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60i captured at 24p?


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#1 Dory Breaux DP

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Posted 15 February 2007 - 06:00 PM

Would it get a slo-mo effect? Would the interlaced image captured in a 24p project in premiere pro 2.0 look wacked out? Should it be captured seperately then de-interlaced?

Thanks,
Dory
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#2 Troy Warr

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Posted 15 February 2007 - 06:42 PM

60i means 60 fields per second, which can later be combined into 30p video. If you put that 30p video on a 24p timeline, you'll get a *slight* slow-motion effect, but it's likely to look more like odd video than the slow-motion effect that you're probably thinking about.

Using a product like Twixtor, you can achieve reasonably good-quality slow-motion effects, but this will come at a price of artifacting and loss of resolution. 60i shoots alternating lines of video 60 times per second, so if you're attempting to use it as 60p (60 complete frames per second), you're missing half the image information so it's going to have to be interpolated or otherwise fudged.

Edited by Troy Warr, 15 February 2007 - 06:43 PM.

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#3 Dory Breaux DP

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Posted 15 February 2007 - 07:04 PM

So 60i is realy just 30fps?

Thanks for that link BTW, that should help some :) .
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#4 Troy Warr

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Posted 15 February 2007 - 07:13 PM

Yeah. I had initially been under the impression, too, that 60i was twice the frames/fields per second as 30i, but they are in fact two terms for the same effective frame rate. I'm not sure if there are some slight differences in terms of "true 30p", e.g. an even 30 frames per second, vs. 29.97 frames per second (NTSC standard), but even if so, their differences would be visually imperceptible.
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#5 Dory Breaux DP

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Posted 15 February 2007 - 07:22 PM

Alright, thanks for clearing that up haha.
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#6 Michael Nash

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Posted 15 February 2007 - 07:50 PM

Yeah. I had initially been under the impression, too, that 60i was twice the frames/fields per second as 30i, but they are in fact two terms for the same effective frame rate. I'm not sure if there are some slight differences in terms of "true 30p", e.g. an even 30 frames per second, vs. 29.97 frames per second (NTSC standard), but even if so, their differences would be visually imperceptible.


NTSC standard is 29.97 interlaced frames per second (59.94 fields per second). "30P" means progressive frames, not interlaced.

There's a significant visual difference between 30 progressive frames and 30 interlaced frames, assuming the interlaced material was captured interlaced (not just 30P material displayed as interlaced). The speed difference between 29.97 and 30 is imperceptible, though.
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#7 Troy Warr

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Posted 15 February 2007 - 08:36 PM

Righto. What I had meant to imply was that I wasn't sure whether 60i actually means that you can create an exact 30 frames per second by recombining fields in post (albeit with interlaced motion artifacts), or whether it's being used in same sense as "30i" is generally used (incorrectly), when the technically correct term would be 59.94i, meaning an effective 29.97 frames per second (if that makes sense).

Michael, do you happen to know if there's technically any difference between 29.97 frames interlaced (NTSC) and 60i - e.g. would the latter literally recombine to 30 fps, or would it still technically be 29.97 fps?
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#8 David Mullen ASC

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Posted 15 February 2007 - 08:43 PM

Shooting at 60i means that motion is sampled 60 times per second, just that each sample is a field instead of a frame (since there are two fields per frame, 60i is also 30 fps - but it is not the same as 30P).

You could convert 60 fields into frames and thus create a 60 fps look when played back in a 24-frame timeline, just that each frame would have less vertical resolution compared to a true progressive-scan captured frame. But often a slow-motion shot has its own reality and one can live with the loss of resolution.

60i is sometimes referred to as "30i" -- hence the confusion, they mean the same thing -- and to make matters more confusing, it's actually 59.94i in NTSC, aka 29.97 fps.
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#9 Michael Nash

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Posted 16 February 2007 - 04:56 AM

Michael, do you happen to know if there's technically any difference between 29.97 frames interlaced (NTSC) and 60i - e.g. would the latter literally recombine to 30 fps, or would it still technically be 29.97 fps?


I think David answered it. NTSC is 29.97 frames per second interlaced, which is sometimes also called 60i. "60i" is the shorthand for NTSC standard def, and also 59.94 interlaced HD. When in doubt, ask or look around to verify if the actual speed is 29.97fps / 59.94 fields/sec; and not running literally 30 progressive fps or 60 progressive fps. Don't always assume that "30fps" means 60i, because it might not (in the case of progressive or film capture).


I hope that makes sense.
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#10 Alecks Purifoy

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Posted 18 February 2007 - 08:15 PM

You can convert your footage to 24p and 30p with a Final Cut or After Effects plug in called "Magic Bullet" by Red Giant software as well as the DV Filmmaker plug in with out looseing too much vertical resolution. Here is a screen shot and a quick run down from, "DEINTERLACING: A DVXuser look at mixing 29.97 into a 23.976 Project" by Jarred Land and Nick Bicanic

Link: http://www.dvxuser.com/articles/60i/



Posted Image


1. Original - The original untouched 29.97 file with full interlacing

2. Vegas - Exporting 23.976 material directly from Vegas 6.0 (by putting a 29.97 clip in a 23.976 timeline directly with no pre-processing)

3. DVFilm maker - DVFilm maker 2.2 output of 23.976 file

4. Magic Bullet output via Plugin through After Effects 6.5
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