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Slowing down 60i footage


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#1 KrisKunz1

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Posted 22 July 2005 - 06:29 PM

We are wanting to shoot something in HD 60i that we will then slow down. I was curious if anyone has tried this or knows anything about it. We are hoping that once slowed down we will still be dealing with a fluid looking picture. Is this even possible and if so, how slow can we go? Thanks.

Kris
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#2 David Mullen ASC

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Posted 22 July 2005 - 06:49 PM

We are wanting to shoot something in HD 60i that we will then slow down.  I was curious if anyone has tried this or knows anything about it.  We are hoping that once slowed down we will still be dealing with a fluid looking picture.  Is this even possible and if so, how slow can we go?  Thanks.

Kris

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Is this for a 24P HD project? Because you can convert 60i into 60P by converting fields into frames, and then play it back at 24P. The result looks no different than shooting at 60P / 60 fps other than the loss of vertical resolution from using half the lines per frame, but motion rendition is the same since you are working with 60 discreet motion samples per second.

If this is for a 60i HD project, then the footage will just be slowed-down in post; you can't create more motion samples per second if more than normal were never recorded. You can use some frame-blending software to remove the steppiness from repeating frames.
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#3 Jaan Shenberger

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Posted 22 July 2005 - 09:53 PM

the best way to do this (without simply sending it off to a good post house), would be to use deinterlacer & twixtor from revisionfx (aftereffects plugins). i can tell you firsthand that they will give you the best 60i to 60p conversion in that price range, and twixtor can usually stretch it beyond that to an interpolated 120 or 180 frames without showing noticeable flaws, though it will largely depend on what kind of motion is in your footage. you can download a demo from their site and fully test to see if it works for you.

hope this helps,
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#4 Thomas Worth

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Posted 24 July 2005 - 03:44 AM

I have written an article about this that will hopefully help you out with this. You can check it out here:

http://rarevision.co...slow_motion.php

David is right -- the camera will, when shooting 60i, capture 60 "half" frames per second (50% of the frame due to interlacing). For the slow motion sequences to look right, however, you should plan your shots and know which ones are going to be slowed so you can set the shutter speed accordingly (to eliminate unnatural motion blur). I suggest a shutter speed of at least 1/120 sec to properly simulate the 180 degree shutter of a film camera so that the effect looks the way most people are familiar with.

I have done some tests with Twixtor but I find that more often than naught the plugin generates weird motion artifacts. You can achieve a really nice slow motion effect without any plugins at all using After Effects. I do, however, recommend the FieldsKit plugin as it's deinterlacing technique is better than the one built into After Effects.
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#5 Tim J Durham

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Posted 24 July 2005 - 07:25 AM

I have written an article about this that will hopefully help you out with this. You can check it out here:

http://rarevision.co...slow_motion.php

David is right -- the camera will, when shooting 60i, capture 60 "half" frames per second (50% of the frame due to interlacing). For the slow motion sequences to look right, however, you should plan your shots and know which ones are going to be slowed so you can set the shutter speed accordingly (to eliminate unnatural motion blur). I suggest a shutter speed of at least 1/120 sec to properly simulate the 180 degree shutter of a film camera so that the effect looks the way most people are familiar with.

I have done some tests with Twixtor but I find that more often than naught the plugin generates weird motion artifacts. You can achieve a really nice slow motion effect without any plugins at all using After Effects. I do, however, recommend the FieldsKit plugin as it's deinterlacing technique is better than the one built into After Effects.

<{POST_SNAPBACK}>

Hey Thomas,
I just read your article and wondered how you'd go about the slo-mo effect if you were working with FCP 4.5? Is there a similar de-interlacer or do I need to spend more $$?

Thanks
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#6 Jaan Shenberger

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Posted 24 July 2005 - 09:19 PM

though i generally agree with thomas's assertion about twixtor's tendency to create strange motion artifacts, i have to say that if you become familiar enough with its features that you can remedy almost any problems that arise with any particular shot when you slow it down. also, i heard that they retooled the pixel-tracking algorithms in the newest version so that it more intelligently discerns seperate layers of motion (which was its biggest flaw), though i haven't used that new version. i'm not connected to revisionfx in any way, but twixtor and fieldskit are plugins that cannot receive enough praise.

Edited by jaan, 24 July 2005 - 09:28 PM.

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