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Canon XH Series HDV Camcorders
Canon XH G1S / G1 (with SDI), Canon XH A1S / A1 (without SDI).


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Old August 25th, 2007, 10:12 AM   #1
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slow motion: 60i or 30f?

I would do a lot slow motion in this video, so I shot in 60i, is it right choice? I always believed that 60i could give smoother slow motion than 30f.
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Old August 25th, 2007, 10:28 AM   #2
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I read something in the Matrox forum. Someone suggested if you want beautiful slow mo footage, shoot in 60i. In post, slow down the clip, copy the same clip to the video track above and "move" 1 one frame to the right. Then set the top track 50% transparent.

I haven't tried that yet.. but it seems cool .. something I will need to try it this weekend.
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Old August 25th, 2007, 10:36 AM   #3
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In Vegas you just "stretch" the clip on the time line.
I have, however, not scientificly evaluated the quality of that function, but it works.

(Working in PAL Land, so I have 25fps)

The "Matrox solution" seems odd - slow motion means that a real-life 10 sec. clip should take pehaps 20 seconds to view. The matrox solution ads 1 frame (1/25th of a second) to the original clip. I wonder if the don't mean "smoothing out" something instead. Superimposing a 50% opacity clip with a 1 frame shift would not mean slow motion, IMHO
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Old August 25th, 2007, 11:03 AM   #4
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Yes Taky, that works. By slowing down the clip and adding the shifted clip above it, it smooths out the interlace artifacts and gives the slo-mo a more natural motion blur effect.
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Old August 25th, 2007, 12:09 PM   #5
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Eric, how can you create slo-mo with a 1-frame shift? That is 1/25th of a sec. longer clip.
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Old August 25th, 2007, 12:23 PM   #6
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Quote:
Originally Posted by Mats Frendahl View Post
Eric, how can you create slo-mo with a 1-frame shift? That is 1/25th of a sec. longer clip.
As mentioned, you must slow it down first.

I've attached a clip with this method. 60i, 50%, HDV to SD.

Done in Vegas using Velocity Envelope set to 50%.
Attached Files
File Type: wmv slomo-60i-frameshift.wmv (765.4 KB, 298 views)
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Old August 25th, 2007, 02:35 PM   #7
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OK - now I see - I read the initial post to quick, skipping the part that the clip was already in slo-mo ;(

OK, so first you set the velocity to 50% on the original clip, then copy the clip to a new track and then shift 1 frame and then set the opacity to 50% on that track.

Correct?

BTW, how much can you slow it down until is looks "strange"?
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Old August 25th, 2007, 02:57 PM   #8
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I dont know why people worry about all the timestretching and all that stuff. If you have access to something like After Effects or some other program that allows deinterlacing with some advanced settings. You can deinterlace 60i footage to 60p and have all those frames to stretch to your hearts content. You'll lose quality deinterlacing yea but not as much as you'd think, its almost minimal. Having 60 frames to play with will give you better slowmo than any other method, guarenteed. 30 frames to play with or would you rather have double...

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Old August 25th, 2007, 03:20 PM   #9
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In PAL Land we do not use 60i, 50i.
But then we have better TV image ... :)
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Old August 25th, 2007, 03:37 PM   #10
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Its no different, the idea is to get as many usable frames as possible before under/overcrank. Meaning 60i you want to deinterlace to 60p, for 50i....50p.
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Old August 28th, 2007, 04:21 AM   #11
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That sounds horrible. Doing two layers and mixing them with eachothers to blend interlacing artifacts? My god. Talk about climbing to the tree with your butt first.

If your doing a 30 fps movie then that 60i clip will give you a perfect 50% slowdown IF your program slows it down properly. Meaning it will take all of those fields and just lay them one by one. No blending, deinterlacing or any of that stuff.

Mind you, even Final Cut Pro and Premiere will do it wrong and everything will look blended and blurred.
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Old August 28th, 2007, 09:56 AM   #12
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It isn't horrible. I do the same thing in order to create a soft/dreamy video. The same trick I learned in Photoshop. Stacking 2 layers of the same video, adjust the top layer style to "screen". Been doing that for quite a while.

Back to slow-mo, I'm using Premiere Pro CS3 with the frame blending feature on. It makes 50% slow mo beautiful already.

Taky
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Old August 28th, 2007, 10:02 AM   #13
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I tested with only stretching compare to stretch + 50% overlay - couldn't see any improvent. Perhaps Vegas does a good job in the first place.
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Old August 28th, 2007, 12:32 PM   #14
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Quote:
Originally Posted by Mikko Lopponen View Post
That sounds horrible. Doing two layers and mixing them with eachothers to blend interlacing artifacts? My god. Talk about climbing to the tree with your butt first.

If your doing a 30 fps movie then that 60i clip will give you a perfect 50% slowdown IF your program slows it down properly. Meaning it will take all of those fields and just lay them one by one. No blending, deinterlacing or any of that stuff.

Mind you, even Final Cut Pro and Premiere will do it wrong and everything will look blended and blurred.

It is not horrible, you have never seen the result so why bash it?
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