STANDARDIZE ON 23.976 FOR SHOOTING
Since existing footage uses this frame rate, you can shoot to match.
Your master at the end will be 23.976

2. STANDARDIZE ON ONE OR THE OTHER AND CONVERT FOOTAGE
Another way to handle all this would be to decide on a standard (24fps or 23.976fps) and use “Interpret Footage" on media before you use it in the timeline - effectively speeding up your 23.976 material to 24fps or slowing down 24fps to 23.976. (Note that Adobe does not support use of “interpret footage" with its built in proxy workflow.)

 3. IGNORE THE ISSUE UNTIL YOU PICTURE LOCK
Another way of working would be to ignore the frame rate conversion while you edit (relying on the "quick and dirty' method) and then once you have picture locked, deal with material on a clip by clip basis - either refining the frame rate conversion (with methods B or C, or other methods), or going back to source clips and using "interpret footage" to correct the frame rate and re-cut it into the timeline (allowing for slight differences in media on the new, interpreted footage). This may require some minor picture adjustments depending on the length of your shots (see the 1000 frame rules above).

Hope that helps.

R.

[R Neil Haugen]

Excellent post!

To add, 1,000 frames at roughly 23.976 is just above 40 seconds. If you don't have any clip over 40 seconds, you won't see that addition or cut ... and even if there is one, most of the time no one will notice.

I've heard editors say that if they need to, they simply add a cut to a longer clip on the sequence, and as Premeire then grabs the two shorter bits, rather than one longer one, there's no double or drop. 

And others just said unless there's a lot of money on it, no one's gonna notice one or two drops or doubles in a half hour show.

So ... like so many things, you can do stuff to avoid the situation ... but you may not even need to with short clips ... and realistically, who's gonna notice anyways?

Choices. All work at least mostly.