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60i to 60p vs 30p to 60p for slow motion

FeralDamek

FeralDamek

Hey Indietalk,
I want to achieve the smoothest slow motion possible with the tools that I have.
My camera shoots 24p, 30, and 60i.
In final cut I am able to change 60i and 30p to 60p. I know that it's not "true" 60p obviously, but when I do this and then use optical flow for slomo, the result is a much smoother slomo.
My question to you all is this: Is it better to shoot in 30p and change it to 60p for slomo? Or is it better to shoot in 60i and change it to 60p for slomo?

Thank you.
-Feral
 
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I think you are getting confused with setting the frame rate for final cut and the relevance of Interlace and Progressive... when you set a frame rate in final cut its NOT changing your footage to that frame rate. All you are doing when setting a fps in final cut, you are saying your footage was filmed at ____ so play it back at this speed.
From the sounds of it you are going to want to film at 60i then play this back in at 30i (if ure from the US) this will give you x2 slow down. If you want it to then be progressive, you can de interlace it before export. BUT de interlacing will make footage half res as its copping lines its missing. If you don't get this look up interlace and progressive. However I think im confusing myself now :P
 
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I kinda was under the impression that you needed true 60p (or other higher frame-rates) to get a smooth slo-mo. But I dunno, I could be wrong.

Why don't you try it, then report your results? I'd be at least curious to know.
 
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Just need to define what smooth is? less motion blur? slower slow motion? progressive not interlace? Could be a all of them lol. There is a few ways to do slow motion the most common is filming faster and playing back at normal speeds depending on region. if you filmed at a faster speed and played back at the same speed you would essentially get a 'sharper' look (less motion blur as the shutter is faster)
 
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Jooble said:
Just need to define what smooth is? less motion blur? slower slow motion? progressive not interlace? Could be a all of them lol. There is a few ways to do slow motion the most common is filming faster and playing back at normal speeds depending on region. if you filmed at a faster speed and played back at the same speed you would essentially get a 'sharper' look (less motion blur as the shutter is faster)
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I don't know if there is a standard definition of "smooth", but what I meant, in regards to this conversation, is that it looks fluid, whereas by contrast, 30p, slowed-down to 10p, for example, would not look "smooth" at all.
 
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Going from 60i to 60p will take a "Fundamentally" 30p piece of footage (60i is every other line updated 1/60th of a second - so a full frame refresh every 2i or 1/30th of a second) and slowing it by 50%. Each field (interlaced calls these clumps of even and odd lines fields rather than frames) is a distinct time slice of 1/60th of a second which when combined make up 1/30th of a second with less motion blur each.

Converting 60p to 30p will get you better results as it's taking full frame images each 1/60th rather than half frame images every 1/60th... then stretching them out to fill the 1/30th of a second.

HTH... it can get confusing quickly.
 
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When I change 60i to 60p the speed remains the same, no over cranking.
The only difference is that now each second there are 60 frames instead of 60 fields.
I don't know how final cut pro x achieves this, but it is a noticeable difference.
Now once the footage has been changed to 60p, I am able over crank the footage with optical flow to get smoother slowmo than if I had left it at 60i. The main difference I noticed is significantly less motion blur.
I haven't tried it with 30p to 60p yet, but if I get a moment I will.
 
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Cracker Funk said:
60i isn't 60 fields, but 120, alternating from one to the other.

When you convert 60i to 60p, you're smushing 120 fields together, in order to create 60 complete images.
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I'm pretty sure you're wrong here.

EDIT: Here's a quote from Wikipedia.

60i (actually 59.94, or 60 x 1000/1001 to be more precise; 60 interlaced fields = 30 frames) is an interlaced format and is the standard video field rate per second for NTSC television (e.g. in the US), whether from a broadcast signal, DVD, or home camcorder. This interlaced field rate was developed separately by Farnsworth and Zworykin in 1934,[6] and was part of the NTSC television standards mandated by the FCC in 1941. When NTSC color was introduced in 1953, the older rate of 60 fields per second was reduced by a factor of 1000/1001 to avoid interference between the chroma subcarrier and the broadcast sound carrier.
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Not sure about FCPx, but in previous versions, two tracks of duplicated video both slowed to 50%

Both have a deinterlace filter applied, top even, bottom odd fields...
top has a blink filter applied 1 frame on, 1 frame off.

Done. (although even and odd may be reversed)
 
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SinEater said:
Haha, thanks. I work in the engineering department of a TV station, and my mind was going to be blown if I was wrong.
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Nope. I say dumb stuff, every now and then. :) But in my opinion, I redeem myself by quickly recognizing my mistakes. When I was shooting and editing on miniDV, we didn't ever call it 60i. We called it 30FPS, and interlaced was the only option we had. I just learned that 60i is that same old-school frame-rate.
 
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