Speeding Up High Frame Rate (Slow-Motion) Overcranked Footage (by %)

[Kevin Peeples]

I've searched low and high and I can't seem to find anything. If it's out there, please send my way.

My goal is to take my high frame rate shots that are in slow motion and speed them up so they match visually as if I shot it at 23.98fps. Then when I return my clip to 100% speed, the clip will return to their slow motion state.

The problem is that I've come up with two formulas, each producing different results, and my footage is obscure enough (flames and coolant splashes and laser cutting) that it's hard to tell visually which percentage is the correct percentage to speed up my high frame rate footage to look real-time again.

So here's what I don't have, based on things typically talked about here, here, here, here, and etc:

• I don't have an issue with interpretation or pulldown methods.
• I don't have incorrectly captured footage that I'm trying to problem solve.
• I don't have any audio or audio issues to deal with. This is strictly visual based.
• I don't have a misunderstanding of shooting slo-mo in camera vs. doing it in post.
• I don't have any footage shot at 2:1, HD, ANA or WS ratios. (for those questioning what frame rates I shot at)

Here's what I do have:

• I have .r3d files ranging from 5K to 2K, at a frame base of 23.976fps.
• The Record-Frame-Rate is anywhere from 47.98 to 239.98 based on my format.
• At 100%, all my shots are in slow-motion.
• I have a 23.976fps final timeline.
• All my shots in question are b-roll shots of products, ranging from lathes, mills, water, coolant, fire, welding, sawing, machining, laser fabrication, etc.
• All my shots are captured correctly, at the desired frame rate, and as I watch them, they all play in slow motion as intended.

Before I post my formulas, I'd like to hear if anyone has this mastered, and what your math is. Thanks guys.

 

[Bob Gundu]

IN Redcine-X you can view the meta data of how it was shot. If it's not displayed, click on the cog to display whatever info you need.

 

[Stacey Spears]

If you shot at 47.952, just drop every other frame.

 

[Kevin Peeples]

Okay, I found the Record Frame Rate in the meta settings in REDCINE-X. I somehow missed that after looking through the meta data multiple times before. That still leaves me to find a proper formula to convert a myriad of record frame rates back to real time.

 

[Andy Roberts]

Maybe I'm misunderstanding your request, but the math is pretty straightforward. As a matter of practice, you want to keep it easy on yourself by choosing simple multiples of 24... shoot at 48FPS (2x) or 96FPS (4x) or 192FPS (8x) and then drop frames respectively (drop 50%, 75%, 87.5% of frames) or in other terms, speed it up (200%, 400%, 800%)... Shot rate divided by base rate = speed up %.

239.98FPS would need 90% of the frames dropped or sped up by 1,000%

 

[Kevin Peeples]

Thanks Andy. That math does seem pretty straightforward, its just that my footage is unique enough that those percentages look too fast, visually, which is probably what got me to experiment. I'll trust your math over my eye and see how it goes. It's like hearing a word over and over again and it starts to sound funny.

 

[Bob Gundu]

Thanks Andy. That math does seem pretty straightforward, its just that my footage is unique enough that those percentages look too fast, visually, which is probably what got me to experiment. I'll trust your math over my eye and see how it goes. It's like hearing a word over and over again and it starts to sound funny.

It will look strange primarily because of the lack of motion blur.

 

[Andy Roberts]

One thing happens with over cranked footage is the shutter speed is faster, typically 180 degrees or faster. So the footage will not have the expected 1/48th amount of motion blur. That may give you the feeling that it is playing back faster than real time... almost a strobe effect. Like in the Germania battle scene in Gladiator...

When you slow down high speed footage, you can't really take away the look of high speed shutter, unless you add a motion blur.

 

[Ivan McCullough]

It will look strange primarily because of the lack of motion blur.

Yup, like HFR Hobbit.

I know a flame guy and have had many discussions with him about this. Bottom line, if you want to make it look 'normal' after you speed it up then you will need to apply various different techniques and judge by eye when it looks good to you.

 

[John Snelson]

Its tricking you. It looks too fast at the correct speed because of the lack of motion blur. I deal with it all the time shooting football at 120fps. When you speed it up to 500% it looks too fast

 

[Craig Parkes]

There are motion blur plugins that can be pretty effective in this situation. We have shot high frame rate high shutter angle green screen footage because we were going to need to freeze frame a shot and pull clean keys, then use RMB (real motion blur) plugin for after effects to add the blur back in for the parts of the shot we were wanting it to ramp through.