Trying to settle something about 60fps to 24

[Chris Tompkins]

Once the clip is in the proj. “right” click and choose; interpret footage.

Choose the frame rate you want to play it back. Then drop into the sequence. Do this before you apply a slow down% on a clip in the sequence. See pic:

Chris

[Richard Herd]

[Sean Winn] ” I’ve shot 60 for slo mo “

Are you familiar with over cranked footage? In order to have actual slow motion, you need to have a camera that shoots over cranked. Calling it “over cranked” is an historical term from when film cameras were hand cranked. If you cranked it too fast then it created slow motion (and wasted some film), when played back at 24fps. If it was under cranked, it created a funny sped up effect, when played back at 24fps.

To state the obvious, to make an exposure, a normal still camera needs three things: (1) ISO, (2) Aperture, (3) Shutter speed.

In motion capture, the shutter speed is a product of the shutter angle and the shutter rate (Rate * Angle = shutter speed). Panasonic cameras call the Shutter Angle Synchro Scan.

A few examples:

Frame Rate=1/24
Shutter Angle (which is a circle) = 180/360 = 1/2

1/24 * 1/2 = Shutter Speed = 1/48

Frame Rate = 1/60
Shutter Angle = 180/360 = 1/2

1/60 * 1/2 = Shutter Speed = 1/120

Many motion cameras, especially dSLR, have a shutter speed adjustment on their motion capture, a dial that allows you to change from 1/24 to 1/60 and so on, pretty painlessly — but it is not over cranked!

Let’s do the math:

Frame Rate = 1/24 (aka 24p)
Shutter angle = a/360
Shutter Speed = 1/60

Solve for a:

(1/24) * ( a/360) = 1/60

(24)*1/24 * (a/360) = 1/60 * (24)

(360) * (a/360) = 24/60 (360)

a=144

By now, it can be seen that adjusting the shutter speed does not over crank the camera; what happens? The shutter angle changes, in this case to 144 degree. It’s an acute angle and prevents some motion blur, which will make it easier for Premiere (or any NLE) to interpolate the missing frames.

One last detail since many people are looking for the “film look”: film cameras shoot sync sound at 1/24, with a 180 degree shutter, which when calculated means the shutter is 1/48.

[Sean Winn]

Chris & Richard, thank you for your time.

I think my question was missed though. I’m not looking for info on how to do slo mo, that is not the issue. I was simply wondering if anyone knew, if you shot at 60fps, then dropped it straight into a 24fps timeline, if it ‘deinterlaced’ it in any way. When I try this, the footage plays at normal speed, not slow mo (because I wasn’t wanting to slo it down), but definitely looks deinterlaced – filmic.

That question and the basic question of, if this is possible, and you’re on a shoot where you don’t know which parts you may want to slo down in post, if anyone ever just shoots at 60fps, knowing that in your 24fps timeline, you have the benefit of filmic, normal speed footage once dropped in, or slow it down by changing the frame rate before dropping it in.

[Tero Ahlfors]

[Sean Winn] “if it ‘deinterlaced’ it in any way”

If you’re shooting progressive it doesn’t require deinterlacing. https://en.wikipedia.org/wiki/Interlaced_video

[Chris Tompkins]

Ya, there is no interlace. Your all progressive at 60p and 24p.

So, the answer is yes, you can always shoot 60p, edit in 24p and only slow down what you want.

Just recognize that 60p looks different then 24p, if you want the 24p look, then shoot 24p.

Chris

[Sean Winn]

Thanks again for the replies. You’re right, progressive is not interlaced, my brain was wanting to use the term to describe the look of the footage. It’s interesting, when previewing the 60p clip in the preview window, it’s definitely 60p – the look of live video. When I drop it in the 24 timeline (agian, it’s playing still at normal speed), it now has the look of being shot at 24 – no longer live video. I hadn’t experienced this before.

My whole question was aimed at whether I could avoid having to switch between 60 & 24 frames when I wanted slo mo vs 24. I’ll be on a fast moving, 17hr shoot upcoming (meaning I’m not directing anything, just capturing action as it happens), and there are times it’s a challenge to see everything you’re going to want in the edit.

Thanks again

[Tero Ahlfors]

If you cut a piece of footage to a timeline that has a different frame rate Premiere will automatically add or remove frames to play the footage in the timeline’s frame rate without changing the duration of the original clip. If you interpret the 60 fps footage as 24 it just slows down and the duration will be longer.

[Sean Winn]

Ok, thanks Tero, that explains it then. So, I understand why the 60 dropped in to the 24 looks filmic.

Though on this long shoot it’s tempting to shoot the entire thing at 60 so I have slo mo anywhere I want it, I realize that’s not the way it’s done, so I may just bear switching the mode back & forth – the only problem is the times you miss something because you weren’t ready.

Thanks

[Richard Herd]

Let’s cut right to it: What camera are you shooting with?

This thread has a lot of ambiguities that need fixing.

[Sean Winn]

I shoot with a DSLR workflow (7D/MkIII)